diff --git a/index.html b/index.html
index 3da7c8c..efddd9c 100644
--- a/index.html
+++ b/index.html
@@ -161,6 +161,11 @@ <h3>License</h3>
 <ul>
 <li>The NLESolver-Fortran source code and related files and documentation are distributed under a permissive free software <a href="https://github.com/jacobwilliams/nlesolver-fortran/blob/master/LICENSE">license</a> (BSD-3).</li>
 </ul>
+<h3>References</h3>
+<ul>
+<li>C. G. Broyden, "<a href="https://www.ams.org/journals/mcom/1965-19-092/S0025-5718-1965-0198670-6/S0025-5718-1965-0198670-6.pdf">A Class of Methods for Solving Nonlinear Simultaneous Equations</a>", Math. Comp. 19 (1965), 577-593</li>
+<li>L. K. Schubert, "<a href="https://www.ams.org/journals/mcom/1970-24-109/S0025-5718-1970-0258276-9/S0025-5718-1970-0258276-9.pdf">Modification of a Quasi-Newton Method for Nonlinear Equations with a Sparse Jacobian</a>", Mathematics of Computation, Vol. 24, No. 109 (Jan., 1970), pp. 27-30.</li>
+</ul>
 <h3>See also</h3>
 <ul>
 <li><a href="https://github.com/fortran-lang/minpack">MINPACK</a> -- Modernized Minpack: for solving nonlinear equations and nonlinear least squares problems</li>
diff --git a/interface/export_func.html b/interface/export_func.html
index a1dbf60..beb70c4 100644
--- a/interface/export_func.html
+++ b/interface/export_func.html
@@ -77,7 +77,7 @@ <h1>export_func
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title=" 8.5% of total for procedures.">49 statements</a>
+                 title=" 8.1% of total for procedures.">49 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
diff --git a/interface/func_func.html b/interface/func_func.html
index 002c6b5..646dd23 100644
--- a/interface/func_func.html
+++ b/interface/func_func.html
@@ -77,7 +77,7 @@ <h1>func_func
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title=" 8.5% of total for procedures.">49 statements</a>
+                 title=" 8.1% of total for procedures.">49 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
diff --git a/interface/grad_func.html b/interface/grad_func.html
index ca70f73..57bb5e8 100644
--- a/interface/grad_func.html
+++ b/interface/grad_func.html
@@ -77,7 +77,7 @@ <h1>grad_func
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title=" 8.5% of total for procedures.">49 statements</a>
+                 title=" 8.1% of total for procedures.">49 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
diff --git a/interface/grad_func_sparse.html b/interface/grad_func_sparse.html
index e66ca9d..2e3c4f2 100644
--- a/interface/grad_func_sparse.html
+++ b/interface/grad_func_sparse.html
@@ -77,7 +77,7 @@ <h1>grad_func_sparse
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title=" 8.5% of total for procedures.">49 statements</a>
+                 title=" 8.1% of total for procedures.">49 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
diff --git a/interface/linesearch_func.html b/interface/linesearch_func.html
index 27ed18b..0a7e906 100644
--- a/interface/linesearch_func.html
+++ b/interface/linesearch_func.html
@@ -77,7 +77,7 @@ <h1>linesearch_func
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title=" 8.5% of total for procedures.">49 statements</a>
+                 title=" 8.1% of total for procedures.">49 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
diff --git a/interface/wait_func.html b/interface/wait_func.html
index 10d96c0..eda0945 100644
--- a/interface/wait_func.html
+++ b/interface/wait_func.html
@@ -77,7 +77,7 @@ <h1>wait_func
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title=" 8.5% of total for procedures.">49 statements</a>
+                 title=" 8.1% of total for procedures.">49 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
diff --git a/module/nlesolver_module.html b/module/nlesolver_module.html
index b6f3963..6efaf6d 100644
--- a/module/nlesolver_module.html
+++ b/module/nlesolver_module.html
@@ -77,7 +77,7 @@ <h1>nlesolver_module
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title="100.0% of total for modules and submodules.">686 statements</a>
+                 title="100.0% of total for modules and submodules.">715 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
@@ -240,10 +240,10 @@ <h3 class="card-header card-title bg-light">Uses</h3>
         <ul class="list-group list-group-flush">
             <li class="list-group-item">
               <ul class="list-inline">
+                  <li class="list-inline-item"><a href='https://jacobwilliams.github.io/fmin'>fmin_module</a></li>
                   <li class="list-inline-item"><a href='https://jacobwilliams.github.io/lusol'>lusol_ez_module</a></li>
-                  <li class="list-inline-item"><a href='https://jacobwilliams.github.io/LSQR'>lsqr_module</a></li>
                   <li class="list-inline-item"><a href='http://fortranwiki.org/fortran/show/iso_fortran_env'>iso_fortran_env</a></li>
-                  <li class="list-inline-item"><a href='https://jacobwilliams.github.io/fmin'>fmin_module</a></li>
+                  <li class="list-inline-item"><a href='https://jacobwilliams.github.io/LSQR'>lsqr_module</a></li>
               </ul>
             </li>
             <li class="list-group-item">
@@ -1683,7 +1683,7 @@ <h4>Components</h4>
 <td> =</td>
                 <td>0</td>
             <td>
-
+<a href="../type/nlesolver_type.html#variable-lusol_method" class="pull-right"><emph>Read more&hellip;</emph></a>
             </td>
         </tr>
         <tr>
@@ -2100,7 +2100,7 @@ <h4>Arguments</h4>
             <td>::</td>
             <td><strong>fmin_tol</strong></td>
             <td>
-<p>convergence tolerance for <a>fmin</a> (used when <code>step_mode=3</code>)</p>
+<p>convergence tolerance for <a href="../https:/jacobwilliams.github.io/fmin/proc/fmin.html">fmin</a> (used when <code>step_mode=3</code>)</p>
             </td>
         </tr>
         <tr>
@@ -2468,7 +2468,7 @@ <h4>Arguments</h4>
             <td>::</td>
             <td><strong>lusol_method</strong></td>
             <td>
-
+<p><code>LUSOL</code> method:</p><a href="../proc/initialize_nlesolver_variables.html#variable-lusol_method~2" class="pull-right"><emph>Read more&hellip;</emph></a>
             </td>
         </tr>
     </tbody>
diff --git a/modules.json b/modules.json
new file mode 100644
index 0000000..e21dae8
--- /dev/null
+++ b/modules.json
@@ -0,0 +1 @@
+{"ford-metadata": {"version": "7.0.5"}, "modules": [{"name": "nlesolver_module", "external_url": "./module/nlesolver_module.html", "obj": "module", "pub_procs": {}, "pub_absints": {}, "pub_types": {"nlesolver_type": {"name": "nlesolver_type", "external_url": "./type/nlesolver_type.html", "obj": "type", "extends": null, "variables": [{"name": "n", "external_url": "./type/nlesolver_type.html#variable-n", "obj": "variable", "vartype": "integer", "permission": "private"}, {"name": "m", "external_url": "./type/nlesolver_type.html#variable-m", "obj": "variable", "vartype": "integer", "permission": "private"}, {"name": "max_iter", "external_url": "./type/nlesolver_type.html#variable-max_iter", "obj": "variable", "vartype": "integer", "permission": "private"}, {"name": "tol", "external_url": "./type/nlesolver_type.html#variable-tol", "obj": "variable", "vartype": "real", "permission": "private"}, {"name": "alpha", "external_url": "./type/nlesolver_type.html#variable-alpha", "obj": "variable", 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"vartype": "real", "permission": "private"}, {"name": "conlim", "external_url": "./type/nlesolver_type.html#variable-conlim", "obj": "variable", "vartype": "real", "permission": "private"}, {"name": "itnlim", "external_url": "./type/nlesolver_type.html#variable-itnlim", "obj": "variable", "vartype": "integer", "permission": "private"}, {"name": "nout", "external_url": "./type/nlesolver_type.html#variable-nout", "obj": "variable", "vartype": "integer", "permission": "private"}, {"name": "damp", "external_url": "./type/nlesolver_type.html#variable-damp", "obj": "variable", "vartype": "real", "permission": "private"}, {"name": "lusol_method", "external_url": "./type/nlesolver_type.html#variable-lusol_method", "obj": "variable", "vartype": "integer", "permission": "private"}, {"name": "grad", "external_url": "./type/nlesolver_type.html#variable-grad", "obj": "variable", "vartype": "procedure", "permission": "private"}, {"name": "grad_sparse", "external_url": "./type/nlesolver_type.html#variable-grad_sparse", "obj": "variable", "vartype": "procedure", "permission": "private"}], "boundprocs": [{"name": "initialize", "external_url": "./type/nlesolver_type.html#boundprocedure-initialize", "obj": "boundprocedure", "permission": "public", "generic": "False"}, {"name": "solve", "external_url": "./type/nlesolver_type.html#boundprocedure-solve", "obj": "boundprocedure", "permission": "public", "generic": "False"}, {"name": "destroy", "external_url": "./type/nlesolver_type.html#boundprocedure-destroy", "obj": "boundprocedure", "permission": "public", "generic": "False"}, {"name": "status", "external_url": "./type/nlesolver_type.html#boundprocedure-status", "obj": "boundprocedure", "permission": "public", "generic": "False"}, {"name": "set_status", "external_url": "./type/nlesolver_type.html#boundprocedure-set_status", "obj": "boundprocedure", "permission": "private", "generic": "False"}], "permission": "public"}], "variables": [{"name": "nlesolver_rk", "external_url": "./module/nlesolver_module.html#variable-nlesolver_rk", "obj": "variable", "vartype": "integer", "permission": "public"}, {"name": "wp", "external_url": "./module/nlesolver_module.html#variable-wp", "obj": "variable", "vartype": "integer", "permission": "private"}, {"name": "zero", "external_url": "./module/nlesolver_module.html#variable-zero", "obj": "variable", "vartype": "real", "permission": "private"}, {"name": "one", "external_url": "./module/nlesolver_module.html#variable-one", "obj": "variable", "vartype": "real", "permission": "private"}, {"name": "two", "external_url": "./module/nlesolver_module.html#variable-two", "obj": "variable", "vartype": "real", "permission": "private"}, {"name": "eps", "external_url": "./module/nlesolver_module.html#variable-eps", "obj": "variable", "vartype": "real", "permission": "private"}, {"name": "big", "external_url": "./module/nlesolver_module.html#variable-big", "obj": "variable", "vartype": "real", "permission": "private"}], "permission": "private"}]}
\ No newline at end of file
diff --git a/proc/backtracking_linesearch.html b/proc/backtracking_linesearch.html
index 01b349f..d2a5e22 100644
--- a/proc/backtracking_linesearch.html
+++ b/proc/backtracking_linesearch.html
@@ -77,7 +77,7 @@ <h1>backtracking_linesearch
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title="11.7% of total for procedures.">67 statements</a>
+                 title="11.1% of total for procedures.">67 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
@@ -374,7 +374,7 @@ <h2><span class="anchor" id="src"></span>Source Code</h2>
 <span class="k">        end if</span>
 
 <span class="k">        if</span><span class="w"> </span><span class="p">(((</span><span class="n">f</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">ftmp</span><span class="p">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.0_wp</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">alpha</span><span class="o">*</span><span class="n">t</span><span class="p">)</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">min_alpha_reached</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<span class="k">            if</span><span class="w"> </span><span class="p">(</span><span class="n">min_alpha_reached</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<span class="k">            if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">verbose</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="n">min_alpha_reached</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
 <span class="k">                write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(A)&#39;</span><span class="p">)</span><span class="w"> </span><span class="s1">&#39;        Minimum alpha reached&#39;</span>
 <span class="w">            </span><span class="k">end if</span>
 <span class="w">            </span><span class="c">! Armijo-Goldstein condition is satisfied</span>
diff --git a/proc/exact_linesearch.html b/proc/exact_linesearch.html
index 350b180..c0d142f 100644
--- a/proc/exact_linesearch.html
+++ b/proc/exact_linesearch.html
@@ -77,7 +77,7 @@ <h1>exact_linesearch
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title=" 5.4% of total for procedures.">31 statements</a>
+                 title=" 5.1% of total for procedures.">31 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
diff --git a/proc/fixed_point_linesearch.html b/proc/fixed_point_linesearch.html
index 9f5502f..1b19cd8 100644
--- a/proc/fixed_point_linesearch.html
+++ b/proc/fixed_point_linesearch.html
@@ -77,7 +77,7 @@ <h1>fixed_point_linesearch
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title=" 7.1% of total for procedures.">41 statements</a>
+                 title=" 6.8% of total for procedures.">41 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
diff --git a/proc/get_status.html b/proc/get_status.html
index 7f2b961..f1a09ac 100644
--- a/proc/get_status.html
+++ b/proc/get_status.html
@@ -77,7 +77,7 @@ <h1>get_status
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title=" 2.4% of total for procedures.">14 statements</a>
+                 title=" 2.3% of total for procedures.">14 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
diff --git a/proc/initialize_nlesolver_variables.html b/proc/initialize_nlesolver_variables.html
index 667abe2..63d6a7d 100644
--- a/proc/initialize_nlesolver_variables.html
+++ b/proc/initialize_nlesolver_variables.html
@@ -77,7 +77,7 @@ <h1>initialize_nlesolver_variables
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title="25.0% of total for procedures.">144 statements</a>
+                 title="23.2% of total for procedures.">140 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
@@ -309,7 +309,7 @@ <h3>Arguments</h3>
             <td>::</td>
             <td><strong>fmin_tol</strong></td>
             <td>
-                <p>convergence tolerance for <a>fmin</a> (used when <code>step_mode=3</code>)</p>
+                <p>convergence tolerance for <a href="../https:/jacobwilliams.github.io/fmin/proc/fmin.html">fmin</a> (used when <code>step_mode=3</code>)</p>
             </td>
         </tr>
         <tr>
@@ -691,7 +691,12 @@ <h3>Arguments</h3>
             <td>::</td>
             <td><strong>lusol_method</strong></td>
             <td>
-                
+                <p><code>LUSOL</code> method:</p>
+<ul>
+<li>0 =&gt; TPP: Threshold Partial   Pivoting.</li>
+<li>1 =&gt; TRP: Threshold Rook      Pivoting.</li>
+<li>2 =&gt; TCP: Threshold Complete  Pivoting.</li>
+</ul>
             </td>
         </tr>
     </tbody>
@@ -901,7 +906,11 @@ <h2><span class="anchor" id="src"></span>Source Code</h2>
 <span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">damp</span><span class="w">    </span><span class="c">!! `LSQR`: damp factor</span>
 <span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">itnlim</span><span class="w">  </span><span class="c">!! `LSQR`: max iterations</span>
 <span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">nout</span><span class="w">    </span><span class="c">!! `LSQR`: output unit for printing</span>
-<span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">lusol_method</span>
+<span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">lusol_method</span><span class="w"> </span><span class="c">!! `LUSOL` method:</span>
+<span class="w">                                                      </span><span class="c">!!</span>
+<span class="w">                                                      </span><span class="c">!! * 0 =&gt; TPP: Threshold Partial   Pivoting.</span>
+<span class="w">                                                      </span><span class="c">!! * 1 =&gt; TRP: Threshold Rook      Pivoting.</span>
+<span class="w">                                                      </span><span class="c">!! * 2 =&gt; TCP: Threshold Complete  Pivoting.</span>
 
 <span class="w">    </span><span class="kt">logical</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">status_ok</span><span class="w"> </span><span class="c">!! true if there were no errors</span>
 
@@ -1018,13 +1027,7 @@ <h2><span class="anchor" id="src"></span>Source Code</h2>
 <span class="w">            </span><span class="c">! LUSOL method</span>
 <span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">nout</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">lusol_method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lusol_method</span>
 
-<span class="w">            </span><span class="c">! now now, some options are not available for sparse mode</span>
-<span class="w">            </span><span class="c">!...see if this is possible in sparse mode... TODO</span>
-<span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">use_broyden</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<span class="k">                call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">16</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: broyden method not available for sparse solver&#39;</span><span class="p">)</span>
-<span class="w">                </span><span class="k">return</span>
-<span class="k">            end if</span>
-<span class="k">        end if</span>
+<span class="w">        </span><span class="k">end if</span>
 <span class="k">    end if</span>
 
 <span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">status_ok</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
diff --git a/proc/linear_solver.html b/proc/linear_solver.html
index 22442b1..45689e4 100644
--- a/proc/linear_solver.html
+++ b/proc/linear_solver.html
@@ -77,7 +77,7 @@ <h1>linear_solver
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title="10.4% of total for procedures.">60 statements</a>
+                 title=" 9.9% of total for procedures.">60 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
diff --git a/proc/nlesolver_solver.html b/proc/nlesolver_solver.html
index a71af5c..4ac1471 100644
--- a/proc/nlesolver_solver.html
+++ b/proc/nlesolver_solver.html
@@ -77,7 +77,7 @@ <h1>nlesolver_solver
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title="29.4% of total for procedures.">169 statements</a>
+                 title="33.4% of total for procedures.">202 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
@@ -374,30 +374,34 @@ <h2><span class="anchor" id="src"></span>Source Code</h2>
 <span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
 <span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span>
 
-<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec</span><span class="w">            </span><span class="c">!! function vector</span>
-<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac</span><span class="w">            </span><span class="c">!! jacobian matrix [dense]</span>
-<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="w">  </span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac_sparse</span><span class="w">     </span><span class="c">!! jacobian matrix [sparse]</span>
-<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">rhs</span><span class="w">             </span><span class="c">!! linear system right-hand side</span>
-<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">p</span><span class="w">               </span><span class="c">!! search direction</span>
-<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xold</span><span class="w">            </span><span class="c">!! previous value of `x`</span>
-<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">prev_fvec</span><span class="w">       </span><span class="c">!! previous function vector</span>
-<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">prev_fjac</span><span class="w">       </span><span class="c">!! previous jacobian matrix</span>
-<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">delf</span><span class="w">            </span><span class="c">!! used for Broyden (rank 2 for `matmul`)</span>
-<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">delx</span><span class="w">            </span><span class="c">!! used for Broyden (rank 2 for `matmul`)</span>
-<span class="w">    </span><span class="kt">logical</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">user_stop</span><span class="w">       </span><span class="c">!! user stop button flag</span>
-<span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">info</span><span class="w">            </span><span class="c">!! status flag from the [[linear_solver]]</span>
-<span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">iter</span><span class="w">            </span><span class="c">!! iteration counter</span>
-<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">                            </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span><span class="w">               </span><span class="c">!! magnitude of `fvec`</span>
-<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">                            </span><span class="kd">::</span><span class="w"> </span><span class="n">fold</span><span class="w">            </span><span class="c">!! previous value of `f`</span>
-<span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">n_uphill</span><span class="w">        </span><span class="c">!! number of steps taken in the &quot;uphill&quot; direction</span>
-<span class="w">                                                           </span><span class="c">!! (where `f` is increasing)</span>
-<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">                            </span><span class="kd">::</span><span class="w"> </span><span class="n">delxmag2</span><span class="w">        </span><span class="c">!! used for Broyden</span>
-<span class="w">    </span><span class="kt">logical</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">recompute_jac</span><span class="w">   </span><span class="c">!! if using Broyden, and we want to call the user</span>
-<span class="w">                                                           </span><span class="c">!! jacobian routine instead</span>
-<span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">broyden_counter</span><span class="w"> </span><span class="c">!! number of times the broyden update has been used</span>
-<span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">alloc_stat</span><span class="w">      </span><span class="c">!! allocation status flag</span>
+<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec</span><span class="w">             </span><span class="c">!! function vector</span>
+<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac</span><span class="w">             </span><span class="c">!! jacobian matrix [dense]</span>
+<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="w">  </span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac_sparse</span><span class="w">      </span><span class="c">!! jacobian matrix [sparse]</span>
+<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="w">  </span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">prev_fjac_sparse</span><span class="w"> </span><span class="c">!! previous jacobian matrix [sparse]</span>
+<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">rhs</span><span class="w">              </span><span class="c">!! linear system right-hand side</span>
+<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">p</span><span class="w">                </span><span class="c">!! search direction</span>
+<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xold</span><span class="w">             </span><span class="c">!! previous value of `x`</span>
+<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">prev_fvec</span><span class="w">        </span><span class="c">!! previous function vector</span>
+<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">prev_fjac</span><span class="w">        </span><span class="c">!! previous jacobian matrix</span>
+<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">delf</span><span class="w">             </span><span class="c">!! used for Broyden (rank 2 for `matmul`)</span>
+<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">delx</span><span class="w">             </span><span class="c">!! used for Broyden (rank 2 for `matmul`)</span>
+<span class="w">    </span><span class="kt">logical</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">user_stop</span><span class="w">        </span><span class="c">!! user stop button flag</span>
+<span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">info</span><span class="w">             </span><span class="c">!! status flag from the [[linear_solver]]</span>
+<span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">iter</span><span class="w">             </span><span class="c">!! iteration counter</span>
+<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">                            </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span><span class="w">                </span><span class="c">!! magnitude of `fvec`</span>
+<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">                            </span><span class="kd">::</span><span class="w"> </span><span class="n">fold</span><span class="w">             </span><span class="c">!! previous value of `f`</span>
+<span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">n_uphill</span><span class="w">         </span><span class="c">!! number of steps taken in the &quot;uphill&quot; direction</span>
+<span class="w">                                                            </span><span class="c">!! (where `f` is increasing)</span>
+<span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">                            </span><span class="kd">::</span><span class="w"> </span><span class="n">delxmag2</span><span class="w">         </span><span class="c">!! used for Broyden</span>
+<span class="w">    </span><span class="kt">logical</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">recompute_jac</span><span class="w">    </span><span class="c">!! if using Broyden, and we want to call the user</span>
+<span class="w">                                                            </span><span class="c">!! jacobian routine instead</span>
+<span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">broyden_counter</span><span class="w">  </span><span class="c">!! number of times the broyden update has been used</span>
+<span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">alloc_stat</span><span class="w">       </span><span class="c">!! allocation status flag</span>
 <span class="w">    </span><span class="k">type</span><span class="p">(</span><span class="n">lsqr_solver_ez</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">sparse_solver</span><span class="w">  </span><span class="c">!! sparse LSQR solver class</span>
 <span class="w">    </span><span class="k">type</span><span class="p">(</span><span class="n">lusol_settings</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">lusol_options</span>
+<span class="w">    </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="c">!! counter</span>
+<span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">idx</span><span class="p">,</span><span class="w"> </span><span class="n">index_array</span><span class="w"> </span><span class="c">!! for sparse indexing</span>
+<span class="w">    </span><span class="kt">character</span><span class="p">(</span><span class="nb">len</span><span class="o">=</span><span class="mi">10</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">i_str</span><span class="w"> </span><span class="c">!! string version of `i` for row string</span>
 
 <span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">istat</span><span class="o">&lt;</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="c">! class was not initialized properly</span>
 
@@ -430,6 +434,7 @@ <h2><span class="anchor" id="src"></span>Source Code</h2>
 <span class="w">    </span><span class="k">else</span>
 <span class="w">        </span><span class="c">! sparse</span>
 <span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">fjac_sparse</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n_nonzeros</span><span class="p">)</span><span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">use_broyden</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">prev_fjac_sparse</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n_nonzeros</span><span class="p">)</span><span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
 <span class="w">    </span><span class="k">end if</span>
 
 <span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">rhs</span><span class="w">      </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">)</span><span class="w">      </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
@@ -438,8 +443,11 @@ <h2><span class="anchor" id="src"></span>Source Code</h2>
 <span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">use_broyden</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
 <span class="w">        </span><span class="c">! only need these for broyden:</span>
 <span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">prev_fvec</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">)</span><span class="w">      </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
-<span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">prev_fjac</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
-<span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">delf</span><span class="w">     </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span><span class="w">    </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="o">/=</span><span class="mi">1</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<span class="k">            allocate</span><span class="p">(</span><span class="n">prev_fjac</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<span class="w">            </span><span class="n">index_array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">[(</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n_nonzeros</span><span class="p">)]</span><span class="w"> </span><span class="c">! an array to index the sparse jacobian elements</span>
+<span class="w">        </span><span class="k">end if</span>
+<span class="k">        if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">delf</span><span class="w">     </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span><span class="w">    </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
 <span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">delx</span><span class="w">     </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span><span class="w">    </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
 <span class="w">    </span><span class="k">end if</span>
 <span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">/=</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
@@ -479,8 +487,14 @@ <h2><span class="anchor" id="src"></span>Source Code</h2>
 <span class="k">            if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">use_broyden</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="nb">not</span><span class="p">.</span><span class="w"> </span><span class="n">recompute_jac</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
 <span class="k">                if</span><span class="w"> </span><span class="p">(</span><span class="n">iter</span><span class="o">==</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
 <span class="w">                    </span><span class="c">! always compute Jacobian on the first iteration</span>
-<span class="w">                    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">grad</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fjac</span><span class="p">)</span>
-<span class="w">                    </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
+<span class="w">                    </span><span class="c">!call me%grad(x,fjac)</span>
+<span class="w">                    </span><span class="k">select case</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="p">)</span>
+<span class="w">                    </span><span class="k">case</span><span class="w"> </span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
+<span class="w">                        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">grad</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fjac</span><span class="p">)</span>
+<span class="w">                    </span><span class="k">case</span><span class="w"> </span><span class="p">(</span><span class="mi">2</span><span class="p">:)</span>
+<span class="w">                        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">grad_sparse</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
+<span class="w">                    </span><span class="k">end select</span>
+<span class="k">                    </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
 <span class="w">                </span><span class="k">else</span>
 <span class="w">                    </span><span class="c">! and use Broyden update to estimate Jacobian</span>
 <span class="w">                    </span><span class="c">! for subsequent iterations.</span>
@@ -488,24 +502,56 @@ <h2><span class="anchor" id="src"></span>Source Code</h2>
 <span class="w">                    </span><span class="c">! note: fvec was computed the last iteration</span>
 <span class="w">                    </span><span class="n">delx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">xold</span>
 <span class="w">                    </span><span class="n">delf</span><span class="p">(:,</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fvec</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">prev_fvec</span>
-<span class="w">                    </span><span class="n">delxmag2</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="nb">dot_product</span><span class="p">(</span><span class="n">delx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">),</span><span class="n">delx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">))</span>
 
-<span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">delxmag2</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">eps</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<span class="k">                        call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
-<span class="w">                                </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: Divide by zero when computing Broyden update&#39;</span><span class="p">)</span>
-<span class="w">                        </span><span class="k">exit</span>
-<span class="k">                    end if</span>
+<span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="o">==</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="k">then</span><span class="w"> </span><span class="c">! dense</span>
+
+<span class="w">                        </span><span class="n">delxmag2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">dot_product</span><span class="p">(</span><span class="n">delx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">),</span><span class="n">delx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">))</span>
+<span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">delxmag2</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">eps</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<span class="k">                            call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
+<span class="w">                                    </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: Divide by zero when computing Broyden update&#39;</span><span class="p">)</span>
+<span class="w">                            </span><span class="k">exit</span>
+<span class="k">                        end if</span>
+
+<span class="w">                        </span><span class="c">! Jacobian estimate:</span>
+<span class="w">                        </span><span class="c">! This is the equation from wikipedia : https://en.wikipedia.org/wiki/Broyden%27s_method</span>
+<span class="w">                        </span><span class="n">fjac</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">prev_fjac</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nb">matmul</span><span class="p">((</span><span class="n">delf</span><span class="o">-</span><span class="nb">matmul</span><span class="p">(</span><span class="n">prev_fjac</span><span class="p">,</span><span class="n">delx</span><span class="p">)),</span><span class="w"> </span><span class="nb">transpose</span><span class="p">(</span><span class="n">delx</span><span class="p">))</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">delxmag2</span>
+
+<span class="w">                        </span><span class="c">! see also: eqn 4 in Schubert, which is different ...</span>
+
+<span class="w">                    </span><span class="k">else</span><span class="w"> </span><span class="c">! using a sparse option</span>
 
-<span class="w">                    </span><span class="c">! Jacobian estimate:</span>
-<span class="w">                    </span><span class="n">fjac</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">prev_fjac</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">&amp;</span>
-<span class="w">                           </span><span class="nb">matmul</span><span class="p">((</span><span class="n">delf</span><span class="o">-</span><span class="nb">matmul</span><span class="p">(</span><span class="n">prev_fjac</span><span class="p">,</span><span class="n">delx</span><span class="p">)),&amp;</span>
-<span class="w">                           </span><span class="nb">transpose</span><span class="p">(</span><span class="n">delx</span><span class="p">))</span><span class="o">/</span><span class="n">delxmag2</span>
+<span class="w">                        </span><span class="c">! Just a row-by-row version of the fjac equation above.</span>
+<span class="w">                        </span><span class="c">! see L.K. Schubert, 1970</span>
+<span class="w">                        </span><span class="k">do </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">m</span>
 
-<span class="w">                    </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span>
+<span class="w">                            </span><span class="n">idx</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">pack</span><span class="p">(</span><span class="n">index_array</span><span class="p">,</span><span class="w"> </span><span class="n">mask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">irow</span><span class="o">==</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="c">! the nonzero elements in this row</span>
+<span class="w">                            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">size</span><span class="p">(</span><span class="n">idx</span><span class="p">)</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">cycle</span><span class="w"> </span><span class="c">! no non-zeros in this row</span>
+
+<span class="w">                            </span><span class="k">associate</span><span class="w"> </span><span class="p">(</span><span class="n">dx</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">delx</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="p">(</span><span class="n">idx</span><span class="p">),:))</span><span class="w"> </span><span class="c">! nonzero x vec for this row</span>
+<span class="w">                                </span><span class="n">delxmag2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">dot_product</span><span class="p">(</span><span class="n">dx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">),</span><span class="n">dx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">))</span><span class="w"> </span><span class="c">! only those x&#39;s for this row</span>
+<span class="w">                                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">delxmag2</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">eps</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<span class="k">                                    write</span><span class="p">(</span><span class="n">i_str</span><span class="p">,</span><span class="s1">&#39;(I10)&#39;</span><span class="p">)</span><span class="w"> </span><span class="n">i</span>
+<span class="w">                                    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
+<span class="w">                                            </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: Divide by zero when computing sparse Broyden update for row &#39;</span><span class="o">//</span><span class="p">&amp;</span>
+<span class="w">                                            </span><span class="nb">trim</span><span class="p">(</span><span class="nb">adjustl</span><span class="p">(</span><span class="n">i_str</span><span class="p">)))</span>
+<span class="w">                                    </span><span class="k">exit</span>
+<span class="k">                                end if</span>
+<span class="k">                                </span><span class="n">fjac_sparse</span><span class="p">(</span><span class="n">idx</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">prev_fjac_sparse</span><span class="p">(</span><span class="n">idx</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">&amp;</span>
+<span class="w">                                        </span><span class="nb">matmul</span><span class="p">((</span><span class="n">delf</span><span class="p">(</span><span class="n">i</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span><span class="o">-</span><span class="nb">matmul</span><span class="p">(</span><span class="n">prev_fjac_sparse</span><span class="p">(</span><span class="n">idx</span><span class="p">),</span><span class="n">dx</span><span class="p">)),</span><span class="w"> </span><span class="nb">transpose</span><span class="p">(</span><span class="n">dx</span><span class="p">))</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">delxmag2</span>
+<span class="w">                            </span><span class="k">end associate</span>
+
+<span class="k">                        end do</span>
+
+<span class="k">                    end if</span>
+<span class="k">                    </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span>
 <span class="w">                </span><span class="k">end if</span>
-<span class="k">                </span><span class="n">prev_fjac</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fjac</span>
-<span class="w">                </span><span class="n">prev_fvec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fvec</span>
-<span class="w">            </span><span class="k">else</span>
+<span class="k">                </span><span class="n">prev_fvec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fvec</span>
+<span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="o">==</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<span class="k">                    </span><span class="n">prev_fjac</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fjac</span>
+<span class="w">                </span><span class="k">else</span>
+<span class="k">                    </span><span class="n">prev_fjac_sparse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fjac_sparse</span>
+<span class="w">                </span><span class="k">end if</span>
+<span class="k">            else</span>
 <span class="w">                </span><span class="c">! compute the jacobian:</span>
 <span class="w">                </span><span class="k">select case</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="p">)</span>
 <span class="w">                </span><span class="k">case</span><span class="w"> </span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
@@ -551,11 +597,8 @@ <h2><span class="anchor" id="src"></span>Source Code</h2>
 <span class="k">            case</span><span class="w"> </span><span class="p">(</span><span class="mi">3</span><span class="p">)</span>
 <span class="w">                </span><span class="c">! use lusol solver</span>
 <span class="w">                </span><span class="n">lusol_options</span><span class="p">%</span><span class="n">method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">lusol_method</span>
-<span class="w">                    </span><span class="c">! 0    =&gt;  TPP: Threshold Partial   Pivoting.</span>
-<span class="w">                    </span><span class="c">! 1    =&gt;  TRP: Threshold Rook      Pivoting.</span>
-<span class="w">                    </span><span class="c">! 2    =&gt;  TCP: Threshold Complete  Pivoting.</span>
 <span class="w">                </span><span class="k">call </span><span class="n">solve</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n_nonzeros</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">irow</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">,</span><span class="n">rhs</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">info</span><span class="p">,&amp;</span>
-<span class="w">                            </span><span class="n">settings</span><span class="o">=</span><span class="n">lusol_options</span><span class="p">)</span>
+<span class="w">                           </span><span class="n">settings</span><span class="o">=</span><span class="n">lusol_options</span><span class="p">)</span>
 <span class="w">            </span><span class="k">end select</span>
 
 <span class="w">            </span><span class="c">! check for errors:</span>
diff --git a/proc/set_status.html b/proc/set_status.html
index 1c08975..c815ddf 100644
--- a/proc/set_status.html
+++ b/proc/set_status.html
@@ -77,7 +77,7 @@ <h1>set_status
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title=" 5.0% of total for procedures.">29 statements</a>
+                 title=" 4.8% of total for procedures.">29 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
diff --git a/proc/simple_step.html b/proc/simple_step.html
index b8a6981..680a3af 100644
--- a/proc/simple_step.html
+++ b/proc/simple_step.html
@@ -77,7 +77,7 @@ <h1>simple_step
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title=" 2.4% of total for procedures.">14 statements</a>
+                 title=" 2.3% of total for procedures.">14 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
diff --git a/sourcefile/nlesolver_module.f90.html b/sourcefile/nlesolver_module.f90.html
index d7bfda9..126e309 100644
--- a/sourcefile/nlesolver_module.f90.html
+++ b/sourcefile/nlesolver_module.f90.html
@@ -77,7 +77,7 @@ <h1>nlesolver_module.F90
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title="100.0% of total for source files.">686 statements</a>
+                 title="100.0% of total for source files.">715 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
@@ -279,384 +279,384 @@ <h2><span class="anchor" id="src"></span>Source Code</h2>
 <a id="ln-123" name="ln-123" href="#ln-123"></a><span class="w">        </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">damp</span><span class="w">    </span><span class="o">=</span><span class="w"> </span><span class="n">zero</span><span class="w">  </span><span class="c">!! damp parameter for LSQR</span>
 <a id="ln-124" name="ln-124" href="#ln-124"></a>
 <a id="ln-125" name="ln-125" href="#ln-125"></a><span class="w">        </span><span class="c">! LUSOL parameters:</span>
-<a id="ln-126" name="ln-126" href="#ln-126"></a><span class="w">        </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">lusol_method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
-<a id="ln-127" name="ln-127" href="#ln-127"></a>
-<a id="ln-128" name="ln-128" href="#ln-128"></a><span class="w">        </span><span class="c">! dense version:</span>
-<a id="ln-129" name="ln-129" href="#ln-129"></a><span class="w">        </span><span class="k">procedure</span><span class="p">(</span><span class="n">grad_func</span><span class="p">),</span><span class="k">pointer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">grad</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="nb">null</span><span class="p">()</span><span class="w"> </span><span class="c">!! user-supplied routine to compute the gradient of the function (dense version)</span>
-<a id="ln-130" name="ln-130" href="#ln-130"></a>
-<a id="ln-131" name="ln-131" href="#ln-131"></a><span class="w">        </span><span class="c">! sparse version:</span>
-<a id="ln-132" name="ln-132" href="#ln-132"></a><span class="w">        </span><span class="k">procedure</span><span class="p">(</span><span class="n">grad_func_sparse</span><span class="p">),</span><span class="k">pointer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">grad_sparse</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="nb">null</span><span class="p">()</span><span class="w"> </span><span class="c">!! user-supplied routine to compute the gradient of the function (sparse version)</span>
-<a id="ln-133" name="ln-133" href="#ln-133"></a>
-<a id="ln-134" name="ln-134" href="#ln-134"></a><span class="w">        </span><span class="k">contains</span>
+<a id="ln-126" name="ln-126" href="#ln-126"></a><span class="w">        </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">lusol_method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="c">!! * 0 =&gt; TPP: Threshold Partial   Pivoting.</span>
+<a id="ln-127" name="ln-127" href="#ln-127"></a><span class="w">                                    </span><span class="c">!! * 1 =&gt; TRP: Threshold Rook      Pivoting.</span>
+<a id="ln-128" name="ln-128" href="#ln-128"></a><span class="w">                                    </span><span class="c">!! * 2 =&gt; TCP: Threshold Complete  Pivoting.</span>
+<a id="ln-129" name="ln-129" href="#ln-129"></a>
+<a id="ln-130" name="ln-130" href="#ln-130"></a><span class="w">        </span><span class="c">! dense version:</span>
+<a id="ln-131" name="ln-131" href="#ln-131"></a><span class="w">        </span><span class="k">procedure</span><span class="p">(</span><span class="n">grad_func</span><span class="p">),</span><span class="k">pointer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">grad</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="nb">null</span><span class="p">()</span><span class="w"> </span><span class="c">!! user-supplied routine to compute the gradient of the function (dense version)</span>
+<a id="ln-132" name="ln-132" href="#ln-132"></a>
+<a id="ln-133" name="ln-133" href="#ln-133"></a><span class="w">        </span><span class="c">! sparse version:</span>
+<a id="ln-134" name="ln-134" href="#ln-134"></a><span class="w">        </span><span class="k">procedure</span><span class="p">(</span><span class="n">grad_func_sparse</span><span class="p">),</span><span class="k">pointer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">grad_sparse</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="nb">null</span><span class="p">()</span><span class="w"> </span><span class="c">!! user-supplied routine to compute the gradient of the function (sparse version)</span>
 <a id="ln-135" name="ln-135" href="#ln-135"></a>
-<a id="ln-136" name="ln-136" href="#ln-136"></a><span class="k">        private</span>
+<a id="ln-136" name="ln-136" href="#ln-136"></a><span class="w">        </span><span class="k">contains</span>
 <a id="ln-137" name="ln-137" href="#ln-137"></a>
-<a id="ln-138" name="ln-138" href="#ln-138"></a><span class="k">        procedure</span><span class="p">,</span><span class="k">public</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">initialize</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">initialize_nlesolver_variables</span>
-<a id="ln-139" name="ln-139" href="#ln-139"></a><span class="w">        </span><span class="k">procedure</span><span class="p">,</span><span class="k">public</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">solve</span><span class="w">      </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">nlesolver_solver</span>
-<a id="ln-140" name="ln-140" href="#ln-140"></a><span class="w">        </span><span class="k">procedure</span><span class="p">,</span><span class="k">public</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">destroy</span><span class="w">    </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">destroy_nlesolver_variables</span>
-<a id="ln-141" name="ln-141" href="#ln-141"></a><span class="w">        </span><span class="k">procedure</span><span class="p">,</span><span class="k">public</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">status</span><span class="w">     </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">get_status</span>
-<a id="ln-142" name="ln-142" href="#ln-142"></a>
-<a id="ln-143" name="ln-143" href="#ln-143"></a><span class="w">        </span><span class="k">procedure</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">set_status</span>
+<a id="ln-138" name="ln-138" href="#ln-138"></a><span class="k">        private</span>
+<a id="ln-139" name="ln-139" href="#ln-139"></a>
+<a id="ln-140" name="ln-140" href="#ln-140"></a><span class="k">        procedure</span><span class="p">,</span><span class="k">public</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">initialize</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">initialize_nlesolver_variables</span>
+<a id="ln-141" name="ln-141" href="#ln-141"></a><span class="w">        </span><span class="k">procedure</span><span class="p">,</span><span class="k">public</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">solve</span><span class="w">      </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">nlesolver_solver</span>
+<a id="ln-142" name="ln-142" href="#ln-142"></a><span class="w">        </span><span class="k">procedure</span><span class="p">,</span><span class="k">public</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">destroy</span><span class="w">    </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">destroy_nlesolver_variables</span>
+<a id="ln-143" name="ln-143" href="#ln-143"></a><span class="w">        </span><span class="k">procedure</span><span class="p">,</span><span class="k">public</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">status</span><span class="w">     </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">get_status</span>
 <a id="ln-144" name="ln-144" href="#ln-144"></a>
-<a id="ln-145" name="ln-145" href="#ln-145"></a><span class="w">        </span><span class="k">end type </span><span class="n">nlesolver_type</span>
-<a id="ln-146" name="ln-146" href="#ln-146"></a><span class="w">    </span><span class="c">!*********************************************************</span>
-<a id="ln-147" name="ln-147" href="#ln-147"></a>
-<a id="ln-148" name="ln-148" href="#ln-148"></a><span class="w">    </span><span class="k">abstract interface</span>
+<a id="ln-145" name="ln-145" href="#ln-145"></a><span class="w">        </span><span class="k">procedure</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">set_status</span>
+<a id="ln-146" name="ln-146" href="#ln-146"></a>
+<a id="ln-147" name="ln-147" href="#ln-147"></a><span class="w">        </span><span class="k">end type </span><span class="n">nlesolver_type</span>
+<a id="ln-148" name="ln-148" href="#ln-148"></a><span class="w">    </span><span class="c">!*********************************************************</span>
 <a id="ln-149" name="ln-149" href="#ln-149"></a>
-<a id="ln-150" name="ln-150" href="#ln-150"></a><span class="k">        subroutine </span><span class="n">func_func</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">)</span>
-<a id="ln-151" name="ln-151" href="#ln-151"></a><span class="w">            </span><span class="c">!! compute the function</span>
-<a id="ln-152" name="ln-152" href="#ln-152"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span><span class="p">,</span><span class="n">nlesolver_type</span>
-<a id="ln-153" name="ln-153" href="#ln-153"></a><span class="w">            </span><span class="k">implicit none</span>
-<a id="ln-154" name="ln-154" href="#ln-154"></a><span class="k">            class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
-<a id="ln-155" name="ln-155" href="#ln-155"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">    </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span>
-<a id="ln-156" name="ln-156" href="#ln-156"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span>
-<a id="ln-157" name="ln-157" href="#ln-157"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">func_func</span>
-<a id="ln-158" name="ln-158" href="#ln-158"></a>
-<a id="ln-159" name="ln-159" href="#ln-159"></a><span class="w">        </span><span class="k">subroutine </span><span class="n">grad_func</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">g</span><span class="p">)</span>
-<a id="ln-160" name="ln-160" href="#ln-160"></a><span class="w">            </span><span class="c">!! compute the gradient of the function (Jacobian). Dense version.</span>
-<a id="ln-161" name="ln-161" href="#ln-161"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span><span class="p">,</span><span class="n">nlesolver_type</span>
-<a id="ln-162" name="ln-162" href="#ln-162"></a><span class="w">            </span><span class="k">implicit none</span>
-<a id="ln-163" name="ln-163" href="#ln-163"></a><span class="k">            class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
-<a id="ln-164" name="ln-164" href="#ln-164"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">    </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span>
-<a id="ln-165" name="ln-165" href="#ln-165"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">g</span>
-<a id="ln-166" name="ln-166" href="#ln-166"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">grad_func</span>
-<a id="ln-167" name="ln-167" href="#ln-167"></a>
-<a id="ln-168" name="ln-168" href="#ln-168"></a><span class="w">        </span><span class="k">subroutine </span><span class="n">grad_func_sparse</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">g</span><span class="p">)</span>
-<a id="ln-169" name="ln-169" href="#ln-169"></a><span class="w">            </span><span class="c">!! compute the gradient of the function (Jacobian). Sparse version.</span>
-<a id="ln-170" name="ln-170" href="#ln-170"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span><span class="p">,</span><span class="n">nlesolver_type</span>
-<a id="ln-171" name="ln-171" href="#ln-171"></a><span class="w">            </span><span class="k">implicit none</span>
-<a id="ln-172" name="ln-172" href="#ln-172"></a><span class="k">            class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
-<a id="ln-173" name="ln-173" href="#ln-173"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">  </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span>
-<a id="ln-174" name="ln-174" href="#ln-174"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">g</span><span class="w"> </span><span class="c">!! sparse jacobian. length is `n_nonzeros`</span>
-<a id="ln-175" name="ln-175" href="#ln-175"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">grad_func_sparse</span>
-<a id="ln-176" name="ln-176" href="#ln-176"></a>
-<a id="ln-177" name="ln-177" href="#ln-177"></a><span class="w">        </span><span class="k">subroutine </span><span class="n">export_func</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">,</span><span class="n">iter</span><span class="p">)</span>
-<a id="ln-178" name="ln-178" href="#ln-178"></a><span class="w">            </span><span class="c">!! export an iteration:</span>
-<a id="ln-179" name="ln-179" href="#ln-179"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span><span class="p">,</span><span class="n">nlesolver_type</span>
-<a id="ln-180" name="ln-180" href="#ln-180"></a><span class="w">            </span><span class="k">implicit none</span>
-<a id="ln-181" name="ln-181" href="#ln-181"></a><span class="k">            class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
-<a id="ln-182" name="ln-182" href="#ln-182"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">    </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span>
-<a id="ln-183" name="ln-183" href="#ln-183"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">    </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span>
-<a id="ln-184" name="ln-184" href="#ln-184"></a><span class="w">            </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">                  </span><span class="kd">::</span><span class="w"> </span><span class="n">iter</span><span class="w"> </span><span class="c">!! iteration number</span>
-<a id="ln-185" name="ln-185" href="#ln-185"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">export_func</span>
-<a id="ln-186" name="ln-186" href="#ln-186"></a>
-<a id="ln-187" name="ln-187" href="#ln-187"></a><span class="w">        </span><span class="k">subroutine </span><span class="n">wait_func</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">user_stop</span><span class="p">)</span>
-<a id="ln-188" name="ln-188" href="#ln-188"></a><span class="w">            </span><span class="c">!! enable a user-triggered stop of the iterations:</span>
-<a id="ln-189" name="ln-189" href="#ln-189"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span><span class="p">,</span><span class="n">nlesolver_type</span>
-<a id="ln-190" name="ln-190" href="#ln-190"></a><span class="w">            </span><span class="k">implicit none</span>
-<a id="ln-191" name="ln-191" href="#ln-191"></a><span class="k">            class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
-<a id="ln-192" name="ln-192" href="#ln-192"></a><span class="w">            </span><span class="kt">logical</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w">                 </span><span class="kd">::</span><span class="w"> </span><span class="n">user_stop</span>
-<a id="ln-193" name="ln-193" href="#ln-193"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">wait_func</span>
-<a id="ln-194" name="ln-194" href="#ln-194"></a>
-<a id="ln-195" name="ln-195" href="#ln-195"></a><span class="w">        </span><span class="k">subroutine </span><span class="n">linesearch_func</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">xold</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">fjac</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
-<a id="ln-196" name="ln-196" href="#ln-196"></a><span class="w">            </span><span class="c">!! line search method. Note that not all inputs/outputs are</span>
-<a id="ln-197" name="ln-197" href="#ln-197"></a><span class="w">            </span><span class="c">!! used by all methods.</span>
-<a id="ln-198" name="ln-198" href="#ln-198"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span><span class="p">,</span><span class="n">nlesolver_type</span>
-<a id="ln-199" name="ln-199" href="#ln-199"></a><span class="w">            </span><span class="k">implicit none</span>
-<a id="ln-200" name="ln-200" href="#ln-200"></a><span class="k">            class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
-<a id="ln-201" name="ln-201" href="#ln-201"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xold</span><span class="w">      </span><span class="c">!! previous value of `x`</span>
-<a id="ln-202" name="ln-202" href="#ln-202"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">p</span><span class="w">         </span><span class="c">!! search direction</span>
-<a id="ln-203" name="ln-203" href="#ln-203"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span><span class="w">        </span><span class="c">!! new `x`</span>
-<a id="ln-204" name="ln-204" href="#ln-204"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span><span class="w">                      </span><span class="c">!! * input: current magnitude of `fvec`,</span>
-<a id="ln-205" name="ln-205" href="#ln-205"></a><span class="w">                                                             </span><span class="c">!! * output: new value of `f`</span>
-<a id="ln-206" name="ln-206" href="#ln-206"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec</span><span class="w">   </span><span class="c">!! * input: current function vector,</span>
-<a id="ln-207" name="ln-207" href="#ln-207"></a><span class="w">                                                             </span><span class="c">!! * output: new function vector</span>
-<a id="ln-208" name="ln-208" href="#ln-208"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac</span><span class="w"> </span><span class="c">!! jacobian matrix [dense]</span>
-<a id="ln-209" name="ln-209" href="#ln-209"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac_sparse</span><span class="w"> </span><span class="c">!! jacobian matrix [sparse]</span>
-<a id="ln-210" name="ln-210" href="#ln-210"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">linesearch_func</span>
-<a id="ln-211" name="ln-211" href="#ln-211"></a>
-<a id="ln-212" name="ln-212" href="#ln-212"></a><span class="w">    </span><span class="k">end interface</span>
+<a id="ln-150" name="ln-150" href="#ln-150"></a><span class="w">    </span><span class="k">abstract interface</span>
+<a id="ln-151" name="ln-151" href="#ln-151"></a>
+<a id="ln-152" name="ln-152" href="#ln-152"></a><span class="k">        subroutine </span><span class="n">func_func</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">)</span>
+<a id="ln-153" name="ln-153" href="#ln-153"></a><span class="w">            </span><span class="c">!! compute the function</span>
+<a id="ln-154" name="ln-154" href="#ln-154"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span><span class="p">,</span><span class="n">nlesolver_type</span>
+<a id="ln-155" name="ln-155" href="#ln-155"></a><span class="w">            </span><span class="k">implicit none</span>
+<a id="ln-156" name="ln-156" href="#ln-156"></a><span class="k">            class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-157" name="ln-157" href="#ln-157"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">    </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span>
+<a id="ln-158" name="ln-158" href="#ln-158"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span>
+<a id="ln-159" name="ln-159" href="#ln-159"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">func_func</span>
+<a id="ln-160" name="ln-160" href="#ln-160"></a>
+<a id="ln-161" name="ln-161" href="#ln-161"></a><span class="w">        </span><span class="k">subroutine </span><span class="n">grad_func</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">g</span><span class="p">)</span>
+<a id="ln-162" name="ln-162" href="#ln-162"></a><span class="w">            </span><span class="c">!! compute the gradient of the function (Jacobian). Dense version.</span>
+<a id="ln-163" name="ln-163" href="#ln-163"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span><span class="p">,</span><span class="n">nlesolver_type</span>
+<a id="ln-164" name="ln-164" href="#ln-164"></a><span class="w">            </span><span class="k">implicit none</span>
+<a id="ln-165" name="ln-165" href="#ln-165"></a><span class="k">            class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-166" name="ln-166" href="#ln-166"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">    </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span>
+<a id="ln-167" name="ln-167" href="#ln-167"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">g</span>
+<a id="ln-168" name="ln-168" href="#ln-168"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">grad_func</span>
+<a id="ln-169" name="ln-169" href="#ln-169"></a>
+<a id="ln-170" name="ln-170" href="#ln-170"></a><span class="w">        </span><span class="k">subroutine </span><span class="n">grad_func_sparse</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">g</span><span class="p">)</span>
+<a id="ln-171" name="ln-171" href="#ln-171"></a><span class="w">            </span><span class="c">!! compute the gradient of the function (Jacobian). Sparse version.</span>
+<a id="ln-172" name="ln-172" href="#ln-172"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span><span class="p">,</span><span class="n">nlesolver_type</span>
+<a id="ln-173" name="ln-173" href="#ln-173"></a><span class="w">            </span><span class="k">implicit none</span>
+<a id="ln-174" name="ln-174" href="#ln-174"></a><span class="k">            class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-175" name="ln-175" href="#ln-175"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">  </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span>
+<a id="ln-176" name="ln-176" href="#ln-176"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">g</span><span class="w"> </span><span class="c">!! sparse jacobian. length is `n_nonzeros`</span>
+<a id="ln-177" name="ln-177" href="#ln-177"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">grad_func_sparse</span>
+<a id="ln-178" name="ln-178" href="#ln-178"></a>
+<a id="ln-179" name="ln-179" href="#ln-179"></a><span class="w">        </span><span class="k">subroutine </span><span class="n">export_func</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">,</span><span class="n">iter</span><span class="p">)</span>
+<a id="ln-180" name="ln-180" href="#ln-180"></a><span class="w">            </span><span class="c">!! export an iteration:</span>
+<a id="ln-181" name="ln-181" href="#ln-181"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span><span class="p">,</span><span class="n">nlesolver_type</span>
+<a id="ln-182" name="ln-182" href="#ln-182"></a><span class="w">            </span><span class="k">implicit none</span>
+<a id="ln-183" name="ln-183" href="#ln-183"></a><span class="k">            class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-184" name="ln-184" href="#ln-184"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">    </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span>
+<a id="ln-185" name="ln-185" href="#ln-185"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">    </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span>
+<a id="ln-186" name="ln-186" href="#ln-186"></a><span class="w">            </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">                  </span><span class="kd">::</span><span class="w"> </span><span class="n">iter</span><span class="w"> </span><span class="c">!! iteration number</span>
+<a id="ln-187" name="ln-187" href="#ln-187"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">export_func</span>
+<a id="ln-188" name="ln-188" href="#ln-188"></a>
+<a id="ln-189" name="ln-189" href="#ln-189"></a><span class="w">        </span><span class="k">subroutine </span><span class="n">wait_func</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">user_stop</span><span class="p">)</span>
+<a id="ln-190" name="ln-190" href="#ln-190"></a><span class="w">            </span><span class="c">!! enable a user-triggered stop of the iterations:</span>
+<a id="ln-191" name="ln-191" href="#ln-191"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span><span class="p">,</span><span class="n">nlesolver_type</span>
+<a id="ln-192" name="ln-192" href="#ln-192"></a><span class="w">            </span><span class="k">implicit none</span>
+<a id="ln-193" name="ln-193" href="#ln-193"></a><span class="k">            class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-194" name="ln-194" href="#ln-194"></a><span class="w">            </span><span class="kt">logical</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w">                 </span><span class="kd">::</span><span class="w"> </span><span class="n">user_stop</span>
+<a id="ln-195" name="ln-195" href="#ln-195"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">wait_func</span>
+<a id="ln-196" name="ln-196" href="#ln-196"></a>
+<a id="ln-197" name="ln-197" href="#ln-197"></a><span class="w">        </span><span class="k">subroutine </span><span class="n">linesearch_func</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">xold</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">fjac</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
+<a id="ln-198" name="ln-198" href="#ln-198"></a><span class="w">            </span><span class="c">!! line search method. Note that not all inputs/outputs are</span>
+<a id="ln-199" name="ln-199" href="#ln-199"></a><span class="w">            </span><span class="c">!! used by all methods.</span>
+<a id="ln-200" name="ln-200" href="#ln-200"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span><span class="p">,</span><span class="n">nlesolver_type</span>
+<a id="ln-201" name="ln-201" href="#ln-201"></a><span class="w">            </span><span class="k">implicit none</span>
+<a id="ln-202" name="ln-202" href="#ln-202"></a><span class="k">            class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-203" name="ln-203" href="#ln-203"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xold</span><span class="w">      </span><span class="c">!! previous value of `x`</span>
+<a id="ln-204" name="ln-204" href="#ln-204"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">p</span><span class="w">         </span><span class="c">!! search direction</span>
+<a id="ln-205" name="ln-205" href="#ln-205"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span><span class="w">        </span><span class="c">!! new `x`</span>
+<a id="ln-206" name="ln-206" href="#ln-206"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span><span class="w">                      </span><span class="c">!! * input: current magnitude of `fvec`,</span>
+<a id="ln-207" name="ln-207" href="#ln-207"></a><span class="w">                                                             </span><span class="c">!! * output: new value of `f`</span>
+<a id="ln-208" name="ln-208" href="#ln-208"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec</span><span class="w">   </span><span class="c">!! * input: current function vector,</span>
+<a id="ln-209" name="ln-209" href="#ln-209"></a><span class="w">                                                             </span><span class="c">!! * output: new function vector</span>
+<a id="ln-210" name="ln-210" href="#ln-210"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac</span><span class="w"> </span><span class="c">!! jacobian matrix [dense]</span>
+<a id="ln-211" name="ln-211" href="#ln-211"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac_sparse</span><span class="w"> </span><span class="c">!! jacobian matrix [sparse]</span>
+<a id="ln-212" name="ln-212" href="#ln-212"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">linesearch_func</span>
 <a id="ln-213" name="ln-213" href="#ln-213"></a>
-<a id="ln-214" name="ln-214" href="#ln-214"></a><span class="k">    contains</span>
-<a id="ln-215" name="ln-215" href="#ln-215"></a><span class="c">!*******************************************************************************************************</span>
-<a id="ln-216" name="ln-216" href="#ln-216"></a>
-<a id="ln-217" name="ln-217" href="#ln-217"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-218" name="ln-218" href="#ln-218"></a><span class="c">!&gt;</span>
-<a id="ln-219" name="ln-219" href="#ln-219"></a><span class="c">!  Set status flag and message.</span>
-<a id="ln-220" name="ln-220" href="#ln-220"></a>
-<a id="ln-221" name="ln-221" href="#ln-221"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">set_status</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">istat</span><span class="p">,</span><span class="n">string</span><span class="p">,</span><span class="n">i</span><span class="p">,</span><span class="n">r</span><span class="p">)</span>
+<a id="ln-214" name="ln-214" href="#ln-214"></a><span class="w">    </span><span class="k">end interface</span>
+<a id="ln-215" name="ln-215" href="#ln-215"></a>
+<a id="ln-216" name="ln-216" href="#ln-216"></a><span class="k">    contains</span>
+<a id="ln-217" name="ln-217" href="#ln-217"></a><span class="c">!*******************************************************************************************************</span>
+<a id="ln-218" name="ln-218" href="#ln-218"></a>
+<a id="ln-219" name="ln-219" href="#ln-219"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-220" name="ln-220" href="#ln-220"></a><span class="c">!&gt;</span>
+<a id="ln-221" name="ln-221" href="#ln-221"></a><span class="c">!  Set status flag and message.</span>
 <a id="ln-222" name="ln-222" href="#ln-222"></a>
-<a id="ln-223" name="ln-223" href="#ln-223"></a><span class="w">    </span><span class="k">implicit none</span>
+<a id="ln-223" name="ln-223" href="#ln-223"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">set_status</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">istat</span><span class="p">,</span><span class="n">string</span><span class="p">,</span><span class="n">i</span><span class="p">,</span><span class="n">r</span><span class="p">)</span>
 <a id="ln-224" name="ln-224" href="#ln-224"></a>
-<a id="ln-225" name="ln-225" href="#ln-225"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
-<a id="ln-226" name="ln-226" href="#ln-226"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">                  </span><span class="kd">::</span><span class="w"> </span><span class="n">istat</span><span class="w">   </span><span class="c">!! status code</span>
-<a id="ln-227" name="ln-227" href="#ln-227"></a><span class="w">    </span><span class="kt">character</span><span class="p">(</span><span class="nb">len</span><span class="o">=*</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">         </span><span class="kd">::</span><span class="w"> </span><span class="n">string</span><span class="w">  </span><span class="c">!! status message</span>
-<a id="ln-228" name="ln-228" href="#ln-228"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">         </span><span class="kd">::</span><span class="w"> </span><span class="n">i</span><span class="w">       </span><span class="c">!! an integer value to append</span>
-<a id="ln-229" name="ln-229" href="#ln-229"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">        </span><span class="kd">::</span><span class="w"> </span><span class="n">r</span><span class="w">       </span><span class="c">!! a real value to append</span>
-<a id="ln-230" name="ln-230" href="#ln-230"></a>
-<a id="ln-231" name="ln-231" href="#ln-231"></a><span class="w">    </span><span class="kt">character</span><span class="p">(</span><span class="nb">len</span><span class="o">=</span><span class="mi">256</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">numstr</span><span class="w"> </span><span class="c">!! for number fo string conversion</span>
-<a id="ln-232" name="ln-232" href="#ln-232"></a><span class="w">    </span><span class="kt">character</span><span class="p">(</span><span class="nb">len</span><span class="o">=</span><span class="p">:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">message</span><span class="w"> </span><span class="c">!! the full message to log</span>
-<a id="ln-233" name="ln-233" href="#ln-233"></a><span class="w">    </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">iostat</span><span class="w"> </span><span class="c">!! write `iostat` code</span>
-<a id="ln-234" name="ln-234" href="#ln-234"></a>
-<a id="ln-235" name="ln-235" href="#ln-235"></a><span class="w">    </span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">trim</span><span class="p">(</span><span class="n">string</span><span class="p">)</span>
-<a id="ln-236" name="ln-236" href="#ln-236"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">i</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-237" name="ln-237" href="#ln-237"></a><span class="k">        </span><span class="n">numstr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;&#39;</span>
-<a id="ln-238" name="ln-238" href="#ln-238"></a><span class="w">        </span><span class="k">write</span><span class="p">(</span><span class="n">numstr</span><span class="p">,</span><span class="n">fmt</span><span class="o">=*</span><span class="p">,</span><span class="n">iostat</span><span class="o">=</span><span class="n">iostat</span><span class="p">)</span><span class="w"> </span><span class="n">i</span>
-<a id="ln-239" name="ln-239" href="#ln-239"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">iostat</span><span class="o">/=</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="n">numstr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;****&#39;</span>
-<a id="ln-240" name="ln-240" href="#ln-240"></a><span class="w">        </span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">message</span><span class="o">//</span><span class="s1">&#39; &#39;</span><span class="o">//</span><span class="nb">trim</span><span class="p">(</span><span class="nb">adjustl</span><span class="p">(</span><span class="n">numstr</span><span class="p">))</span>
-<a id="ln-241" name="ln-241" href="#ln-241"></a><span class="w">    </span><span class="k">end if</span>
-<a id="ln-242" name="ln-242" href="#ln-242"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">r</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-243" name="ln-243" href="#ln-243"></a><span class="k">        </span><span class="n">numstr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;&#39;</span>
-<a id="ln-244" name="ln-244" href="#ln-244"></a><span class="w">        </span><span class="k">write</span><span class="p">(</span><span class="n">numstr</span><span class="p">,</span><span class="n">fmt</span><span class="o">=*</span><span class="p">,</span><span class="n">iostat</span><span class="o">=</span><span class="n">iostat</span><span class="p">)</span><span class="w"> </span><span class="n">r</span>
-<a id="ln-245" name="ln-245" href="#ln-245"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">iostat</span><span class="o">/=</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="n">numstr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;****&#39;</span>
-<a id="ln-246" name="ln-246" href="#ln-246"></a><span class="w">        </span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">message</span><span class="o">//</span><span class="s1">&#39; &#39;</span><span class="o">//</span><span class="nb">trim</span><span class="p">(</span><span class="nb">adjustl</span><span class="p">(</span><span class="n">numstr</span><span class="p">))</span>
-<a id="ln-247" name="ln-247" href="#ln-247"></a><span class="w">    </span><span class="k">end if</span>
-<a id="ln-248" name="ln-248" href="#ln-248"></a>
-<a id="ln-249" name="ln-249" href="#ln-249"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">verbose</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-250" name="ln-250" href="#ln-250"></a><span class="k">        write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(A)&#39;</span><span class="p">,</span><span class="n">iostat</span><span class="o">=</span><span class="n">iostat</span><span class="p">)</span><span class="w"> </span><span class="n">message</span>
-<a id="ln-251" name="ln-251" href="#ln-251"></a><span class="w">    </span><span class="k">end if</span>
-<a id="ln-252" name="ln-252" href="#ln-252"></a>
-<a id="ln-253" name="ln-253" href="#ln-253"></a><span class="w">    </span><span class="c">! store in the class:</span>
-<a id="ln-254" name="ln-254" href="#ln-254"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">istat</span>
-<a id="ln-255" name="ln-255" href="#ln-255"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">message</span>
-<a id="ln-256" name="ln-256" href="#ln-256"></a>
-<a id="ln-257" name="ln-257" href="#ln-257"></a><span class="w">    </span><span class="k">end subroutine </span><span class="n">set_status</span>
-<a id="ln-258" name="ln-258" href="#ln-258"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-259" name="ln-259" href="#ln-259"></a>
+<a id="ln-225" name="ln-225" href="#ln-225"></a><span class="w">    </span><span class="k">implicit none</span>
+<a id="ln-226" name="ln-226" href="#ln-226"></a>
+<a id="ln-227" name="ln-227" href="#ln-227"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-228" name="ln-228" href="#ln-228"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">                  </span><span class="kd">::</span><span class="w"> </span><span class="n">istat</span><span class="w">   </span><span class="c">!! status code</span>
+<a id="ln-229" name="ln-229" href="#ln-229"></a><span class="w">    </span><span class="kt">character</span><span class="p">(</span><span class="nb">len</span><span class="o">=*</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">         </span><span class="kd">::</span><span class="w"> </span><span class="n">string</span><span class="w">  </span><span class="c">!! status message</span>
+<a id="ln-230" name="ln-230" href="#ln-230"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">         </span><span class="kd">::</span><span class="w"> </span><span class="n">i</span><span class="w">       </span><span class="c">!! an integer value to append</span>
+<a id="ln-231" name="ln-231" href="#ln-231"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">        </span><span class="kd">::</span><span class="w"> </span><span class="n">r</span><span class="w">       </span><span class="c">!! a real value to append</span>
+<a id="ln-232" name="ln-232" href="#ln-232"></a>
+<a id="ln-233" name="ln-233" href="#ln-233"></a><span class="w">    </span><span class="kt">character</span><span class="p">(</span><span class="nb">len</span><span class="o">=</span><span class="mi">256</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">numstr</span><span class="w"> </span><span class="c">!! for number fo string conversion</span>
+<a id="ln-234" name="ln-234" href="#ln-234"></a><span class="w">    </span><span class="kt">character</span><span class="p">(</span><span class="nb">len</span><span class="o">=</span><span class="p">:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">message</span><span class="w"> </span><span class="c">!! the full message to log</span>
+<a id="ln-235" name="ln-235" href="#ln-235"></a><span class="w">    </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">iostat</span><span class="w"> </span><span class="c">!! write `iostat` code</span>
+<a id="ln-236" name="ln-236" href="#ln-236"></a>
+<a id="ln-237" name="ln-237" href="#ln-237"></a><span class="w">    </span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">trim</span><span class="p">(</span><span class="n">string</span><span class="p">)</span>
+<a id="ln-238" name="ln-238" href="#ln-238"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">i</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-239" name="ln-239" href="#ln-239"></a><span class="k">        </span><span class="n">numstr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;&#39;</span>
+<a id="ln-240" name="ln-240" href="#ln-240"></a><span class="w">        </span><span class="k">write</span><span class="p">(</span><span class="n">numstr</span><span class="p">,</span><span class="n">fmt</span><span class="o">=*</span><span class="p">,</span><span class="n">iostat</span><span class="o">=</span><span class="n">iostat</span><span class="p">)</span><span class="w"> </span><span class="n">i</span>
+<a id="ln-241" name="ln-241" href="#ln-241"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">iostat</span><span class="o">/=</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="n">numstr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;****&#39;</span>
+<a id="ln-242" name="ln-242" href="#ln-242"></a><span class="w">        </span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">message</span><span class="o">//</span><span class="s1">&#39; &#39;</span><span class="o">//</span><span class="nb">trim</span><span class="p">(</span><span class="nb">adjustl</span><span class="p">(</span><span class="n">numstr</span><span class="p">))</span>
+<a id="ln-243" name="ln-243" href="#ln-243"></a><span class="w">    </span><span class="k">end if</span>
+<a id="ln-244" name="ln-244" href="#ln-244"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">r</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-245" name="ln-245" href="#ln-245"></a><span class="k">        </span><span class="n">numstr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;&#39;</span>
+<a id="ln-246" name="ln-246" href="#ln-246"></a><span class="w">        </span><span class="k">write</span><span class="p">(</span><span class="n">numstr</span><span class="p">,</span><span class="n">fmt</span><span class="o">=*</span><span class="p">,</span><span class="n">iostat</span><span class="o">=</span><span class="n">iostat</span><span class="p">)</span><span class="w"> </span><span class="n">r</span>
+<a id="ln-247" name="ln-247" href="#ln-247"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">iostat</span><span class="o">/=</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="n">numstr</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;****&#39;</span>
+<a id="ln-248" name="ln-248" href="#ln-248"></a><span class="w">        </span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">message</span><span class="o">//</span><span class="s1">&#39; &#39;</span><span class="o">//</span><span class="nb">trim</span><span class="p">(</span><span class="nb">adjustl</span><span class="p">(</span><span class="n">numstr</span><span class="p">))</span>
+<a id="ln-249" name="ln-249" href="#ln-249"></a><span class="w">    </span><span class="k">end if</span>
+<a id="ln-250" name="ln-250" href="#ln-250"></a>
+<a id="ln-251" name="ln-251" href="#ln-251"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">verbose</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-252" name="ln-252" href="#ln-252"></a><span class="k">        write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(A)&#39;</span><span class="p">,</span><span class="n">iostat</span><span class="o">=</span><span class="n">iostat</span><span class="p">)</span><span class="w"> </span><span class="n">message</span>
+<a id="ln-253" name="ln-253" href="#ln-253"></a><span class="w">    </span><span class="k">end if</span>
+<a id="ln-254" name="ln-254" href="#ln-254"></a>
+<a id="ln-255" name="ln-255" href="#ln-255"></a><span class="w">    </span><span class="c">! store in the class:</span>
+<a id="ln-256" name="ln-256" href="#ln-256"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">istat</span>
+<a id="ln-257" name="ln-257" href="#ln-257"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">message</span>
+<a id="ln-258" name="ln-258" href="#ln-258"></a>
+<a id="ln-259" name="ln-259" href="#ln-259"></a><span class="w">    </span><span class="k">end subroutine </span><span class="n">set_status</span>
 <a id="ln-260" name="ln-260" href="#ln-260"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-261" name="ln-261" href="#ln-261"></a><span class="c">!&gt;</span>
-<a id="ln-262" name="ln-262" href="#ln-262"></a><span class="c">!  Return the status code and message from the [[nlesolver_type]] class.</span>
-<a id="ln-263" name="ln-263" href="#ln-263"></a><span class="c">!</span>
-<a id="ln-264" name="ln-264" href="#ln-264"></a><span class="c">!### Status codes</span>
+<a id="ln-261" name="ln-261" href="#ln-261"></a>
+<a id="ln-262" name="ln-262" href="#ln-262"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-263" name="ln-263" href="#ln-263"></a><span class="c">!&gt;</span>
+<a id="ln-264" name="ln-264" href="#ln-264"></a><span class="c">!  Return the status code and message from the [[nlesolver_type]] class.</span>
 <a id="ln-265" name="ln-265" href="#ln-265"></a><span class="c">!</span>
-<a id="ln-266" name="ln-266" href="#ln-266"></a><span class="c">!  * -1   -- Error: Invalid alpha</span>
-<a id="ln-267" name="ln-267" href="#ln-267"></a><span class="c">!  * -2   -- Error: Invalid alpha_min</span>
-<a id="ln-268" name="ln-268" href="#ln-268"></a><span class="c">!  * -3   -- Error: Invalid alpha_max</span>
-<a id="ln-269" name="ln-269" href="#ln-269"></a><span class="c">!  * -4   -- Error: Alpha_min must be &lt; alpha_max</span>
-<a id="ln-270" name="ln-270" href="#ln-270"></a><span class="c">!  * -5   -- Error: Invalid step_mode</span>
-<a id="ln-271" name="ln-271" href="#ln-271"></a><span class="c">!  * -6   -- Error solving linear system</span>
-<a id="ln-272" name="ln-272" href="#ln-272"></a><span class="c">!  * -7   -- Error: More than 5 steps in the uphill direction</span>
-<a id="ln-273" name="ln-273" href="#ln-273"></a><span class="c">!  * -8   -- Error: Divide by zero when computing Broyden update</span>
-<a id="ln-274" name="ln-274" href="#ln-274"></a><span class="c">!  * -9   -- Error: Out of memory</span>
-<a id="ln-275" name="ln-275" href="#ln-275"></a><span class="c">!  * -10  -- Error: function routine is not associated</span>
-<a id="ln-276" name="ln-276" href="#ln-276"></a><span class="c">!  * -11  -- Error: gradient routine is not associated</span>
-<a id="ln-277" name="ln-277" href="#ln-277"></a><span class="c">!  * -12  -- Error: backtracking linesearch c must be in range (0, 1)</span>
-<a id="ln-278" name="ln-278" href="#ln-278"></a><span class="c">!  * -13  -- Error: backtracking linesearch tau must be in range (0, 1)</span>
-<a id="ln-279" name="ln-279" href="#ln-279"></a><span class="c">!  * -14  -- Error: must specify grad_sparse, irow, and icol for sparsity_mode &gt; 1</span>
-<a id="ln-280" name="ln-280" href="#ln-280"></a><span class="c">!  * -15  -- Error: irow and icol must be the same length</span>
-<a id="ln-281" name="ln-281" href="#ln-281"></a><span class="c">!  * -999 -- Error: class has not been initialized</span>
-<a id="ln-282" name="ln-282" href="#ln-282"></a><span class="c">!  * 0    -- Class successfully initialized in [[nlesolver_type:initialize]]</span>
-<a id="ln-283" name="ln-283" href="#ln-283"></a><span class="c">!  * 1    -- Required accuracy achieved</span>
-<a id="ln-284" name="ln-284" href="#ln-284"></a><span class="c">!  * 2    -- Solution cannot be improved</span>
-<a id="ln-285" name="ln-285" href="#ln-285"></a><span class="c">!  * 3    -- Maximum number of iterations reached</span>
-<a id="ln-286" name="ln-286" href="#ln-286"></a><span class="c">!  * 4    -- Stopped by the user</span>
-<a id="ln-287" name="ln-287" href="#ln-287"></a>
-<a id="ln-288" name="ln-288" href="#ln-288"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">get_status</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="w"> </span><span class="n">istat</span><span class="p">,</span><span class="w"> </span><span class="n">message</span><span class="p">)</span>
+<a id="ln-266" name="ln-266" href="#ln-266"></a><span class="c">!### Status codes</span>
+<a id="ln-267" name="ln-267" href="#ln-267"></a><span class="c">!</span>
+<a id="ln-268" name="ln-268" href="#ln-268"></a><span class="c">!  * -1   -- Error: Invalid alpha</span>
+<a id="ln-269" name="ln-269" href="#ln-269"></a><span class="c">!  * -2   -- Error: Invalid alpha_min</span>
+<a id="ln-270" name="ln-270" href="#ln-270"></a><span class="c">!  * -3   -- Error: Invalid alpha_max</span>
+<a id="ln-271" name="ln-271" href="#ln-271"></a><span class="c">!  * -4   -- Error: Alpha_min must be &lt; alpha_max</span>
+<a id="ln-272" name="ln-272" href="#ln-272"></a><span class="c">!  * -5   -- Error: Invalid step_mode</span>
+<a id="ln-273" name="ln-273" href="#ln-273"></a><span class="c">!  * -6   -- Error solving linear system</span>
+<a id="ln-274" name="ln-274" href="#ln-274"></a><span class="c">!  * -7   -- Error: More than 5 steps in the uphill direction</span>
+<a id="ln-275" name="ln-275" href="#ln-275"></a><span class="c">!  * -8   -- Error: Divide by zero when computing Broyden update</span>
+<a id="ln-276" name="ln-276" href="#ln-276"></a><span class="c">!  * -9   -- Error: Out of memory</span>
+<a id="ln-277" name="ln-277" href="#ln-277"></a><span class="c">!  * -10  -- Error: function routine is not associated</span>
+<a id="ln-278" name="ln-278" href="#ln-278"></a><span class="c">!  * -11  -- Error: gradient routine is not associated</span>
+<a id="ln-279" name="ln-279" href="#ln-279"></a><span class="c">!  * -12  -- Error: backtracking linesearch c must be in range (0, 1)</span>
+<a id="ln-280" name="ln-280" href="#ln-280"></a><span class="c">!  * -13  -- Error: backtracking linesearch tau must be in range (0, 1)</span>
+<a id="ln-281" name="ln-281" href="#ln-281"></a><span class="c">!  * -14  -- Error: must specify grad_sparse, irow, and icol for sparsity_mode &gt; 1</span>
+<a id="ln-282" name="ln-282" href="#ln-282"></a><span class="c">!  * -15  -- Error: irow and icol must be the same length</span>
+<a id="ln-283" name="ln-283" href="#ln-283"></a><span class="c">!  * -999 -- Error: class has not been initialized</span>
+<a id="ln-284" name="ln-284" href="#ln-284"></a><span class="c">!  * 0    -- Class successfully initialized in [[nlesolver_type:initialize]]</span>
+<a id="ln-285" name="ln-285" href="#ln-285"></a><span class="c">!  * 1    -- Required accuracy achieved</span>
+<a id="ln-286" name="ln-286" href="#ln-286"></a><span class="c">!  * 2    -- Solution cannot be improved</span>
+<a id="ln-287" name="ln-287" href="#ln-287"></a><span class="c">!  * 3    -- Maximum number of iterations reached</span>
+<a id="ln-288" name="ln-288" href="#ln-288"></a><span class="c">!  * 4    -- Stopped by the user</span>
 <a id="ln-289" name="ln-289" href="#ln-289"></a>
-<a id="ln-290" name="ln-290" href="#ln-290"></a><span class="w">    </span><span class="k">implicit none</span>
+<a id="ln-290" name="ln-290" href="#ln-290"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">get_status</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="w"> </span><span class="n">istat</span><span class="p">,</span><span class="w"> </span><span class="n">message</span><span class="p">)</span>
 <a id="ln-291" name="ln-291" href="#ln-291"></a>
-<a id="ln-292" name="ln-292" href="#ln-292"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
-<a id="ln-293" name="ln-293" href="#ln-293"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">istat</span><span class="w">  </span><span class="c">!! Integer status code.</span>
-<a id="ln-294" name="ln-294" href="#ln-294"></a><span class="w">    </span><span class="kt">character</span><span class="p">(</span><span class="nb">len</span><span class="o">=</span><span class="p">:),</span><span class="k">allocatable</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">message</span><span class="w">  </span><span class="c">!! Text status message</span>
-<a id="ln-295" name="ln-295" href="#ln-295"></a>
-<a id="ln-296" name="ln-296" href="#ln-296"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">istat</span><span class="p">))</span><span class="w"> </span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">istat</span>
+<a id="ln-292" name="ln-292" href="#ln-292"></a><span class="w">    </span><span class="k">implicit none</span>
+<a id="ln-293" name="ln-293" href="#ln-293"></a>
+<a id="ln-294" name="ln-294" href="#ln-294"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-295" name="ln-295" href="#ln-295"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">istat</span><span class="w">  </span><span class="c">!! Integer status code.</span>
+<a id="ln-296" name="ln-296" href="#ln-296"></a><span class="w">    </span><span class="kt">character</span><span class="p">(</span><span class="nb">len</span><span class="o">=</span><span class="p">:),</span><span class="k">allocatable</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">message</span><span class="w">  </span><span class="c">!! Text status message</span>
 <a id="ln-297" name="ln-297" href="#ln-297"></a>
-<a id="ln-298" name="ln-298" href="#ln-298"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">message</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-299" name="ln-299" href="#ln-299"></a><span class="k">        if</span><span class="w"> </span><span class="p">(</span><span class="nb">allocated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">message</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-300" name="ln-300" href="#ln-300"></a><span class="k">            </span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">trim</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">message</span><span class="p">)</span>
-<a id="ln-301" name="ln-301" href="#ln-301"></a><span class="w">        </span><span class="k">else</span>
-<a id="ln-302" name="ln-302" href="#ln-302"></a><span class="k">            </span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: class has not been initialized&#39;</span>
-<a id="ln-303" name="ln-303" href="#ln-303"></a><span class="w">        </span><span class="k">end if</span>
-<a id="ln-304" name="ln-304" href="#ln-304"></a><span class="k">    end if</span>
-<a id="ln-305" name="ln-305" href="#ln-305"></a>
-<a id="ln-306" name="ln-306" href="#ln-306"></a><span class="k">    end subroutine </span><span class="n">get_status</span>
-<a id="ln-307" name="ln-307" href="#ln-307"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-308" name="ln-308" href="#ln-308"></a>
+<a id="ln-298" name="ln-298" href="#ln-298"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">istat</span><span class="p">))</span><span class="w"> </span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">istat</span>
+<a id="ln-299" name="ln-299" href="#ln-299"></a>
+<a id="ln-300" name="ln-300" href="#ln-300"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">message</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-301" name="ln-301" href="#ln-301"></a><span class="k">        if</span><span class="w"> </span><span class="p">(</span><span class="nb">allocated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">message</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-302" name="ln-302" href="#ln-302"></a><span class="k">            </span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">trim</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">message</span><span class="p">)</span>
+<a id="ln-303" name="ln-303" href="#ln-303"></a><span class="w">        </span><span class="k">else</span>
+<a id="ln-304" name="ln-304" href="#ln-304"></a><span class="k">            </span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: class has not been initialized&#39;</span>
+<a id="ln-305" name="ln-305" href="#ln-305"></a><span class="w">        </span><span class="k">end if</span>
+<a id="ln-306" name="ln-306" href="#ln-306"></a><span class="k">    end if</span>
+<a id="ln-307" name="ln-307" href="#ln-307"></a>
+<a id="ln-308" name="ln-308" href="#ln-308"></a><span class="k">    end subroutine </span><span class="n">get_status</span>
 <a id="ln-309" name="ln-309" href="#ln-309"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-310" name="ln-310" href="#ln-310"></a><span class="c">!&gt;</span>
-<a id="ln-311" name="ln-311" href="#ln-311"></a><span class="c">!  Constructor for the class.</span>
-<a id="ln-312" name="ln-312" href="#ln-312"></a>
-<a id="ln-313" name="ln-313" href="#ln-313"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">initialize_nlesolver_variables</span><span class="p">(</span><span class="n">me</span><span class="p">,&amp;</span>
-<a id="ln-314" name="ln-314" href="#ln-314"></a><span class="w">                    </span><span class="n">n</span><span class="p">,</span><span class="n">m</span><span class="p">,</span><span class="n">max_iter</span><span class="p">,</span><span class="n">tol</span><span class="p">,</span><span class="n">alpha</span><span class="p">,</span><span class="n">alpha_min</span><span class="p">,</span><span class="n">alpha_max</span><span class="p">,</span><span class="n">tolx</span><span class="p">,</span><span class="n">fmin_tol</span><span class="p">,&amp;</span>
-<a id="ln-315" name="ln-315" href="#ln-315"></a><span class="w">                    </span><span class="n">backtrack_c</span><span class="p">,</span><span class="n">backtrack_tau</span><span class="p">,&amp;</span>
-<a id="ln-316" name="ln-316" href="#ln-316"></a><span class="w">                    </span><span class="n">use_broyden</span><span class="p">,</span><span class="n">broyden_update_n</span><span class="p">,</span><span class="n">step_mode</span><span class="p">,&amp;</span>
-<a id="ln-317" name="ln-317" href="#ln-317"></a><span class="w">                    </span><span class="n">func</span><span class="p">,</span><span class="n">grad</span><span class="p">,</span><span class="n">grad_sparse</span><span class="p">,&amp;</span>
-<a id="ln-318" name="ln-318" href="#ln-318"></a><span class="w">                    </span><span class="n">export_iteration</span><span class="p">,</span><span class="n">user_input_check</span><span class="p">,&amp;</span>
-<a id="ln-319" name="ln-319" href="#ln-319"></a><span class="w">                    </span><span class="n">verbose</span><span class="p">,</span><span class="n">iunit</span><span class="p">,</span><span class="n">n_uphill_max</span><span class="p">,</span><span class="n">n_intervals</span><span class="p">,&amp;</span>
-<a id="ln-320" name="ln-320" href="#ln-320"></a><span class="w">                    </span><span class="n">sparsity_mode</span><span class="p">,</span><span class="n">irow</span><span class="p">,</span><span class="n">icol</span><span class="p">,&amp;</span>
-<a id="ln-321" name="ln-321" href="#ln-321"></a><span class="w">                    </span><span class="n">atol</span><span class="p">,</span><span class="n">btol</span><span class="p">,</span><span class="n">conlim</span><span class="p">,</span><span class="n">damp</span><span class="p">,</span><span class="n">itnlim</span><span class="p">,</span><span class="n">nout</span><span class="p">,&amp;</span>
-<a id="ln-322" name="ln-322" href="#ln-322"></a><span class="w">                    </span><span class="n">lusol_method</span><span class="w"> </span><span class="p">)</span>
-<a id="ln-323" name="ln-323" href="#ln-323"></a>
-<a id="ln-324" name="ln-324" href="#ln-324"></a><span class="w">    </span><span class="k">implicit none</span>
+<a id="ln-310" name="ln-310" href="#ln-310"></a>
+<a id="ln-311" name="ln-311" href="#ln-311"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-312" name="ln-312" href="#ln-312"></a><span class="c">!&gt;</span>
+<a id="ln-313" name="ln-313" href="#ln-313"></a><span class="c">!  Constructor for the class.</span>
+<a id="ln-314" name="ln-314" href="#ln-314"></a>
+<a id="ln-315" name="ln-315" href="#ln-315"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">initialize_nlesolver_variables</span><span class="p">(</span><span class="n">me</span><span class="p">,&amp;</span>
+<a id="ln-316" name="ln-316" href="#ln-316"></a><span class="w">                    </span><span class="n">n</span><span class="p">,</span><span class="n">m</span><span class="p">,</span><span class="n">max_iter</span><span class="p">,</span><span class="n">tol</span><span class="p">,</span><span class="n">alpha</span><span class="p">,</span><span class="n">alpha_min</span><span class="p">,</span><span class="n">alpha_max</span><span class="p">,</span><span class="n">tolx</span><span class="p">,</span><span class="n">fmin_tol</span><span class="p">,&amp;</span>
+<a id="ln-317" name="ln-317" href="#ln-317"></a><span class="w">                    </span><span class="n">backtrack_c</span><span class="p">,</span><span class="n">backtrack_tau</span><span class="p">,&amp;</span>
+<a id="ln-318" name="ln-318" href="#ln-318"></a><span class="w">                    </span><span class="n">use_broyden</span><span class="p">,</span><span class="n">broyden_update_n</span><span class="p">,</span><span class="n">step_mode</span><span class="p">,&amp;</span>
+<a id="ln-319" name="ln-319" href="#ln-319"></a><span class="w">                    </span><span class="n">func</span><span class="p">,</span><span class="n">grad</span><span class="p">,</span><span class="n">grad_sparse</span><span class="p">,&amp;</span>
+<a id="ln-320" name="ln-320" href="#ln-320"></a><span class="w">                    </span><span class="n">export_iteration</span><span class="p">,</span><span class="n">user_input_check</span><span class="p">,&amp;</span>
+<a id="ln-321" name="ln-321" href="#ln-321"></a><span class="w">                    </span><span class="n">verbose</span><span class="p">,</span><span class="n">iunit</span><span class="p">,</span><span class="n">n_uphill_max</span><span class="p">,</span><span class="n">n_intervals</span><span class="p">,&amp;</span>
+<a id="ln-322" name="ln-322" href="#ln-322"></a><span class="w">                    </span><span class="n">sparsity_mode</span><span class="p">,</span><span class="n">irow</span><span class="p">,</span><span class="n">icol</span><span class="p">,&amp;</span>
+<a id="ln-323" name="ln-323" href="#ln-323"></a><span class="w">                    </span><span class="n">atol</span><span class="p">,</span><span class="n">btol</span><span class="p">,</span><span class="n">conlim</span><span class="p">,</span><span class="n">damp</span><span class="p">,</span><span class="n">itnlim</span><span class="p">,</span><span class="n">nout</span><span class="p">,&amp;</span>
+<a id="ln-324" name="ln-324" href="#ln-324"></a><span class="w">                    </span><span class="n">lusol_method</span><span class="w"> </span><span class="p">)</span>
 <a id="ln-325" name="ln-325" href="#ln-325"></a>
-<a id="ln-326" name="ln-326" href="#ln-326"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
-<a id="ln-327" name="ln-327" href="#ln-327"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">                </span><span class="kd">::</span><span class="w"> </span><span class="n">n</span><span class="w">                  </span><span class="c">!! number of optimization variables</span>
-<a id="ln-328" name="ln-328" href="#ln-328"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">                </span><span class="kd">::</span><span class="w"> </span><span class="n">m</span><span class="w">                  </span><span class="c">!! number of constraints</span>
-<a id="ln-329" name="ln-329" href="#ln-329"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">                </span><span class="kd">::</span><span class="w"> </span><span class="n">max_iter</span><span class="w">           </span><span class="c">!! maximum number of iterations</span>
-<a id="ln-330" name="ln-330" href="#ln-330"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">               </span><span class="kd">::</span><span class="w"> </span><span class="n">tol</span><span class="w">                </span><span class="c">!! function convergence tolerance</span>
-<a id="ln-331" name="ln-331" href="#ln-331"></a><span class="w">    </span><span class="k">procedure</span><span class="p">(</span><span class="n">func_func</span><span class="p">)</span><span class="w">              </span><span class="kd">::</span><span class="w"> </span><span class="n">func</span><span class="w">               </span><span class="c">!! computes the function vector</span>
-<a id="ln-332" name="ln-332" href="#ln-332"></a><span class="w">    </span><span class="k">procedure</span><span class="p">(</span><span class="n">grad_func</span><span class="p">),</span><span class="k">optional</span><span class="w">        </span><span class="kd">::</span><span class="w"> </span><span class="n">grad</span><span class="w">            </span><span class="c">!! computes the jacobian [required for dense mode: `sparsity_mode=1`]</span>
-<a id="ln-333" name="ln-333" href="#ln-333"></a><span class="w">    </span><span class="k">procedure</span><span class="p">(</span><span class="n">grad_func_sparse</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">grad_sparse</span><span class="w">     </span><span class="c">!! computes the jacobian [required for sparse mode: `sparsity_mode&gt;1`]</span>
-<a id="ln-334" name="ln-334" href="#ln-334"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">step_mode</span><span class="w">          </span><span class="c">!! step mode:</span>
-<a id="ln-335" name="ln-335" href="#ln-335"></a><span class="w">                                                            </span><span class="c">!!</span>
-<a id="ln-336" name="ln-336" href="#ln-336"></a><span class="w">                                                            </span><span class="c">!!  * 1 = use the specified `alpha` (0,1]</span>
-<a id="ln-337" name="ln-337" href="#ln-337"></a><span class="w">                                                            </span><span class="c">!!  * 2 = backtracking linesearch (between `alpha_min` and `alpha_max`)</span>
-<a id="ln-338" name="ln-338" href="#ln-338"></a><span class="w">                                                            </span><span class="c">!!  * 3 = exact linesearch (between `alpha_min` and `alpha_max`)</span>
-<a id="ln-339" name="ln-339" href="#ln-339"></a><span class="w">                                                            </span><span class="c">!!  * 4 = evaluate function at specified fixed points  (between `alpha_min` and `alpha_max`)</span>
-<a id="ln-340" name="ln-340" href="#ln-340"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">alpha</span><span class="w">              </span><span class="c">!! constant step length for `step_mode=1` (0,1]</span>
-<a id="ln-341" name="ln-341" href="#ln-341"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">alpha_min</span><span class="w">          </span><span class="c">!! minimum step length (0,1]</span>
-<a id="ln-342" name="ln-342" href="#ln-342"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">alpha_max</span><span class="w">          </span><span class="c">!! maximum step length (0,1]</span>
-<a id="ln-343" name="ln-343" href="#ln-343"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">tolx</span><span class="w">               </span><span class="c">!! convergence tolerance for changes in `x`</span>
-<a id="ln-344" name="ln-344" href="#ln-344"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">fmin_tol</span><span class="w">           </span><span class="c">!! convergence tolerance for [[fmin]] (used when `step_mode=3`)</span>
-<a id="ln-345" name="ln-345" href="#ln-345"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">backtrack_c</span><span class="w">        </span><span class="c">!! backtracking linesearch parameter (0,1)</span>
-<a id="ln-346" name="ln-346" href="#ln-346"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">backtrack_tau</span><span class="w">      </span><span class="c">!! backtracking linesearch parameter (0,1)</span>
-<a id="ln-347" name="ln-347" href="#ln-347"></a><span class="w">    </span><span class="kt">logical</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">use_broyden</span><span class="w">        </span><span class="c">!! use a Broyden update (default is False)</span>
-<a id="ln-348" name="ln-348" href="#ln-348"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">broyden_update_n</span><span class="w">   </span><span class="c">!! For Broyden mode, update the full Jacobian</span>
-<a id="ln-349" name="ln-349" href="#ln-349"></a><span class="w">                                                            </span><span class="c">!! at most every this many iterations (must be &gt;1)</span>
-<a id="ln-350" name="ln-350" href="#ln-350"></a><span class="w">                                                            </span><span class="c">!! If &lt;=1 then Jacobian is only computed on the</span>
-<a id="ln-351" name="ln-351" href="#ln-351"></a><span class="w">                                                            </span><span class="c">!! first iteration.</span>
-<a id="ln-352" name="ln-352" href="#ln-352"></a><span class="w">    </span><span class="k">procedure</span><span class="p">(</span><span class="n">export_func</span><span class="p">),</span><span class="k">optional</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">export_iteration</span><span class="w">   </span><span class="c">!! function to export each iteration</span>
-<a id="ln-353" name="ln-353" href="#ln-353"></a><span class="w">    </span><span class="k">procedure</span><span class="p">(</span><span class="n">wait_func</span><span class="p">),</span><span class="k">optional</span><span class="w">     </span><span class="kd">::</span><span class="w"> </span><span class="n">user_input_check</span><span class="w">   </span><span class="c">!! check for user input (to stop solver if necessary)</span>
-<a id="ln-354" name="ln-354" href="#ln-354"></a><span class="w">    </span><span class="kt">logical</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">verbose</span><span class="w">            </span><span class="c">!! for verbose status printing</span>
-<a id="ln-355" name="ln-355" href="#ln-355"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">iunit</span><span class="w">              </span><span class="c">!! unit for verbose printing (assumed to be open).</span>
-<a id="ln-356" name="ln-356" href="#ln-356"></a><span class="w">                                                            </span><span class="c">!! by default this is `output_unit`.</span>
-<a id="ln-357" name="ln-357" href="#ln-357"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">n_uphill_max</span><span class="w">       </span><span class="c">!! maximum number of consecutive steps</span>
-<a id="ln-358" name="ln-358" href="#ln-358"></a><span class="w">                                                            </span><span class="c">!! to allow where the value of `f` increases</span>
-<a id="ln-359" name="ln-359" href="#ln-359"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">n_intervals</span><span class="w">        </span><span class="c">!! number of intervals for fixed point linesearch</span>
-<a id="ln-360" name="ln-360" href="#ln-360"></a>
-<a id="ln-361" name="ln-361" href="#ln-361"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">sparsity_mode</span><span class="w"> </span><span class="c">!! sparsity mode:</span>
-<a id="ln-362" name="ln-362" href="#ln-362"></a><span class="w">                                                 </span><span class="c">!!</span>
-<a id="ln-363" name="ln-363" href="#ln-363"></a><span class="w">                                                 </span><span class="c">!! * 1 - assume dense (use dense solver)</span>
-<a id="ln-364" name="ln-364" href="#ln-364"></a><span class="w">                                                 </span><span class="c">!!   Must specify `grad` for this mode.</span>
-<a id="ln-365" name="ln-365" href="#ln-365"></a><span class="w">                                                 </span><span class="c">!! * 2 - assume sparse (use LSQR sparse solver).</span>
-<a id="ln-366" name="ln-366" href="#ln-366"></a><span class="w">                                                 </span><span class="c">!! * 3 - assume sparse (use LUSOL sparse solver).</span>
-<a id="ln-367" name="ln-367" href="#ln-367"></a><span class="w">                                                 </span><span class="c">!! Must also specify `grad_sparse` and the `irow` and `icol`</span>
-<a id="ln-368" name="ln-368" href="#ln-368"></a><span class="w">                                                 </span><span class="c">!! sparsity pattern for `mode&gt;1`.</span>
-<a id="ln-369" name="ln-369" href="#ln-369"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">irow</span><span class="w"> </span><span class="c">!! sparsity pattern nonzero elements row indices.</span>
-<a id="ln-370" name="ln-370" href="#ln-370"></a><span class="w">                                                     </span><span class="c">!! must be specified with `icol` and be the same length (`n_nonzeros`).</span>
-<a id="ln-371" name="ln-371" href="#ln-371"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">icol</span><span class="w"> </span><span class="c">!! sparsity pattern nonzero elements column indices</span>
+<a id="ln-326" name="ln-326" href="#ln-326"></a><span class="w">    </span><span class="k">implicit none</span>
+<a id="ln-327" name="ln-327" href="#ln-327"></a>
+<a id="ln-328" name="ln-328" href="#ln-328"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-329" name="ln-329" href="#ln-329"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">                </span><span class="kd">::</span><span class="w"> </span><span class="n">n</span><span class="w">                  </span><span class="c">!! number of optimization variables</span>
+<a id="ln-330" name="ln-330" href="#ln-330"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">                </span><span class="kd">::</span><span class="w"> </span><span class="n">m</span><span class="w">                  </span><span class="c">!! number of constraints</span>
+<a id="ln-331" name="ln-331" href="#ln-331"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">                </span><span class="kd">::</span><span class="w"> </span><span class="n">max_iter</span><span class="w">           </span><span class="c">!! maximum number of iterations</span>
+<a id="ln-332" name="ln-332" href="#ln-332"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">               </span><span class="kd">::</span><span class="w"> </span><span class="n">tol</span><span class="w">                </span><span class="c">!! function convergence tolerance</span>
+<a id="ln-333" name="ln-333" href="#ln-333"></a><span class="w">    </span><span class="k">procedure</span><span class="p">(</span><span class="n">func_func</span><span class="p">)</span><span class="w">              </span><span class="kd">::</span><span class="w"> </span><span class="n">func</span><span class="w">               </span><span class="c">!! computes the function vector</span>
+<a id="ln-334" name="ln-334" href="#ln-334"></a><span class="w">    </span><span class="k">procedure</span><span class="p">(</span><span class="n">grad_func</span><span class="p">),</span><span class="k">optional</span><span class="w">        </span><span class="kd">::</span><span class="w"> </span><span class="n">grad</span><span class="w">            </span><span class="c">!! computes the jacobian [required for dense mode: `sparsity_mode=1`]</span>
+<a id="ln-335" name="ln-335" href="#ln-335"></a><span class="w">    </span><span class="k">procedure</span><span class="p">(</span><span class="n">grad_func_sparse</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">grad_sparse</span><span class="w">     </span><span class="c">!! computes the jacobian [required for sparse mode: `sparsity_mode&gt;1`]</span>
+<a id="ln-336" name="ln-336" href="#ln-336"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">step_mode</span><span class="w">          </span><span class="c">!! step mode:</span>
+<a id="ln-337" name="ln-337" href="#ln-337"></a><span class="w">                                                            </span><span class="c">!!</span>
+<a id="ln-338" name="ln-338" href="#ln-338"></a><span class="w">                                                            </span><span class="c">!!  * 1 = use the specified `alpha` (0,1]</span>
+<a id="ln-339" name="ln-339" href="#ln-339"></a><span class="w">                                                            </span><span class="c">!!  * 2 = backtracking linesearch (between `alpha_min` and `alpha_max`)</span>
+<a id="ln-340" name="ln-340" href="#ln-340"></a><span class="w">                                                            </span><span class="c">!!  * 3 = exact linesearch (between `alpha_min` and `alpha_max`)</span>
+<a id="ln-341" name="ln-341" href="#ln-341"></a><span class="w">                                                            </span><span class="c">!!  * 4 = evaluate function at specified fixed points  (between `alpha_min` and `alpha_max`)</span>
+<a id="ln-342" name="ln-342" href="#ln-342"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">alpha</span><span class="w">              </span><span class="c">!! constant step length for `step_mode=1` (0,1]</span>
+<a id="ln-343" name="ln-343" href="#ln-343"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">alpha_min</span><span class="w">          </span><span class="c">!! minimum step length (0,1]</span>
+<a id="ln-344" name="ln-344" href="#ln-344"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">alpha_max</span><span class="w">          </span><span class="c">!! maximum step length (0,1]</span>
+<a id="ln-345" name="ln-345" href="#ln-345"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">tolx</span><span class="w">               </span><span class="c">!! convergence tolerance for changes in `x`</span>
+<a id="ln-346" name="ln-346" href="#ln-346"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">fmin_tol</span><span class="w">           </span><span class="c">!! convergence tolerance for [[fmin]] (used when `step_mode=3`)</span>
+<a id="ln-347" name="ln-347" href="#ln-347"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">backtrack_c</span><span class="w">        </span><span class="c">!! backtracking linesearch parameter (0,1)</span>
+<a id="ln-348" name="ln-348" href="#ln-348"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">backtrack_tau</span><span class="w">      </span><span class="c">!! backtracking linesearch parameter (0,1)</span>
+<a id="ln-349" name="ln-349" href="#ln-349"></a><span class="w">    </span><span class="kt">logical</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">use_broyden</span><span class="w">        </span><span class="c">!! use a Broyden update (default is False)</span>
+<a id="ln-350" name="ln-350" href="#ln-350"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">broyden_update_n</span><span class="w">   </span><span class="c">!! For Broyden mode, update the full Jacobian</span>
+<a id="ln-351" name="ln-351" href="#ln-351"></a><span class="w">                                                            </span><span class="c">!! at most every this many iterations (must be &gt;1)</span>
+<a id="ln-352" name="ln-352" href="#ln-352"></a><span class="w">                                                            </span><span class="c">!! If &lt;=1 then Jacobian is only computed on the</span>
+<a id="ln-353" name="ln-353" href="#ln-353"></a><span class="w">                                                            </span><span class="c">!! first iteration.</span>
+<a id="ln-354" name="ln-354" href="#ln-354"></a><span class="w">    </span><span class="k">procedure</span><span class="p">(</span><span class="n">export_func</span><span class="p">),</span><span class="k">optional</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">export_iteration</span><span class="w">   </span><span class="c">!! function to export each iteration</span>
+<a id="ln-355" name="ln-355" href="#ln-355"></a><span class="w">    </span><span class="k">procedure</span><span class="p">(</span><span class="n">wait_func</span><span class="p">),</span><span class="k">optional</span><span class="w">     </span><span class="kd">::</span><span class="w"> </span><span class="n">user_input_check</span><span class="w">   </span><span class="c">!! check for user input (to stop solver if necessary)</span>
+<a id="ln-356" name="ln-356" href="#ln-356"></a><span class="w">    </span><span class="kt">logical</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">verbose</span><span class="w">            </span><span class="c">!! for verbose status printing</span>
+<a id="ln-357" name="ln-357" href="#ln-357"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">iunit</span><span class="w">              </span><span class="c">!! unit for verbose printing (assumed to be open).</span>
+<a id="ln-358" name="ln-358" href="#ln-358"></a><span class="w">                                                            </span><span class="c">!! by default this is `output_unit`.</span>
+<a id="ln-359" name="ln-359" href="#ln-359"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">n_uphill_max</span><span class="w">       </span><span class="c">!! maximum number of consecutive steps</span>
+<a id="ln-360" name="ln-360" href="#ln-360"></a><span class="w">                                                            </span><span class="c">!! to allow where the value of `f` increases</span>
+<a id="ln-361" name="ln-361" href="#ln-361"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">n_intervals</span><span class="w">        </span><span class="c">!! number of intervals for fixed point linesearch</span>
+<a id="ln-362" name="ln-362" href="#ln-362"></a>
+<a id="ln-363" name="ln-363" href="#ln-363"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">sparsity_mode</span><span class="w"> </span><span class="c">!! sparsity mode:</span>
+<a id="ln-364" name="ln-364" href="#ln-364"></a><span class="w">                                                 </span><span class="c">!!</span>
+<a id="ln-365" name="ln-365" href="#ln-365"></a><span class="w">                                                 </span><span class="c">!! * 1 - assume dense (use dense solver)</span>
+<a id="ln-366" name="ln-366" href="#ln-366"></a><span class="w">                                                 </span><span class="c">!!   Must specify `grad` for this mode.</span>
+<a id="ln-367" name="ln-367" href="#ln-367"></a><span class="w">                                                 </span><span class="c">!! * 2 - assume sparse (use LSQR sparse solver).</span>
+<a id="ln-368" name="ln-368" href="#ln-368"></a><span class="w">                                                 </span><span class="c">!! * 3 - assume sparse (use LUSOL sparse solver).</span>
+<a id="ln-369" name="ln-369" href="#ln-369"></a><span class="w">                                                 </span><span class="c">!! Must also specify `grad_sparse` and the `irow` and `icol`</span>
+<a id="ln-370" name="ln-370" href="#ln-370"></a><span class="w">                                                 </span><span class="c">!! sparsity pattern for `mode&gt;1`.</span>
+<a id="ln-371" name="ln-371" href="#ln-371"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">irow</span><span class="w"> </span><span class="c">!! sparsity pattern nonzero elements row indices.</span>
 <a id="ln-372" name="ln-372" href="#ln-372"></a><span class="w">                                                     </span><span class="c">!! must be specified with `icol` and be the same length (`n_nonzeros`).</span>
-<a id="ln-373" name="ln-373" href="#ln-373"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">atol</span><span class="w">    </span><span class="c">!! `LSQR`: relative error in definition of `A`</span>
-<a id="ln-374" name="ln-374" href="#ln-374"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">btol</span><span class="w">    </span><span class="c">!! `LSQR`: relative error in definition of `b`</span>
-<a id="ln-375" name="ln-375" href="#ln-375"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">conlim</span><span class="w">  </span><span class="c">!! `LSQR`: An upper limit on `cond(Abar)`, the apparent</span>
-<a id="ln-376" name="ln-376" href="#ln-376"></a><span class="w">                                                 </span><span class="c">!! condition number of the matrix `Abar`.</span>
-<a id="ln-377" name="ln-377" href="#ln-377"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">damp</span><span class="w">    </span><span class="c">!! `LSQR`: damp factor</span>
-<a id="ln-378" name="ln-378" href="#ln-378"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">itnlim</span><span class="w">  </span><span class="c">!! `LSQR`: max iterations</span>
-<a id="ln-379" name="ln-379" href="#ln-379"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">nout</span><span class="w">    </span><span class="c">!! `LSQR`: output unit for printing</span>
-<a id="ln-380" name="ln-380" href="#ln-380"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">lusol_method</span>
-<a id="ln-381" name="ln-381" href="#ln-381"></a>
-<a id="ln-382" name="ln-382" href="#ln-382"></a><span class="w">    </span><span class="kt">logical</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">status_ok</span><span class="w"> </span><span class="c">!! true if there were no errors</span>
-<a id="ln-383" name="ln-383" href="#ln-383"></a>
-<a id="ln-384" name="ln-384" href="#ln-384"></a><span class="w">    </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">true</span><span class="p">.</span>
-<a id="ln-385" name="ln-385" href="#ln-385"></a>
-<a id="ln-386" name="ln-386" href="#ln-386"></a><span class="w">    </span><span class="c">!required:</span>
-<a id="ln-387" name="ln-387" href="#ln-387"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="w">        </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>
-<a id="ln-388" name="ln-388" href="#ln-388"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="w">        </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">m</span><span class="p">)</span>
-<a id="ln-389" name="ln-389" href="#ln-389"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">max_iter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">max_iter</span><span class="p">)</span>
-<a id="ln-390" name="ln-390" href="#ln-390"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">tol</span><span class="w">      </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">tol</span><span class="p">)</span>
-<a id="ln-391" name="ln-391" href="#ln-391"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="w">     </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">func</span>
-<a id="ln-392" name="ln-392" href="#ln-392"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">grad</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">grad</span><span class="w">               </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">grad</span>
-<a id="ln-393" name="ln-393" href="#ln-393"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">grad_sparse</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">grad_sparse</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">grad_sparse</span>
-<a id="ln-394" name="ln-394" href="#ln-394"></a>
-<a id="ln-395" name="ln-395" href="#ln-395"></a><span class="w">    </span><span class="c">!optional:</span>
-<a id="ln-396" name="ln-396" href="#ln-396"></a>
-<a id="ln-397" name="ln-397" href="#ln-397"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">step_mode</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-398" name="ln-398" href="#ln-398"></a><span class="k">        select case</span><span class="w"> </span><span class="p">(</span><span class="n">step_mode</span><span class="p">)</span>
-<a id="ln-399" name="ln-399" href="#ln-399"></a><span class="w">        </span><span class="k">case</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="c">! = use the specified `alpha` (0,1]</span>
-<a id="ln-400" name="ln-400" href="#ln-400"></a><span class="w">            </span><span class="n">me</span><span class="p">%</span><span class="n">linesearch</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">simple_step</span>
-<a id="ln-401" name="ln-401" href="#ln-401"></a><span class="w">        </span><span class="k">case</span><span class="p">(</span><span class="mi">2</span><span class="p">)</span><span class="w"> </span><span class="c">! = backtracking linesearch (between `alpha_min` and `alpha_max`)</span>
-<a id="ln-402" name="ln-402" href="#ln-402"></a><span class="w">            </span><span class="n">me</span><span class="p">%</span><span class="n">linesearch</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">backtracking_linesearch</span>
-<a id="ln-403" name="ln-403" href="#ln-403"></a><span class="w">        </span><span class="k">case</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span><span class="w"> </span><span class="c">! = exact linesearch (between `alpha_min` and `alpha_max`)</span>
-<a id="ln-404" name="ln-404" href="#ln-404"></a><span class="w">            </span><span class="n">me</span><span class="p">%</span><span class="n">linesearch</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">exact_linesearch</span>
-<a id="ln-405" name="ln-405" href="#ln-405"></a><span class="w">        </span><span class="k">case</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span><span class="w"> </span><span class="c">! = evaluate function at specified fixed points (between `alpha_min` and `alpha_max`)</span>
-<a id="ln-406" name="ln-406" href="#ln-406"></a><span class="w">            </span><span class="n">me</span><span class="p">%</span><span class="n">linesearch</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">fixed_point_linesearch</span>
-<a id="ln-407" name="ln-407" href="#ln-407"></a><span class="w">        </span><span class="k">case </span><span class="n">default</span>
-<a id="ln-408" name="ln-408" href="#ln-408"></a><span class="w">            </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
-<a id="ln-409" name="ln-409" href="#ln-409"></a><span class="w">            </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: invalid step_mode:&#39;</span><span class="p">,</span><span class="n">i</span><span class="o">=</span><span class="n">step_mode</span><span class="p">)</span>
-<a id="ln-410" name="ln-410" href="#ln-410"></a><span class="w">            </span><span class="k">return</span>
-<a id="ln-411" name="ln-411" href="#ln-411"></a><span class="k">        end select</span>
-<a id="ln-412" name="ln-412" href="#ln-412"></a><span class="k">    else</span>
-<a id="ln-413" name="ln-413" href="#ln-413"></a><span class="k">        </span><span class="n">me</span><span class="p">%</span><span class="n">linesearch</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">simple_step</span>
-<a id="ln-414" name="ln-414" href="#ln-414"></a><span class="w">    </span><span class="k">end if</span>
-<a id="ln-415" name="ln-415" href="#ln-415"></a>
-<a id="ln-416" name="ln-416" href="#ln-416"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">alpha</span><span class="p">))</span><span class="w">             </span><span class="n">me</span><span class="p">%</span><span class="n">alpha</span><span class="w">             </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">alpha</span><span class="p">)</span>
-<a id="ln-417" name="ln-417" href="#ln-417"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">alpha_min</span><span class="p">))</span><span class="w">         </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="w">         </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">alpha_min</span><span class="p">)</span>
-<a id="ln-418" name="ln-418" href="#ln-418"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">alpha_max</span><span class="p">))</span><span class="w">         </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="w">         </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">alpha_max</span><span class="p">)</span>
-<a id="ln-419" name="ln-419" href="#ln-419"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">tolx</span><span class="p">))</span><span class="w">              </span><span class="n">me</span><span class="p">%</span><span class="n">tolx</span><span class="w">              </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">tolx</span><span class="p">)</span>
-<a id="ln-420" name="ln-420" href="#ln-420"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">backtrack_c</span><span class="p">))</span><span class="w">       </span><span class="n">me</span><span class="p">%</span><span class="n">c</span><span class="w">                 </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">backtrack_c</span><span class="p">)</span>
-<a id="ln-421" name="ln-421" href="#ln-421"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">backtrack_tau</span><span class="p">))</span><span class="w">     </span><span class="n">me</span><span class="p">%</span><span class="n">tau</span><span class="w">               </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">backtrack_tau</span><span class="p">)</span>
-<a id="ln-422" name="ln-422" href="#ln-422"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">use_broyden</span><span class="p">))</span><span class="w">       </span><span class="n">me</span><span class="p">%</span><span class="n">use_broyden</span><span class="w">       </span><span class="o">=</span><span class="w"> </span><span class="n">use_broyden</span>
-<a id="ln-423" name="ln-423" href="#ln-423"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">broyden_update_n</span><span class="p">))</span><span class="w">  </span><span class="n">me</span><span class="p">%</span><span class="n">broyden_update_n</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">broyden_update_n</span><span class="p">)</span>
-<a id="ln-424" name="ln-424" href="#ln-424"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">verbose</span><span class="p">))</span><span class="w">           </span><span class="n">me</span><span class="p">%</span><span class="n">verbose</span><span class="w">           </span><span class="o">=</span><span class="w"> </span><span class="n">verbose</span>
-<a id="ln-425" name="ln-425" href="#ln-425"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">iunit</span><span class="p">))</span><span class="w">             </span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="w">             </span><span class="o">=</span><span class="w"> </span><span class="n">iunit</span>
-<a id="ln-426" name="ln-426" href="#ln-426"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">n_uphill_max</span><span class="p">))</span><span class="w">      </span><span class="n">me</span><span class="p">%</span><span class="n">n_uphill_max</span><span class="w">      </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">n_uphill_max</span><span class="p">)</span>
-<a id="ln-427" name="ln-427" href="#ln-427"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">n_intervals</span><span class="p">))</span><span class="w">       </span><span class="n">me</span><span class="p">%</span><span class="n">n_intervals</span><span class="w">       </span><span class="o">=</span><span class="w"> </span><span class="nb">max</span><span class="p">(</span><span class="nb">abs</span><span class="p">(</span><span class="n">n_intervals</span><span class="p">),</span><span class="mi">1</span><span class="p">)</span>
-<a id="ln-428" name="ln-428" href="#ln-428"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">fmin_tol</span><span class="p">))</span><span class="w">          </span><span class="n">me</span><span class="p">%</span><span class="n">fmin_tol</span><span class="w">          </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">fmin_tol</span><span class="p">)</span>
-<a id="ln-429" name="ln-429" href="#ln-429"></a>
-<a id="ln-430" name="ln-430" href="#ln-430"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">export_iteration</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">export_iteration</span><span class="w">  </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">export_iteration</span>
-<a id="ln-431" name="ln-431" href="#ln-431"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">user_input_check</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">user_input_check</span><span class="w">  </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">user_input_check</span>
-<a id="ln-432" name="ln-432" href="#ln-432"></a>
-<a id="ln-433" name="ln-433" href="#ln-433"></a><span class="w">    </span><span class="c">! error checks:</span>
-<a id="ln-434" name="ln-434" href="#ln-434"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">alpha</span><span class="o">&lt;</span><span class="n">zero</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha</span><span class="o">&gt;</span><span class="n">one</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-435" name="ln-435" href="#ln-435"></a><span class="k">        </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
-<a id="ln-436" name="ln-436" href="#ln-436"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: invalid alpha:&#39;</span><span class="p">,</span><span class="n">r</span><span class="o">=</span><span class="n">me</span><span class="p">%</span><span class="n">alpha</span><span class="p">)</span>
-<a id="ln-437" name="ln-437" href="#ln-437"></a><span class="w">        </span><span class="k">return</span>
-<a id="ln-438" name="ln-438" href="#ln-438"></a><span class="k">    end if</span>
-<a id="ln-439" name="ln-439" href="#ln-439"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="o">&lt;</span><span class="n">zero</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="o">&gt;</span><span class="n">one</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-440" name="ln-440" href="#ln-440"></a><span class="k">        </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
-<a id="ln-441" name="ln-441" href="#ln-441"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: invalid alpha_min:&#39;</span><span class="p">,</span><span class="n">r</span><span class="o">=</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="p">)</span>
-<a id="ln-442" name="ln-442" href="#ln-442"></a><span class="w">        </span><span class="k">return</span>
-<a id="ln-443" name="ln-443" href="#ln-443"></a><span class="k">    end if</span>
-<a id="ln-444" name="ln-444" href="#ln-444"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="o">&lt;</span><span class="n">zero</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="o">&gt;</span><span class="n">one</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-445" name="ln-445" href="#ln-445"></a><span class="k">        </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
-<a id="ln-446" name="ln-446" href="#ln-446"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: invalid alpha_max:&#39;</span><span class="p">,</span><span class="n">r</span><span class="o">=</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="p">)</span>
-<a id="ln-447" name="ln-447" href="#ln-447"></a><span class="w">        </span><span class="k">return</span>
-<a id="ln-448" name="ln-448" href="#ln-448"></a><span class="k">    end if</span>
-<a id="ln-449" name="ln-449" href="#ln-449"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="o">&lt;=</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-450" name="ln-450" href="#ln-450"></a><span class="k">        </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
-<a id="ln-451" name="ln-451" href="#ln-451"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: alpha_min must be &lt; alpha_max&#39;</span><span class="p">)</span>
-<a id="ln-452" name="ln-452" href="#ln-452"></a><span class="w">        </span><span class="k">return</span>
-<a id="ln-453" name="ln-453" href="#ln-453"></a><span class="k">    end if</span>
-<a id="ln-454" name="ln-454" href="#ln-454"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">c</span><span class="o">&lt;</span><span class="n">zero</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">c</span><span class="o">&gt;</span><span class="n">one</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-455" name="ln-455" href="#ln-455"></a><span class="k">        </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
-<a id="ln-456" name="ln-456" href="#ln-456"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">12</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: backtracking linesearch c must be in range (0, 1):&#39;</span><span class="p">,</span><span class="n">r</span><span class="o">=</span><span class="n">me</span><span class="p">%</span><span class="n">c</span><span class="p">)</span>
-<a id="ln-457" name="ln-457" href="#ln-457"></a><span class="w">        </span><span class="k">return</span>
-<a id="ln-458" name="ln-458" href="#ln-458"></a><span class="k">    end if</span>
-<a id="ln-459" name="ln-459" href="#ln-459"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">tau</span><span class="o">&lt;</span><span class="n">zero</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">tau</span><span class="o">&gt;</span><span class="n">one</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-460" name="ln-460" href="#ln-460"></a><span class="k">        </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
-<a id="ln-461" name="ln-461" href="#ln-461"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">13</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: backtracking linesearch tau must be in range (0, 1):&#39;</span><span class="p">,</span><span class="n">r</span><span class="o">=</span><span class="n">me</span><span class="p">%</span><span class="n">tau</span><span class="p">)</span>
-<a id="ln-462" name="ln-462" href="#ln-462"></a><span class="w">        </span><span class="k">return</span>
-<a id="ln-463" name="ln-463" href="#ln-463"></a><span class="k">    end if</span>
-<a id="ln-464" name="ln-464" href="#ln-464"></a>
-<a id="ln-465" name="ln-465" href="#ln-465"></a><span class="w">    </span><span class="c">! initialize:</span>
-<a id="ln-466" name="ln-466" href="#ln-466"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">n_nonzeros</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">1</span><span class="w"> </span><span class="c">! not used</span>
-<a id="ln-467" name="ln-467" href="#ln-467"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">allocated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">irow</span><span class="p">))</span><span class="w"> </span><span class="k">deallocate</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">irow</span><span class="p">)</span>
-<a id="ln-468" name="ln-468" href="#ln-468"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">allocated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="p">))</span><span class="w"> </span><span class="k">deallocate</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="p">)</span>
-<a id="ln-469" name="ln-469" href="#ln-469"></a>
-<a id="ln-470" name="ln-470" href="#ln-470"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">sparsity_mode</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-471" name="ln-471" href="#ln-471"></a><span class="k">        </span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sparsity_mode</span>
-<a id="ln-472" name="ln-472" href="#ln-472"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">sparsity_mode</span><span class="o">&gt;</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="k">then</span><span class="w"> </span><span class="c">! sparse solver method</span>
-<a id="ln-473" name="ln-473" href="#ln-473"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">irow</span><span class="p">)</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="nb">present</span><span class="p">(</span><span class="n">icol</span><span class="p">)</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="nb">present</span><span class="p">(</span><span class="n">grad_sparse</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-474" name="ln-474" href="#ln-474"></a><span class="k">                if</span><span class="w"> </span><span class="p">(</span><span class="n">size</span><span class="p">(</span><span class="n">irow</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">size</span><span class="p">(</span><span class="n">icol</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-475" name="ln-475" href="#ln-475"></a><span class="k">                    </span><span class="n">me</span><span class="p">%</span><span class="n">n_nonzeros</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">size</span><span class="p">(</span><span class="n">irow</span><span class="p">)</span>
-<a id="ln-476" name="ln-476" href="#ln-476"></a><span class="w">                    </span><span class="n">me</span><span class="p">%</span><span class="n">irow</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">irow</span>
-<a id="ln-477" name="ln-477" href="#ln-477"></a><span class="w">                    </span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">icol</span>
-<a id="ln-478" name="ln-478" href="#ln-478"></a><span class="w">                </span><span class="k">else</span>
-<a id="ln-479" name="ln-479" href="#ln-479"></a><span class="k">                    call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">15</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: irow and icol must be the same length&#39;</span><span class="p">)</span>
-<a id="ln-480" name="ln-480" href="#ln-480"></a><span class="w">                    </span><span class="k">return</span>
-<a id="ln-481" name="ln-481" href="#ln-481"></a><span class="k">                end if</span>
-<a id="ln-482" name="ln-482" href="#ln-482"></a><span class="k">            else</span>
-<a id="ln-483" name="ln-483" href="#ln-483"></a><span class="k">                call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">14</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: must specify grad_sparse, irow, and icol for sparsity_mode &gt; 1&#39;</span><span class="p">)</span>
-<a id="ln-484" name="ln-484" href="#ln-484"></a><span class="w">                </span><span class="k">return</span>
-<a id="ln-485" name="ln-485" href="#ln-485"></a><span class="k">            end if</span>
-<a id="ln-486" name="ln-486" href="#ln-486"></a><span class="w">            </span><span class="c">! LSQR optional inputs:</span>
-<a id="ln-487" name="ln-487" href="#ln-487"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">atol</span><span class="p">))</span><span class="w">   </span><span class="n">me</span><span class="p">%</span><span class="n">atol</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="n">atol</span>
-<a id="ln-488" name="ln-488" href="#ln-488"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">btol</span><span class="p">))</span><span class="w">   </span><span class="n">me</span><span class="p">%</span><span class="n">btol</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="n">btol</span>
-<a id="ln-489" name="ln-489" href="#ln-489"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">conlim</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">conlim</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">conlim</span>
-<a id="ln-490" name="ln-490" href="#ln-490"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">damp</span><span class="p">))</span><span class="w">   </span><span class="n">me</span><span class="p">%</span><span class="n">damp</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="n">damp</span>
-<a id="ln-491" name="ln-491" href="#ln-491"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">itnlim</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">itnlim</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">itnlim</span>
-<a id="ln-492" name="ln-492" href="#ln-492"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">nout</span><span class="p">))</span><span class="w">   </span><span class="n">me</span><span class="p">%</span><span class="n">nout</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="n">nout</span>
-<a id="ln-493" name="ln-493" href="#ln-493"></a>
-<a id="ln-494" name="ln-494" href="#ln-494"></a><span class="w">            </span><span class="c">! LUSOL method</span>
-<a id="ln-495" name="ln-495" href="#ln-495"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">nout</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">lusol_method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lusol_method</span>
-<a id="ln-496" name="ln-496" href="#ln-496"></a>
-<a id="ln-497" name="ln-497" href="#ln-497"></a><span class="w">            </span><span class="c">! now now, some options are not available for sparse mode</span>
-<a id="ln-498" name="ln-498" href="#ln-498"></a><span class="w">            </span><span class="c">!...see if this is possible in sparse mode... TODO</span>
-<a id="ln-499" name="ln-499" href="#ln-499"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">use_broyden</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-500" name="ln-500" href="#ln-500"></a><span class="k">                call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">16</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: broyden method not available for sparse solver&#39;</span><span class="p">)</span>
-<a id="ln-501" name="ln-501" href="#ln-501"></a><span class="w">                </span><span class="k">return</span>
-<a id="ln-502" name="ln-502" href="#ln-502"></a><span class="k">            end if</span>
-<a id="ln-503" name="ln-503" href="#ln-503"></a><span class="k">        end if</span>
+<a id="ln-373" name="ln-373" href="#ln-373"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">icol</span><span class="w"> </span><span class="c">!! sparsity pattern nonzero elements column indices</span>
+<a id="ln-374" name="ln-374" href="#ln-374"></a><span class="w">                                                     </span><span class="c">!! must be specified with `icol` and be the same length (`n_nonzeros`).</span>
+<a id="ln-375" name="ln-375" href="#ln-375"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">atol</span><span class="w">    </span><span class="c">!! `LSQR`: relative error in definition of `A`</span>
+<a id="ln-376" name="ln-376" href="#ln-376"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">btol</span><span class="w">    </span><span class="c">!! `LSQR`: relative error in definition of `b`</span>
+<a id="ln-377" name="ln-377" href="#ln-377"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">conlim</span><span class="w">  </span><span class="c">!! `LSQR`: An upper limit on `cond(Abar)`, the apparent</span>
+<a id="ln-378" name="ln-378" href="#ln-378"></a><span class="w">                                                 </span><span class="c">!! condition number of the matrix `Abar`.</span>
+<a id="ln-379" name="ln-379" href="#ln-379"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">      </span><span class="kd">::</span><span class="w"> </span><span class="n">damp</span><span class="w">    </span><span class="c">!! `LSQR`: damp factor</span>
+<a id="ln-380" name="ln-380" href="#ln-380"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">itnlim</span><span class="w">  </span><span class="c">!! `LSQR`: max iterations</span>
+<a id="ln-381" name="ln-381" href="#ln-381"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">nout</span><span class="w">    </span><span class="c">!! `LSQR`: output unit for printing</span>
+<a id="ln-382" name="ln-382" href="#ln-382"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w">       </span><span class="kd">::</span><span class="w"> </span><span class="n">lusol_method</span><span class="w"> </span><span class="c">!! `LUSOL` method:</span>
+<a id="ln-383" name="ln-383" href="#ln-383"></a><span class="w">                                                      </span><span class="c">!!</span>
+<a id="ln-384" name="ln-384" href="#ln-384"></a><span class="w">                                                      </span><span class="c">!! * 0 =&gt; TPP: Threshold Partial   Pivoting.</span>
+<a id="ln-385" name="ln-385" href="#ln-385"></a><span class="w">                                                      </span><span class="c">!! * 1 =&gt; TRP: Threshold Rook      Pivoting.</span>
+<a id="ln-386" name="ln-386" href="#ln-386"></a><span class="w">                                                      </span><span class="c">!! * 2 =&gt; TCP: Threshold Complete  Pivoting.</span>
+<a id="ln-387" name="ln-387" href="#ln-387"></a>
+<a id="ln-388" name="ln-388" href="#ln-388"></a><span class="w">    </span><span class="kt">logical</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">status_ok</span><span class="w"> </span><span class="c">!! true if there were no errors</span>
+<a id="ln-389" name="ln-389" href="#ln-389"></a>
+<a id="ln-390" name="ln-390" href="#ln-390"></a><span class="w">    </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">true</span><span class="p">.</span>
+<a id="ln-391" name="ln-391" href="#ln-391"></a>
+<a id="ln-392" name="ln-392" href="#ln-392"></a><span class="w">    </span><span class="c">!required:</span>
+<a id="ln-393" name="ln-393" href="#ln-393"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="w">        </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>
+<a id="ln-394" name="ln-394" href="#ln-394"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="w">        </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">m</span><span class="p">)</span>
+<a id="ln-395" name="ln-395" href="#ln-395"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">max_iter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">max_iter</span><span class="p">)</span>
+<a id="ln-396" name="ln-396" href="#ln-396"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">tol</span><span class="w">      </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">tol</span><span class="p">)</span>
+<a id="ln-397" name="ln-397" href="#ln-397"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="w">     </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">func</span>
+<a id="ln-398" name="ln-398" href="#ln-398"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">grad</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">grad</span><span class="w">               </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">grad</span>
+<a id="ln-399" name="ln-399" href="#ln-399"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">grad_sparse</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">grad_sparse</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">grad_sparse</span>
+<a id="ln-400" name="ln-400" href="#ln-400"></a>
+<a id="ln-401" name="ln-401" href="#ln-401"></a><span class="w">    </span><span class="c">!optional:</span>
+<a id="ln-402" name="ln-402" href="#ln-402"></a>
+<a id="ln-403" name="ln-403" href="#ln-403"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">step_mode</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-404" name="ln-404" href="#ln-404"></a><span class="k">        select case</span><span class="w"> </span><span class="p">(</span><span class="n">step_mode</span><span class="p">)</span>
+<a id="ln-405" name="ln-405" href="#ln-405"></a><span class="w">        </span><span class="k">case</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="c">! = use the specified `alpha` (0,1]</span>
+<a id="ln-406" name="ln-406" href="#ln-406"></a><span class="w">            </span><span class="n">me</span><span class="p">%</span><span class="n">linesearch</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">simple_step</span>
+<a id="ln-407" name="ln-407" href="#ln-407"></a><span class="w">        </span><span class="k">case</span><span class="p">(</span><span class="mi">2</span><span class="p">)</span><span class="w"> </span><span class="c">! = backtracking linesearch (between `alpha_min` and `alpha_max`)</span>
+<a id="ln-408" name="ln-408" href="#ln-408"></a><span class="w">            </span><span class="n">me</span><span class="p">%</span><span class="n">linesearch</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">backtracking_linesearch</span>
+<a id="ln-409" name="ln-409" href="#ln-409"></a><span class="w">        </span><span class="k">case</span><span class="p">(</span><span class="mi">3</span><span class="p">)</span><span class="w"> </span><span class="c">! = exact linesearch (between `alpha_min` and `alpha_max`)</span>
+<a id="ln-410" name="ln-410" href="#ln-410"></a><span class="w">            </span><span class="n">me</span><span class="p">%</span><span class="n">linesearch</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">exact_linesearch</span>
+<a id="ln-411" name="ln-411" href="#ln-411"></a><span class="w">        </span><span class="k">case</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span><span class="w"> </span><span class="c">! = evaluate function at specified fixed points (between `alpha_min` and `alpha_max`)</span>
+<a id="ln-412" name="ln-412" href="#ln-412"></a><span class="w">            </span><span class="n">me</span><span class="p">%</span><span class="n">linesearch</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">fixed_point_linesearch</span>
+<a id="ln-413" name="ln-413" href="#ln-413"></a><span class="w">        </span><span class="k">case </span><span class="n">default</span>
+<a id="ln-414" name="ln-414" href="#ln-414"></a><span class="w">            </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
+<a id="ln-415" name="ln-415" href="#ln-415"></a><span class="w">            </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: invalid step_mode:&#39;</span><span class="p">,</span><span class="n">i</span><span class="o">=</span><span class="n">step_mode</span><span class="p">)</span>
+<a id="ln-416" name="ln-416" href="#ln-416"></a><span class="w">            </span><span class="k">return</span>
+<a id="ln-417" name="ln-417" href="#ln-417"></a><span class="k">        end select</span>
+<a id="ln-418" name="ln-418" href="#ln-418"></a><span class="k">    else</span>
+<a id="ln-419" name="ln-419" href="#ln-419"></a><span class="k">        </span><span class="n">me</span><span class="p">%</span><span class="n">linesearch</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">simple_step</span>
+<a id="ln-420" name="ln-420" href="#ln-420"></a><span class="w">    </span><span class="k">end if</span>
+<a id="ln-421" name="ln-421" href="#ln-421"></a>
+<a id="ln-422" name="ln-422" href="#ln-422"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">alpha</span><span class="p">))</span><span class="w">             </span><span class="n">me</span><span class="p">%</span><span class="n">alpha</span><span class="w">             </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">alpha</span><span class="p">)</span>
+<a id="ln-423" name="ln-423" href="#ln-423"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">alpha_min</span><span class="p">))</span><span class="w">         </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="w">         </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">alpha_min</span><span class="p">)</span>
+<a id="ln-424" name="ln-424" href="#ln-424"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">alpha_max</span><span class="p">))</span><span class="w">         </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="w">         </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">alpha_max</span><span class="p">)</span>
+<a id="ln-425" name="ln-425" href="#ln-425"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">tolx</span><span class="p">))</span><span class="w">              </span><span class="n">me</span><span class="p">%</span><span class="n">tolx</span><span class="w">              </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">tolx</span><span class="p">)</span>
+<a id="ln-426" name="ln-426" href="#ln-426"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">backtrack_c</span><span class="p">))</span><span class="w">       </span><span class="n">me</span><span class="p">%</span><span class="n">c</span><span class="w">                 </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">backtrack_c</span><span class="p">)</span>
+<a id="ln-427" name="ln-427" href="#ln-427"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">backtrack_tau</span><span class="p">))</span><span class="w">     </span><span class="n">me</span><span class="p">%</span><span class="n">tau</span><span class="w">               </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">backtrack_tau</span><span class="p">)</span>
+<a id="ln-428" name="ln-428" href="#ln-428"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">use_broyden</span><span class="p">))</span><span class="w">       </span><span class="n">me</span><span class="p">%</span><span class="n">use_broyden</span><span class="w">       </span><span class="o">=</span><span class="w"> </span><span class="n">use_broyden</span>
+<a id="ln-429" name="ln-429" href="#ln-429"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">broyden_update_n</span><span class="p">))</span><span class="w">  </span><span class="n">me</span><span class="p">%</span><span class="n">broyden_update_n</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">broyden_update_n</span><span class="p">)</span>
+<a id="ln-430" name="ln-430" href="#ln-430"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">verbose</span><span class="p">))</span><span class="w">           </span><span class="n">me</span><span class="p">%</span><span class="n">verbose</span><span class="w">           </span><span class="o">=</span><span class="w"> </span><span class="n">verbose</span>
+<a id="ln-431" name="ln-431" href="#ln-431"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">iunit</span><span class="p">))</span><span class="w">             </span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="w">             </span><span class="o">=</span><span class="w"> </span><span class="n">iunit</span>
+<a id="ln-432" name="ln-432" href="#ln-432"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">n_uphill_max</span><span class="p">))</span><span class="w">      </span><span class="n">me</span><span class="p">%</span><span class="n">n_uphill_max</span><span class="w">      </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">n_uphill_max</span><span class="p">)</span>
+<a id="ln-433" name="ln-433" href="#ln-433"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">n_intervals</span><span class="p">))</span><span class="w">       </span><span class="n">me</span><span class="p">%</span><span class="n">n_intervals</span><span class="w">       </span><span class="o">=</span><span class="w"> </span><span class="nb">max</span><span class="p">(</span><span class="nb">abs</span><span class="p">(</span><span class="n">n_intervals</span><span class="p">),</span><span class="mi">1</span><span class="p">)</span>
+<a id="ln-434" name="ln-434" href="#ln-434"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">fmin_tol</span><span class="p">))</span><span class="w">          </span><span class="n">me</span><span class="p">%</span><span class="n">fmin_tol</span><span class="w">          </span><span class="o">=</span><span class="w"> </span><span class="nb">abs</span><span class="p">(</span><span class="n">fmin_tol</span><span class="p">)</span>
+<a id="ln-435" name="ln-435" href="#ln-435"></a>
+<a id="ln-436" name="ln-436" href="#ln-436"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">export_iteration</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">export_iteration</span><span class="w">  </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">export_iteration</span>
+<a id="ln-437" name="ln-437" href="#ln-437"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">user_input_check</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">user_input_check</span><span class="w">  </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">user_input_check</span>
+<a id="ln-438" name="ln-438" href="#ln-438"></a>
+<a id="ln-439" name="ln-439" href="#ln-439"></a><span class="w">    </span><span class="c">! error checks:</span>
+<a id="ln-440" name="ln-440" href="#ln-440"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">alpha</span><span class="o">&lt;</span><span class="n">zero</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha</span><span class="o">&gt;</span><span class="n">one</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-441" name="ln-441" href="#ln-441"></a><span class="k">        </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
+<a id="ln-442" name="ln-442" href="#ln-442"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: invalid alpha:&#39;</span><span class="p">,</span><span class="n">r</span><span class="o">=</span><span class="n">me</span><span class="p">%</span><span class="n">alpha</span><span class="p">)</span>
+<a id="ln-443" name="ln-443" href="#ln-443"></a><span class="w">        </span><span class="k">return</span>
+<a id="ln-444" name="ln-444" href="#ln-444"></a><span class="k">    end if</span>
+<a id="ln-445" name="ln-445" href="#ln-445"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="o">&lt;</span><span class="n">zero</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="o">&gt;</span><span class="n">one</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-446" name="ln-446" href="#ln-446"></a><span class="k">        </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
+<a id="ln-447" name="ln-447" href="#ln-447"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: invalid alpha_min:&#39;</span><span class="p">,</span><span class="n">r</span><span class="o">=</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="p">)</span>
+<a id="ln-448" name="ln-448" href="#ln-448"></a><span class="w">        </span><span class="k">return</span>
+<a id="ln-449" name="ln-449" href="#ln-449"></a><span class="k">    end if</span>
+<a id="ln-450" name="ln-450" href="#ln-450"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="o">&lt;</span><span class="n">zero</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="o">&gt;</span><span class="n">one</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-451" name="ln-451" href="#ln-451"></a><span class="k">        </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
+<a id="ln-452" name="ln-452" href="#ln-452"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: invalid alpha_max:&#39;</span><span class="p">,</span><span class="n">r</span><span class="o">=</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="p">)</span>
+<a id="ln-453" name="ln-453" href="#ln-453"></a><span class="w">        </span><span class="k">return</span>
+<a id="ln-454" name="ln-454" href="#ln-454"></a><span class="k">    end if</span>
+<a id="ln-455" name="ln-455" href="#ln-455"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="o">&lt;=</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-456" name="ln-456" href="#ln-456"></a><span class="k">        </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
+<a id="ln-457" name="ln-457" href="#ln-457"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: alpha_min must be &lt; alpha_max&#39;</span><span class="p">)</span>
+<a id="ln-458" name="ln-458" href="#ln-458"></a><span class="w">        </span><span class="k">return</span>
+<a id="ln-459" name="ln-459" href="#ln-459"></a><span class="k">    end if</span>
+<a id="ln-460" name="ln-460" href="#ln-460"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">c</span><span class="o">&lt;</span><span class="n">zero</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">c</span><span class="o">&gt;</span><span class="n">one</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-461" name="ln-461" href="#ln-461"></a><span class="k">        </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
+<a id="ln-462" name="ln-462" href="#ln-462"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">12</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: backtracking linesearch c must be in range (0, 1):&#39;</span><span class="p">,</span><span class="n">r</span><span class="o">=</span><span class="n">me</span><span class="p">%</span><span class="n">c</span><span class="p">)</span>
+<a id="ln-463" name="ln-463" href="#ln-463"></a><span class="w">        </span><span class="k">return</span>
+<a id="ln-464" name="ln-464" href="#ln-464"></a><span class="k">    end if</span>
+<a id="ln-465" name="ln-465" href="#ln-465"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">tau</span><span class="o">&lt;</span><span class="n">zero</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">tau</span><span class="o">&gt;</span><span class="n">one</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-466" name="ln-466" href="#ln-466"></a><span class="k">        </span><span class="n">status_ok</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
+<a id="ln-467" name="ln-467" href="#ln-467"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">13</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: backtracking linesearch tau must be in range (0, 1):&#39;</span><span class="p">,</span><span class="n">r</span><span class="o">=</span><span class="n">me</span><span class="p">%</span><span class="n">tau</span><span class="p">)</span>
+<a id="ln-468" name="ln-468" href="#ln-468"></a><span class="w">        </span><span class="k">return</span>
+<a id="ln-469" name="ln-469" href="#ln-469"></a><span class="k">    end if</span>
+<a id="ln-470" name="ln-470" href="#ln-470"></a>
+<a id="ln-471" name="ln-471" href="#ln-471"></a><span class="w">    </span><span class="c">! initialize:</span>
+<a id="ln-472" name="ln-472" href="#ln-472"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">n_nonzeros</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">1</span><span class="w"> </span><span class="c">! not used</span>
+<a id="ln-473" name="ln-473" href="#ln-473"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">allocated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">irow</span><span class="p">))</span><span class="w"> </span><span class="k">deallocate</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">irow</span><span class="p">)</span>
+<a id="ln-474" name="ln-474" href="#ln-474"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">allocated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="p">))</span><span class="w"> </span><span class="k">deallocate</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="p">)</span>
+<a id="ln-475" name="ln-475" href="#ln-475"></a>
+<a id="ln-476" name="ln-476" href="#ln-476"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">sparsity_mode</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-477" name="ln-477" href="#ln-477"></a><span class="k">        </span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">sparsity_mode</span>
+<a id="ln-478" name="ln-478" href="#ln-478"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">sparsity_mode</span><span class="o">&gt;</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="k">then</span><span class="w"> </span><span class="c">! sparse solver method</span>
+<a id="ln-479" name="ln-479" href="#ln-479"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">irow</span><span class="p">)</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="nb">present</span><span class="p">(</span><span class="n">icol</span><span class="p">)</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="nb">present</span><span class="p">(</span><span class="n">grad_sparse</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-480" name="ln-480" href="#ln-480"></a><span class="k">                if</span><span class="w"> </span><span class="p">(</span><span class="n">size</span><span class="p">(</span><span class="n">irow</span><span class="p">)</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">size</span><span class="p">(</span><span class="n">icol</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-481" name="ln-481" href="#ln-481"></a><span class="k">                    </span><span class="n">me</span><span class="p">%</span><span class="n">n_nonzeros</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">size</span><span class="p">(</span><span class="n">irow</span><span class="p">)</span>
+<a id="ln-482" name="ln-482" href="#ln-482"></a><span class="w">                    </span><span class="n">me</span><span class="p">%</span><span class="n">irow</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">irow</span>
+<a id="ln-483" name="ln-483" href="#ln-483"></a><span class="w">                    </span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">icol</span>
+<a id="ln-484" name="ln-484" href="#ln-484"></a><span class="w">                </span><span class="k">else</span>
+<a id="ln-485" name="ln-485" href="#ln-485"></a><span class="k">                    call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">15</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: irow and icol must be the same length&#39;</span><span class="p">)</span>
+<a id="ln-486" name="ln-486" href="#ln-486"></a><span class="w">                    </span><span class="k">return</span>
+<a id="ln-487" name="ln-487" href="#ln-487"></a><span class="k">                end if</span>
+<a id="ln-488" name="ln-488" href="#ln-488"></a><span class="k">            else</span>
+<a id="ln-489" name="ln-489" href="#ln-489"></a><span class="k">                call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">14</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: must specify grad_sparse, irow, and icol for sparsity_mode &gt; 1&#39;</span><span class="p">)</span>
+<a id="ln-490" name="ln-490" href="#ln-490"></a><span class="w">                </span><span class="k">return</span>
+<a id="ln-491" name="ln-491" href="#ln-491"></a><span class="k">            end if</span>
+<a id="ln-492" name="ln-492" href="#ln-492"></a><span class="w">            </span><span class="c">! LSQR optional inputs:</span>
+<a id="ln-493" name="ln-493" href="#ln-493"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">atol</span><span class="p">))</span><span class="w">   </span><span class="n">me</span><span class="p">%</span><span class="n">atol</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="n">atol</span>
+<a id="ln-494" name="ln-494" href="#ln-494"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">btol</span><span class="p">))</span><span class="w">   </span><span class="n">me</span><span class="p">%</span><span class="n">btol</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="n">btol</span>
+<a id="ln-495" name="ln-495" href="#ln-495"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">conlim</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">conlim</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">conlim</span>
+<a id="ln-496" name="ln-496" href="#ln-496"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">damp</span><span class="p">))</span><span class="w">   </span><span class="n">me</span><span class="p">%</span><span class="n">damp</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="n">damp</span>
+<a id="ln-497" name="ln-497" href="#ln-497"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">itnlim</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">itnlim</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">itnlim</span>
+<a id="ln-498" name="ln-498" href="#ln-498"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">nout</span><span class="p">))</span><span class="w">   </span><span class="n">me</span><span class="p">%</span><span class="n">nout</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="n">nout</span>
+<a id="ln-499" name="ln-499" href="#ln-499"></a>
+<a id="ln-500" name="ln-500" href="#ln-500"></a><span class="w">            </span><span class="c">! LUSOL method</span>
+<a id="ln-501" name="ln-501" href="#ln-501"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">nout</span><span class="p">))</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">lusol_method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">lusol_method</span>
+<a id="ln-502" name="ln-502" href="#ln-502"></a>
+<a id="ln-503" name="ln-503" href="#ln-503"></a><span class="w">        </span><span class="k">end if</span>
 <a id="ln-504" name="ln-504" href="#ln-504"></a><span class="k">    end if</span>
 <a id="ln-505" name="ln-505" href="#ln-505"></a>
 <a id="ln-506" name="ln-506" href="#ln-506"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">status_ok</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
@@ -677,618 +677,661 @@ <h2><span class="anchor" id="src"></span>Source Code</h2>
 <a id="ln-521" name="ln-521" href="#ln-521"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
 <a id="ln-522" name="ln-522" href="#ln-522"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span>
 <a id="ln-523" name="ln-523" href="#ln-523"></a>
-<a id="ln-524" name="ln-524" href="#ln-524"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec</span><span class="w">            </span><span class="c">!! function vector</span>
-<a id="ln-525" name="ln-525" href="#ln-525"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac</span><span class="w">            </span><span class="c">!! jacobian matrix [dense]</span>
-<a id="ln-526" name="ln-526" href="#ln-526"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="w">  </span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac_sparse</span><span class="w">     </span><span class="c">!! jacobian matrix [sparse]</span>
-<a id="ln-527" name="ln-527" href="#ln-527"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">rhs</span><span class="w">             </span><span class="c">!! linear system right-hand side</span>
-<a id="ln-528" name="ln-528" href="#ln-528"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">p</span><span class="w">               </span><span class="c">!! search direction</span>
-<a id="ln-529" name="ln-529" href="#ln-529"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xold</span><span class="w">            </span><span class="c">!! previous value of `x`</span>
-<a id="ln-530" name="ln-530" href="#ln-530"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">prev_fvec</span><span class="w">       </span><span class="c">!! previous function vector</span>
-<a id="ln-531" name="ln-531" href="#ln-531"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">prev_fjac</span><span class="w">       </span><span class="c">!! previous jacobian matrix</span>
-<a id="ln-532" name="ln-532" href="#ln-532"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">delf</span><span class="w">            </span><span class="c">!! used for Broyden (rank 2 for `matmul`)</span>
-<a id="ln-533" name="ln-533" href="#ln-533"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">delx</span><span class="w">            </span><span class="c">!! used for Broyden (rank 2 for `matmul`)</span>
-<a id="ln-534" name="ln-534" href="#ln-534"></a><span class="w">    </span><span class="kt">logical</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">user_stop</span><span class="w">       </span><span class="c">!! user stop button flag</span>
-<a id="ln-535" name="ln-535" href="#ln-535"></a><span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">info</span><span class="w">            </span><span class="c">!! status flag from the [[linear_solver]]</span>
-<a id="ln-536" name="ln-536" href="#ln-536"></a><span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">iter</span><span class="w">            </span><span class="c">!! iteration counter</span>
-<a id="ln-537" name="ln-537" href="#ln-537"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">                            </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span><span class="w">               </span><span class="c">!! magnitude of `fvec`</span>
-<a id="ln-538" name="ln-538" href="#ln-538"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">                            </span><span class="kd">::</span><span class="w"> </span><span class="n">fold</span><span class="w">            </span><span class="c">!! previous value of `f`</span>
-<a id="ln-539" name="ln-539" href="#ln-539"></a><span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">n_uphill</span><span class="w">        </span><span class="c">!! number of steps taken in the &quot;uphill&quot; direction</span>
-<a id="ln-540" name="ln-540" href="#ln-540"></a><span class="w">                                                           </span><span class="c">!! (where `f` is increasing)</span>
-<a id="ln-541" name="ln-541" href="#ln-541"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">                            </span><span class="kd">::</span><span class="w"> </span><span class="n">delxmag2</span><span class="w">        </span><span class="c">!! used for Broyden</span>
-<a id="ln-542" name="ln-542" href="#ln-542"></a><span class="w">    </span><span class="kt">logical</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">recompute_jac</span><span class="w">   </span><span class="c">!! if using Broyden, and we want to call the user</span>
-<a id="ln-543" name="ln-543" href="#ln-543"></a><span class="w">                                                           </span><span class="c">!! jacobian routine instead</span>
-<a id="ln-544" name="ln-544" href="#ln-544"></a><span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">broyden_counter</span><span class="w"> </span><span class="c">!! number of times the broyden update has been used</span>
-<a id="ln-545" name="ln-545" href="#ln-545"></a><span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">alloc_stat</span><span class="w">      </span><span class="c">!! allocation status flag</span>
-<a id="ln-546" name="ln-546" href="#ln-546"></a><span class="w">    </span><span class="k">type</span><span class="p">(</span><span class="n">lsqr_solver_ez</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">sparse_solver</span><span class="w">  </span><span class="c">!! sparse LSQR solver class</span>
-<a id="ln-547" name="ln-547" href="#ln-547"></a><span class="w">    </span><span class="k">type</span><span class="p">(</span><span class="n">lusol_settings</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">lusol_options</span>
-<a id="ln-548" name="ln-548" href="#ln-548"></a>
-<a id="ln-549" name="ln-549" href="#ln-549"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">istat</span><span class="o">&lt;</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="c">! class was not initialized properly</span>
-<a id="ln-550" name="ln-550" href="#ln-550"></a>
-<a id="ln-551" name="ln-551" href="#ln-551"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(.</span><span class="nb">not</span><span class="p">.</span><span class="w"> </span><span class="nb">associated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-552" name="ln-552" href="#ln-552"></a><span class="k">        call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: function routine is not associated&#39;</span><span class="p">)</span>
-<a id="ln-553" name="ln-553" href="#ln-553"></a><span class="w">        </span><span class="k">return</span>
-<a id="ln-554" name="ln-554" href="#ln-554"></a><span class="k">    end if</span>
-<a id="ln-555" name="ln-555" href="#ln-555"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="o">==</span><span class="mi">1</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="nb">not</span><span class="p">.</span><span class="w"> </span><span class="nb">associated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">grad</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-556" name="ln-556" href="#ln-556"></a><span class="k">        call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">11</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: gradient routine is not associated&#39;</span><span class="p">)</span>
+<a id="ln-524" name="ln-524" href="#ln-524"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec</span><span class="w">             </span><span class="c">!! function vector</span>
+<a id="ln-525" name="ln-525" href="#ln-525"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac</span><span class="w">             </span><span class="c">!! jacobian matrix [dense]</span>
+<a id="ln-526" name="ln-526" href="#ln-526"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="w">  </span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac_sparse</span><span class="w">      </span><span class="c">!! jacobian matrix [sparse]</span>
+<a id="ln-527" name="ln-527" href="#ln-527"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="w">  </span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">prev_fjac_sparse</span><span class="w"> </span><span class="c">!! previous jacobian matrix [sparse]</span>
+<a id="ln-528" name="ln-528" href="#ln-528"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">rhs</span><span class="w">              </span><span class="c">!! linear system right-hand side</span>
+<a id="ln-529" name="ln-529" href="#ln-529"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">p</span><span class="w">                </span><span class="c">!! search direction</span>
+<a id="ln-530" name="ln-530" href="#ln-530"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xold</span><span class="w">             </span><span class="c">!! previous value of `x`</span>
+<a id="ln-531" name="ln-531" href="#ln-531"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:)</span><span class="w">  </span><span class="p">,</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">prev_fvec</span><span class="w">        </span><span class="c">!! previous function vector</span>
+<a id="ln-532" name="ln-532" href="#ln-532"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">prev_fjac</span><span class="w">        </span><span class="c">!! previous jacobian matrix</span>
+<a id="ln-533" name="ln-533" href="#ln-533"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">delf</span><span class="w">             </span><span class="c">!! used for Broyden (rank 2 for `matmul`)</span>
+<a id="ln-534" name="ln-534" href="#ln-534"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">delx</span><span class="w">             </span><span class="c">!! used for Broyden (rank 2 for `matmul`)</span>
+<a id="ln-535" name="ln-535" href="#ln-535"></a><span class="w">    </span><span class="kt">logical</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">user_stop</span><span class="w">        </span><span class="c">!! user stop button flag</span>
+<a id="ln-536" name="ln-536" href="#ln-536"></a><span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">info</span><span class="w">             </span><span class="c">!! status flag from the [[linear_solver]]</span>
+<a id="ln-537" name="ln-537" href="#ln-537"></a><span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">iter</span><span class="w">             </span><span class="c">!! iteration counter</span>
+<a id="ln-538" name="ln-538" href="#ln-538"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">                            </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span><span class="w">                </span><span class="c">!! magnitude of `fvec`</span>
+<a id="ln-539" name="ln-539" href="#ln-539"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">                            </span><span class="kd">::</span><span class="w"> </span><span class="n">fold</span><span class="w">             </span><span class="c">!! previous value of `f`</span>
+<a id="ln-540" name="ln-540" href="#ln-540"></a><span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">n_uphill</span><span class="w">         </span><span class="c">!! number of steps taken in the &quot;uphill&quot; direction</span>
+<a id="ln-541" name="ln-541" href="#ln-541"></a><span class="w">                                                            </span><span class="c">!! (where `f` is increasing)</span>
+<a id="ln-542" name="ln-542" href="#ln-542"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">                            </span><span class="kd">::</span><span class="w"> </span><span class="n">delxmag2</span><span class="w">         </span><span class="c">!! used for Broyden</span>
+<a id="ln-543" name="ln-543" href="#ln-543"></a><span class="w">    </span><span class="kt">logical</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">recompute_jac</span><span class="w">    </span><span class="c">!! if using Broyden, and we want to call the user</span>
+<a id="ln-544" name="ln-544" href="#ln-544"></a><span class="w">                                                            </span><span class="c">!! jacobian routine instead</span>
+<a id="ln-545" name="ln-545" href="#ln-545"></a><span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">broyden_counter</span><span class="w">  </span><span class="c">!! number of times the broyden update has been used</span>
+<a id="ln-546" name="ln-546" href="#ln-546"></a><span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">alloc_stat</span><span class="w">       </span><span class="c">!! allocation status flag</span>
+<a id="ln-547" name="ln-547" href="#ln-547"></a><span class="w">    </span><span class="k">type</span><span class="p">(</span><span class="n">lsqr_solver_ez</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">sparse_solver</span><span class="w">  </span><span class="c">!! sparse LSQR solver class</span>
+<a id="ln-548" name="ln-548" href="#ln-548"></a><span class="w">    </span><span class="k">type</span><span class="p">(</span><span class="n">lusol_settings</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">lusol_options</span>
+<a id="ln-549" name="ln-549" href="#ln-549"></a><span class="w">    </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="c">!! counter</span>
+<a id="ln-550" name="ln-550" href="#ln-550"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">idx</span><span class="p">,</span><span class="w"> </span><span class="n">index_array</span><span class="w"> </span><span class="c">!! for sparse indexing</span>
+<a id="ln-551" name="ln-551" href="#ln-551"></a><span class="w">    </span><span class="kt">character</span><span class="p">(</span><span class="nb">len</span><span class="o">=</span><span class="mi">10</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">i_str</span><span class="w"> </span><span class="c">!! string version of `i` for row string</span>
+<a id="ln-552" name="ln-552" href="#ln-552"></a>
+<a id="ln-553" name="ln-553" href="#ln-553"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">istat</span><span class="o">&lt;</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="c">! class was not initialized properly</span>
+<a id="ln-554" name="ln-554" href="#ln-554"></a>
+<a id="ln-555" name="ln-555" href="#ln-555"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(.</span><span class="nb">not</span><span class="p">.</span><span class="w"> </span><span class="nb">associated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-556" name="ln-556" href="#ln-556"></a><span class="k">        call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">10</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: function routine is not associated&#39;</span><span class="p">)</span>
 <a id="ln-557" name="ln-557" href="#ln-557"></a><span class="w">        </span><span class="k">return</span>
 <a id="ln-558" name="ln-558" href="#ln-558"></a><span class="k">    end if</span>
-<a id="ln-559" name="ln-559" href="#ln-559"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="o">&gt;</span><span class="mi">1</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="nb">not</span><span class="p">.</span><span class="w"> </span><span class="nb">associated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">grad_sparse</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-559" name="ln-559" href="#ln-559"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="o">==</span><span class="mi">1</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="nb">not</span><span class="p">.</span><span class="w"> </span><span class="nb">associated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">grad</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
 <a id="ln-560" name="ln-560" href="#ln-560"></a><span class="k">        call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">11</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: gradient routine is not associated&#39;</span><span class="p">)</span>
 <a id="ln-561" name="ln-561" href="#ln-561"></a><span class="w">        </span><span class="k">return</span>
 <a id="ln-562" name="ln-562" href="#ln-562"></a><span class="k">    end if</span>
-<a id="ln-563" name="ln-563" href="#ln-563"></a>
-<a id="ln-564" name="ln-564" href="#ln-564"></a><span class="w">    </span><span class="c">! initialize:</span>
-<a id="ln-565" name="ln-565" href="#ln-565"></a><span class="w">    </span><span class="n">iter</span><span class="w">            </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
-<a id="ln-566" name="ln-566" href="#ln-566"></a><span class="w">    </span><span class="n">n_uphill</span><span class="w">        </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
-<a id="ln-567" name="ln-567" href="#ln-567"></a><span class="w">    </span><span class="n">recompute_jac</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
-<a id="ln-568" name="ln-568" href="#ln-568"></a><span class="w">    </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
-<a id="ln-569" name="ln-569" href="#ln-569"></a>
-<a id="ln-570" name="ln-570" href="#ln-570"></a><span class="w">    </span><span class="c">! allocate the arrays:</span>
-<a id="ln-571" name="ln-571" href="#ln-571"></a><span class="w">    </span><span class="n">alloc_stat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
-<a id="ln-572" name="ln-572" href="#ln-572"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">fvec</span><span class="w">     </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">)</span><span class="w">      </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<a id="ln-563" name="ln-563" href="#ln-563"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="o">&gt;</span><span class="mi">1</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="nb">not</span><span class="p">.</span><span class="w"> </span><span class="nb">associated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">grad_sparse</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-564" name="ln-564" href="#ln-564"></a><span class="k">        call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">11</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: gradient routine is not associated&#39;</span><span class="p">)</span>
+<a id="ln-565" name="ln-565" href="#ln-565"></a><span class="w">        </span><span class="k">return</span>
+<a id="ln-566" name="ln-566" href="#ln-566"></a><span class="k">    end if</span>
+<a id="ln-567" name="ln-567" href="#ln-567"></a>
+<a id="ln-568" name="ln-568" href="#ln-568"></a><span class="w">    </span><span class="c">! initialize:</span>
+<a id="ln-569" name="ln-569" href="#ln-569"></a><span class="w">    </span><span class="n">iter</span><span class="w">            </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
+<a id="ln-570" name="ln-570" href="#ln-570"></a><span class="w">    </span><span class="n">n_uphill</span><span class="w">        </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
+<a id="ln-571" name="ln-571" href="#ln-571"></a><span class="w">    </span><span class="n">recompute_jac</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
+<a id="ln-572" name="ln-572" href="#ln-572"></a><span class="w">    </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
 <a id="ln-573" name="ln-573" href="#ln-573"></a>
-<a id="ln-574" name="ln-574" href="#ln-574"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="o">==</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-575" name="ln-575" href="#ln-575"></a><span class="w">        </span><span class="c">! dense</span>
-<a id="ln-576" name="ln-576" href="#ln-576"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">fjac</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
-<a id="ln-577" name="ln-577" href="#ln-577"></a><span class="w">    </span><span class="k">else</span>
-<a id="ln-578" name="ln-578" href="#ln-578"></a><span class="w">        </span><span class="c">! sparse</span>
-<a id="ln-579" name="ln-579" href="#ln-579"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">fjac_sparse</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n_nonzeros</span><span class="p">)</span><span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
-<a id="ln-580" name="ln-580" href="#ln-580"></a><span class="w">    </span><span class="k">end if</span>
-<a id="ln-581" name="ln-581" href="#ln-581"></a>
-<a id="ln-582" name="ln-582" href="#ln-582"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">rhs</span><span class="w">      </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">)</span><span class="w">      </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
-<a id="ln-583" name="ln-583" href="#ln-583"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">p</span><span class="w">        </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">)</span><span class="w">      </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
-<a id="ln-584" name="ln-584" href="#ln-584"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">xold</span><span class="w">     </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">)</span><span class="w">      </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
-<a id="ln-585" name="ln-585" href="#ln-585"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">use_broyden</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-586" name="ln-586" href="#ln-586"></a><span class="w">        </span><span class="c">! only need these for broyden:</span>
-<a id="ln-587" name="ln-587" href="#ln-587"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">prev_fvec</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">)</span><span class="w">      </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
-<a id="ln-588" name="ln-588" href="#ln-588"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">prev_fjac</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
-<a id="ln-589" name="ln-589" href="#ln-589"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">delf</span><span class="w">     </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span><span class="w">    </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
-<a id="ln-590" name="ln-590" href="#ln-590"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">delx</span><span class="w">     </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span><span class="w">    </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
-<a id="ln-591" name="ln-591" href="#ln-591"></a><span class="w">    </span><span class="k">end if</span>
-<a id="ln-592" name="ln-592" href="#ln-592"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">/=</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-593" name="ln-593" href="#ln-593"></a><span class="k">        call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: Out of memory&#39;</span><span class="p">)</span>
-<a id="ln-594" name="ln-594" href="#ln-594"></a><span class="w">        </span><span class="k">return</span>
-<a id="ln-595" name="ln-595" href="#ln-595"></a><span class="k">    else</span>
-<a id="ln-596" name="ln-596" href="#ln-596"></a><span class="k">        </span><span class="n">me</span><span class="p">%</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">998</span>
-<a id="ln-597" name="ln-597" href="#ln-597"></a><span class="w">        </span><span class="n">me</span><span class="p">%</span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Unknown error&#39;</span>
-<a id="ln-598" name="ln-598" href="#ln-598"></a><span class="w">    </span><span class="k">end if</span>
-<a id="ln-599" name="ln-599" href="#ln-599"></a>
-<a id="ln-600" name="ln-600" href="#ln-600"></a><span class="w">    </span><span class="c">! evaluate the function:</span>
-<a id="ln-601" name="ln-601" href="#ln-601"></a><span class="w">    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fvec</span><span class="p">)</span>
-<a id="ln-602" name="ln-602" href="#ln-602"></a><span class="w">    </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">norm2</span><span class="p">(</span><span class="n">fvec</span><span class="p">)</span>
-<a id="ln-603" name="ln-603" href="#ln-603"></a>
-<a id="ln-604" name="ln-604" href="#ln-604"></a><span class="w">    </span><span class="c">! check to see if initial guess is a root:</span>
-<a id="ln-605" name="ln-605" href="#ln-605"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">f</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">tol</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-606" name="ln-606" href="#ln-606"></a>
-<a id="ln-607" name="ln-607" href="#ln-607"></a><span class="k">        call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Required accuracy achieved&#39;</span><span class="p">)</span>
-<a id="ln-608" name="ln-608" href="#ln-608"></a>
-<a id="ln-609" name="ln-609" href="#ln-609"></a><span class="w">    </span><span class="k">else</span>
-<a id="ln-610" name="ln-610" href="#ln-610"></a>
-<a id="ln-611" name="ln-611" href="#ln-611"></a><span class="w">        </span><span class="c">! main iteration loop:</span>
-<a id="ln-612" name="ln-612" href="#ln-612"></a><span class="w">        </span><span class="k">do </span><span class="n">iter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">max_iter</span>
-<a id="ln-613" name="ln-613" href="#ln-613"></a>
-<a id="ln-614" name="ln-614" href="#ln-614"></a><span class="w">            </span><span class="c">! Export the current iteration:</span>
-<a id="ln-615" name="ln-615" href="#ln-615"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">associated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">export_iteration</span><span class="p">))</span><span class="w"> </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">export_iteration</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">iter</span><span class="p">)</span>
+<a id="ln-574" name="ln-574" href="#ln-574"></a><span class="w">    </span><span class="c">! allocate the arrays:</span>
+<a id="ln-575" name="ln-575" href="#ln-575"></a><span class="w">    </span><span class="n">alloc_stat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
+<a id="ln-576" name="ln-576" href="#ln-576"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">fvec</span><span class="w">     </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">)</span><span class="w">      </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<a id="ln-577" name="ln-577" href="#ln-577"></a>
+<a id="ln-578" name="ln-578" href="#ln-578"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="o">==</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-579" name="ln-579" href="#ln-579"></a><span class="w">        </span><span class="c">! dense</span>
+<a id="ln-580" name="ln-580" href="#ln-580"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">fjac</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<a id="ln-581" name="ln-581" href="#ln-581"></a><span class="w">    </span><span class="k">else</span>
+<a id="ln-582" name="ln-582" href="#ln-582"></a><span class="w">        </span><span class="c">! sparse</span>
+<a id="ln-583" name="ln-583" href="#ln-583"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">fjac_sparse</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n_nonzeros</span><span class="p">)</span><span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<a id="ln-584" name="ln-584" href="#ln-584"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">use_broyden</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">prev_fjac_sparse</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n_nonzeros</span><span class="p">)</span><span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<a id="ln-585" name="ln-585" href="#ln-585"></a><span class="w">    </span><span class="k">end if</span>
+<a id="ln-586" name="ln-586" href="#ln-586"></a>
+<a id="ln-587" name="ln-587" href="#ln-587"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">rhs</span><span class="w">      </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">)</span><span class="w">      </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<a id="ln-588" name="ln-588" href="#ln-588"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">p</span><span class="w">        </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">)</span><span class="w">      </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<a id="ln-589" name="ln-589" href="#ln-589"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">xold</span><span class="w">     </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">)</span><span class="w">      </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<a id="ln-590" name="ln-590" href="#ln-590"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">use_broyden</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-591" name="ln-591" href="#ln-591"></a><span class="w">        </span><span class="c">! only need these for broyden:</span>
+<a id="ln-592" name="ln-592" href="#ln-592"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">prev_fvec</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">)</span><span class="w">      </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<a id="ln-593" name="ln-593" href="#ln-593"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="o">/=</span><span class="mi">1</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-594" name="ln-594" href="#ln-594"></a><span class="k">            allocate</span><span class="p">(</span><span class="n">prev_fjac</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">)</span><span class="w"> </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<a id="ln-595" name="ln-595" href="#ln-595"></a><span class="w">            </span><span class="n">index_array</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">[(</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n_nonzeros</span><span class="p">)]</span><span class="w"> </span><span class="c">! an array to index the sparse jacobian elements</span>
+<a id="ln-596" name="ln-596" href="#ln-596"></a><span class="w">        </span><span class="k">end if</span>
+<a id="ln-597" name="ln-597" href="#ln-597"></a><span class="k">        if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">delf</span><span class="w">     </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span><span class="w">    </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<a id="ln-598" name="ln-598" href="#ln-598"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">allocate</span><span class="p">(</span><span class="n">delx</span><span class="w">     </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span><span class="w">    </span><span class="p">,</span><span class="w"> </span><span class="nb">stat</span><span class="o">=</span><span class="n">alloc_stat</span><span class="p">)</span>
+<a id="ln-599" name="ln-599" href="#ln-599"></a><span class="w">    </span><span class="k">end if</span>
+<a id="ln-600" name="ln-600" href="#ln-600"></a><span class="k">    if</span><span class="w"> </span><span class="p">(</span><span class="n">alloc_stat</span><span class="o">/=</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-601" name="ln-601" href="#ln-601"></a><span class="k">        call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: Out of memory&#39;</span><span class="p">)</span>
+<a id="ln-602" name="ln-602" href="#ln-602"></a><span class="w">        </span><span class="k">return</span>
+<a id="ln-603" name="ln-603" href="#ln-603"></a><span class="k">    else</span>
+<a id="ln-604" name="ln-604" href="#ln-604"></a><span class="k">        </span><span class="n">me</span><span class="p">%</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">998</span>
+<a id="ln-605" name="ln-605" href="#ln-605"></a><span class="w">        </span><span class="n">me</span><span class="p">%</span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Unknown error&#39;</span>
+<a id="ln-606" name="ln-606" href="#ln-606"></a><span class="w">    </span><span class="k">end if</span>
+<a id="ln-607" name="ln-607" href="#ln-607"></a>
+<a id="ln-608" name="ln-608" href="#ln-608"></a><span class="w">    </span><span class="c">! evaluate the function:</span>
+<a id="ln-609" name="ln-609" href="#ln-609"></a><span class="w">    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fvec</span><span class="p">)</span>
+<a id="ln-610" name="ln-610" href="#ln-610"></a><span class="w">    </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">norm2</span><span class="p">(</span><span class="n">fvec</span><span class="p">)</span>
+<a id="ln-611" name="ln-611" href="#ln-611"></a>
+<a id="ln-612" name="ln-612" href="#ln-612"></a><span class="w">    </span><span class="c">! check to see if initial guess is a root:</span>
+<a id="ln-613" name="ln-613" href="#ln-613"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">f</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">tol</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-614" name="ln-614" href="#ln-614"></a>
+<a id="ln-615" name="ln-615" href="#ln-615"></a><span class="k">        call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Required accuracy achieved&#39;</span><span class="p">)</span>
 <a id="ln-616" name="ln-616" href="#ln-616"></a>
-<a id="ln-617" name="ln-617" href="#ln-617"></a><span class="w">            </span><span class="c">! Check for user stop:</span>
-<a id="ln-618" name="ln-618" href="#ln-618"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">associated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">user_input_check</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-619" name="ln-619" href="#ln-619"></a><span class="k">                call </span><span class="n">me</span><span class="p">%</span><span class="n">user_input_check</span><span class="p">(</span><span class="n">user_stop</span><span class="p">)</span>
-<a id="ln-620" name="ln-620" href="#ln-620"></a><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">user_stop</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-621" name="ln-621" href="#ln-621"></a><span class="k">                    call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Stopped by the user&#39;</span><span class="p">)</span>
-<a id="ln-622" name="ln-622" href="#ln-622"></a><span class="w">                    </span><span class="k">exit</span>
-<a id="ln-623" name="ln-623" href="#ln-623"></a><span class="k">                end if</span>
-<a id="ln-624" name="ln-624" href="#ln-624"></a><span class="k">            end if</span>
-<a id="ln-625" name="ln-625" href="#ln-625"></a>
-<a id="ln-626" name="ln-626" href="#ln-626"></a><span class="k">            if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">use_broyden</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="nb">not</span><span class="p">.</span><span class="w"> </span><span class="n">recompute_jac</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-627" name="ln-627" href="#ln-627"></a><span class="k">                if</span><span class="w"> </span><span class="p">(</span><span class="n">iter</span><span class="o">==</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-628" name="ln-628" href="#ln-628"></a><span class="w">                    </span><span class="c">! always compute Jacobian on the first iteration</span>
-<a id="ln-629" name="ln-629" href="#ln-629"></a><span class="w">                    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">grad</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fjac</span><span class="p">)</span>
-<a id="ln-630" name="ln-630" href="#ln-630"></a><span class="w">                    </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
-<a id="ln-631" name="ln-631" href="#ln-631"></a><span class="w">                </span><span class="k">else</span>
-<a id="ln-632" name="ln-632" href="#ln-632"></a><span class="w">                    </span><span class="c">! and use Broyden update to estimate Jacobian</span>
-<a id="ln-633" name="ln-633" href="#ln-633"></a><span class="w">                    </span><span class="c">! for subsequent iterations.</span>
-<a id="ln-634" name="ln-634" href="#ln-634"></a>
-<a id="ln-635" name="ln-635" href="#ln-635"></a><span class="w">                    </span><span class="c">! note: fvec was computed the last iteration</span>
-<a id="ln-636" name="ln-636" href="#ln-636"></a><span class="w">                    </span><span class="n">delx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">xold</span>
-<a id="ln-637" name="ln-637" href="#ln-637"></a><span class="w">                    </span><span class="n">delf</span><span class="p">(:,</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fvec</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">prev_fvec</span>
-<a id="ln-638" name="ln-638" href="#ln-638"></a><span class="w">                    </span><span class="n">delxmag2</span><span class="w">  </span><span class="o">=</span><span class="w"> </span><span class="nb">dot_product</span><span class="p">(</span><span class="n">delx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">),</span><span class="n">delx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">))</span>
-<a id="ln-639" name="ln-639" href="#ln-639"></a>
-<a id="ln-640" name="ln-640" href="#ln-640"></a><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">delxmag2</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">eps</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-641" name="ln-641" href="#ln-641"></a><span class="k">                        call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
-<a id="ln-642" name="ln-642" href="#ln-642"></a><span class="w">                                </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: Divide by zero when computing Broyden update&#39;</span><span class="p">)</span>
-<a id="ln-643" name="ln-643" href="#ln-643"></a><span class="w">                        </span><span class="k">exit</span>
-<a id="ln-644" name="ln-644" href="#ln-644"></a><span class="k">                    end if</span>
-<a id="ln-645" name="ln-645" href="#ln-645"></a>
-<a id="ln-646" name="ln-646" href="#ln-646"></a><span class="w">                    </span><span class="c">! Jacobian estimate:</span>
-<a id="ln-647" name="ln-647" href="#ln-647"></a><span class="w">                    </span><span class="n">fjac</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">prev_fjac</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">&amp;</span>
-<a id="ln-648" name="ln-648" href="#ln-648"></a><span class="w">                           </span><span class="nb">matmul</span><span class="p">((</span><span class="n">delf</span><span class="o">-</span><span class="nb">matmul</span><span class="p">(</span><span class="n">prev_fjac</span><span class="p">,</span><span class="n">delx</span><span class="p">)),&amp;</span>
-<a id="ln-649" name="ln-649" href="#ln-649"></a><span class="w">                           </span><span class="nb">transpose</span><span class="p">(</span><span class="n">delx</span><span class="p">))</span><span class="o">/</span><span class="n">delxmag2</span>
-<a id="ln-650" name="ln-650" href="#ln-650"></a>
-<a id="ln-651" name="ln-651" href="#ln-651"></a><span class="w">                    </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span>
-<a id="ln-652" name="ln-652" href="#ln-652"></a><span class="w">                </span><span class="k">end if</span>
-<a id="ln-653" name="ln-653" href="#ln-653"></a><span class="k">                </span><span class="n">prev_fjac</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fjac</span>
-<a id="ln-654" name="ln-654" href="#ln-654"></a><span class="w">                </span><span class="n">prev_fvec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fvec</span>
-<a id="ln-655" name="ln-655" href="#ln-655"></a><span class="w">            </span><span class="k">else</span>
-<a id="ln-656" name="ln-656" href="#ln-656"></a><span class="w">                </span><span class="c">! compute the jacobian:</span>
-<a id="ln-657" name="ln-657" href="#ln-657"></a><span class="w">                </span><span class="k">select case</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="p">)</span>
-<a id="ln-658" name="ln-658" href="#ln-658"></a><span class="w">                </span><span class="k">case</span><span class="w"> </span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
-<a id="ln-659" name="ln-659" href="#ln-659"></a><span class="w">                    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">grad</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fjac</span><span class="p">)</span>
-<a id="ln-660" name="ln-660" href="#ln-660"></a><span class="w">                </span><span class="k">case</span><span class="w"> </span><span class="p">(</span><span class="mi">2</span><span class="p">:)</span>
-<a id="ln-661" name="ln-661" href="#ln-661"></a><span class="w">                    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">grad_sparse</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
-<a id="ln-662" name="ln-662" href="#ln-662"></a><span class="w">                </span><span class="k">end select</span>
-<a id="ln-663" name="ln-663" href="#ln-663"></a><span class="k">                </span><span class="n">recompute_jac</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span><span class="w">  </span><span class="c">! for broyden</span>
-<a id="ln-664" name="ln-664" href="#ln-664"></a><span class="w">                </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
-<a id="ln-665" name="ln-665" href="#ln-665"></a><span class="w">            </span><span class="k">end if</span>
-<a id="ln-666" name="ln-666" href="#ln-666"></a>
-<a id="ln-667" name="ln-667" href="#ln-667"></a><span class="k">            </span><span class="n">xold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">x</span>
-<a id="ln-668" name="ln-668" href="#ln-668"></a><span class="w">            </span><span class="n">fold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">f</span>
+<a id="ln-617" name="ln-617" href="#ln-617"></a><span class="w">    </span><span class="k">else</span>
+<a id="ln-618" name="ln-618" href="#ln-618"></a>
+<a id="ln-619" name="ln-619" href="#ln-619"></a><span class="w">        </span><span class="c">! main iteration loop:</span>
+<a id="ln-620" name="ln-620" href="#ln-620"></a><span class="w">        </span><span class="k">do </span><span class="n">iter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">max_iter</span>
+<a id="ln-621" name="ln-621" href="#ln-621"></a>
+<a id="ln-622" name="ln-622" href="#ln-622"></a><span class="w">            </span><span class="c">! Export the current iteration:</span>
+<a id="ln-623" name="ln-623" href="#ln-623"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">associated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">export_iteration</span><span class="p">))</span><span class="w"> </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">export_iteration</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">iter</span><span class="p">)</span>
+<a id="ln-624" name="ln-624" href="#ln-624"></a>
+<a id="ln-625" name="ln-625" href="#ln-625"></a><span class="w">            </span><span class="c">! Check for user stop:</span>
+<a id="ln-626" name="ln-626" href="#ln-626"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">associated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">user_input_check</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-627" name="ln-627" href="#ln-627"></a><span class="k">                call </span><span class="n">me</span><span class="p">%</span><span class="n">user_input_check</span><span class="p">(</span><span class="n">user_stop</span><span class="p">)</span>
+<a id="ln-628" name="ln-628" href="#ln-628"></a><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">user_stop</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-629" name="ln-629" href="#ln-629"></a><span class="k">                    call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Stopped by the user&#39;</span><span class="p">)</span>
+<a id="ln-630" name="ln-630" href="#ln-630"></a><span class="w">                    </span><span class="k">exit</span>
+<a id="ln-631" name="ln-631" href="#ln-631"></a><span class="k">                end if</span>
+<a id="ln-632" name="ln-632" href="#ln-632"></a><span class="k">            end if</span>
+<a id="ln-633" name="ln-633" href="#ln-633"></a>
+<a id="ln-634" name="ln-634" href="#ln-634"></a><span class="k">            if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">use_broyden</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="p">.</span><span class="nb">not</span><span class="p">.</span><span class="w"> </span><span class="n">recompute_jac</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-635" name="ln-635" href="#ln-635"></a><span class="k">                if</span><span class="w"> </span><span class="p">(</span><span class="n">iter</span><span class="o">==</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-636" name="ln-636" href="#ln-636"></a><span class="w">                    </span><span class="c">! always compute Jacobian on the first iteration</span>
+<a id="ln-637" name="ln-637" href="#ln-637"></a><span class="w">                    </span><span class="c">!call me%grad(x,fjac)</span>
+<a id="ln-638" name="ln-638" href="#ln-638"></a><span class="w">                    </span><span class="k">select case</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="p">)</span>
+<a id="ln-639" name="ln-639" href="#ln-639"></a><span class="w">                    </span><span class="k">case</span><span class="w"> </span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
+<a id="ln-640" name="ln-640" href="#ln-640"></a><span class="w">                        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">grad</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fjac</span><span class="p">)</span>
+<a id="ln-641" name="ln-641" href="#ln-641"></a><span class="w">                    </span><span class="k">case</span><span class="w"> </span><span class="p">(</span><span class="mi">2</span><span class="p">:)</span>
+<a id="ln-642" name="ln-642" href="#ln-642"></a><span class="w">                        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">grad_sparse</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
+<a id="ln-643" name="ln-643" href="#ln-643"></a><span class="w">                    </span><span class="k">end select</span>
+<a id="ln-644" name="ln-644" href="#ln-644"></a><span class="k">                    </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
+<a id="ln-645" name="ln-645" href="#ln-645"></a><span class="w">                </span><span class="k">else</span>
+<a id="ln-646" name="ln-646" href="#ln-646"></a><span class="w">                    </span><span class="c">! and use Broyden update to estimate Jacobian</span>
+<a id="ln-647" name="ln-647" href="#ln-647"></a><span class="w">                    </span><span class="c">! for subsequent iterations.</span>
+<a id="ln-648" name="ln-648" href="#ln-648"></a>
+<a id="ln-649" name="ln-649" href="#ln-649"></a><span class="w">                    </span><span class="c">! note: fvec was computed the last iteration</span>
+<a id="ln-650" name="ln-650" href="#ln-650"></a><span class="w">                    </span><span class="n">delx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">xold</span>
+<a id="ln-651" name="ln-651" href="#ln-651"></a><span class="w">                    </span><span class="n">delf</span><span class="p">(:,</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fvec</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">prev_fvec</span>
+<a id="ln-652" name="ln-652" href="#ln-652"></a>
+<a id="ln-653" name="ln-653" href="#ln-653"></a><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="o">==</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="k">then</span><span class="w"> </span><span class="c">! dense</span>
+<a id="ln-654" name="ln-654" href="#ln-654"></a>
+<a id="ln-655" name="ln-655" href="#ln-655"></a><span class="w">                        </span><span class="n">delxmag2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">dot_product</span><span class="p">(</span><span class="n">delx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">),</span><span class="n">delx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">))</span>
+<a id="ln-656" name="ln-656" href="#ln-656"></a><span class="w">                        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">delxmag2</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">eps</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-657" name="ln-657" href="#ln-657"></a><span class="k">                            call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
+<a id="ln-658" name="ln-658" href="#ln-658"></a><span class="w">                                    </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: Divide by zero when computing Broyden update&#39;</span><span class="p">)</span>
+<a id="ln-659" name="ln-659" href="#ln-659"></a><span class="w">                            </span><span class="k">exit</span>
+<a id="ln-660" name="ln-660" href="#ln-660"></a><span class="k">                        end if</span>
+<a id="ln-661" name="ln-661" href="#ln-661"></a>
+<a id="ln-662" name="ln-662" href="#ln-662"></a><span class="w">                        </span><span class="c">! Jacobian estimate:</span>
+<a id="ln-663" name="ln-663" href="#ln-663"></a><span class="w">                        </span><span class="c">! This is the equation from wikipedia : https://en.wikipedia.org/wiki/Broyden%27s_method</span>
+<a id="ln-664" name="ln-664" href="#ln-664"></a><span class="w">                        </span><span class="n">fjac</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">prev_fjac</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="nb">matmul</span><span class="p">((</span><span class="n">delf</span><span class="o">-</span><span class="nb">matmul</span><span class="p">(</span><span class="n">prev_fjac</span><span class="p">,</span><span class="n">delx</span><span class="p">)),</span><span class="w"> </span><span class="nb">transpose</span><span class="p">(</span><span class="n">delx</span><span class="p">))</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">delxmag2</span>
+<a id="ln-665" name="ln-665" href="#ln-665"></a>
+<a id="ln-666" name="ln-666" href="#ln-666"></a><span class="w">                        </span><span class="c">! see also: eqn 4 in Schubert, which is different ...</span>
+<a id="ln-667" name="ln-667" href="#ln-667"></a>
+<a id="ln-668" name="ln-668" href="#ln-668"></a><span class="w">                    </span><span class="k">else</span><span class="w"> </span><span class="c">! using a sparse option</span>
 <a id="ln-669" name="ln-669" href="#ln-669"></a>
-<a id="ln-670" name="ln-670" href="#ln-670"></a><span class="w">            </span><span class="c">! compute the search direction p by solving linear system:</span>
-<a id="ln-671" name="ln-671" href="#ln-671"></a><span class="w">            </span><span class="n">rhs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">fvec</span><span class="w"> </span><span class="c">! RHS of the linear system</span>
-<a id="ln-672" name="ln-672" href="#ln-672"></a><span class="w">            </span><span class="k">select case</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="p">)</span>
-<a id="ln-673" name="ln-673" href="#ln-673"></a><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
-<a id="ln-674" name="ln-674" href="#ln-674"></a><span class="w">                </span><span class="c">! use dense solver</span>
-<a id="ln-675" name="ln-675" href="#ln-675"></a><span class="w">                </span><span class="k">call </span><span class="n">linear_solver</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">,</span><span class="n">fjac</span><span class="p">,</span><span class="n">rhs</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">info</span><span class="p">)</span>
-<a id="ln-676" name="ln-676" href="#ln-676"></a><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="p">(</span><span class="mi">2</span><span class="p">)</span>
-<a id="ln-677" name="ln-677" href="#ln-677"></a><span class="w">                </span><span class="c">! initialize the LSQR sparse solver</span>
-<a id="ln-678" name="ln-678" href="#ln-678"></a><span class="w">                </span><span class="k">call </span><span class="n">sparse_solver</span><span class="p">%</span><span class="n">initialize</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">irow</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="p">,&amp;</span>
-<a id="ln-679" name="ln-679" href="#ln-679"></a><span class="w">                                              </span><span class="n">atol</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">atol</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
-<a id="ln-680" name="ln-680" href="#ln-680"></a><span class="w">                                              </span><span class="n">btol</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">btol</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
-<a id="ln-681" name="ln-681" href="#ln-681"></a><span class="w">                                              </span><span class="n">conlim</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">conlim</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
-<a id="ln-682" name="ln-682" href="#ln-682"></a><span class="w">                                              </span><span class="n">itnlim</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">itnlim</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
-<a id="ln-683" name="ln-683" href="#ln-683"></a><span class="w">                                              </span><span class="n">nout</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">nout</span><span class="p">)</span>
-<a id="ln-684" name="ln-684" href="#ln-684"></a><span class="w">                </span><span class="k">call </span><span class="n">sparse_solver</span><span class="p">%</span><span class="n">solve</span><span class="p">(</span><span class="n">rhs</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">damp</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">info</span><span class="p">)</span><span class="w"> </span><span class="c">! solve the linear system</span>
-<a id="ln-685" name="ln-685" href="#ln-685"></a><span class="w">                </span><span class="c">! check convergence:</span>
-<a id="ln-686" name="ln-686" href="#ln-686"></a><span class="w">                </span><span class="k">select case</span><span class="w"> </span><span class="p">(</span><span class="n">info</span><span class="p">)</span>
-<a id="ln-687" name="ln-687" href="#ln-687"></a><span class="w">                </span><span class="k">case</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span>
-<a id="ln-688" name="ln-688" href="#ln-688"></a><span class="w">                    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">1004</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
-<a id="ln-689" name="ln-689" href="#ln-689"></a><span class="w">                                </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;LSQR Error: The system appears to be ill-conditioned. istop =&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">info</span><span class="p">)</span>
-<a id="ln-690" name="ln-690" href="#ln-690"></a><span class="w">                    </span><span class="k">exit</span>
-<a id="ln-691" name="ln-691" href="#ln-691"></a><span class="k">                case</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span>
-<a id="ln-692" name="ln-692" href="#ln-692"></a><span class="w">                    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">1005</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
-<a id="ln-693" name="ln-693" href="#ln-693"></a><span class="w">                                </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;LSQR Error: The iteration limit was reached. istop =&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">info</span><span class="p">)</span>
-<a id="ln-694" name="ln-694" href="#ln-694"></a><span class="w">                    </span><span class="k">exit</span>
-<a id="ln-695" name="ln-695" href="#ln-695"></a><span class="k">                case </span><span class="n">default</span>
-<a id="ln-696" name="ln-696" href="#ln-696"></a><span class="w">                    </span><span class="n">info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
-<a id="ln-697" name="ln-697" href="#ln-697"></a><span class="w">                </span><span class="k">end select</span>
-<a id="ln-698" name="ln-698" href="#ln-698"></a><span class="k">            case</span><span class="w"> </span><span class="p">(</span><span class="mi">3</span><span class="p">)</span>
-<a id="ln-699" name="ln-699" href="#ln-699"></a><span class="w">                </span><span class="c">! use lusol solver</span>
-<a id="ln-700" name="ln-700" href="#ln-700"></a><span class="w">                </span><span class="n">lusol_options</span><span class="p">%</span><span class="n">method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">lusol_method</span>
-<a id="ln-701" name="ln-701" href="#ln-701"></a><span class="w">                    </span><span class="c">! 0    =&gt;  TPP: Threshold Partial   Pivoting.</span>
-<a id="ln-702" name="ln-702" href="#ln-702"></a><span class="w">                    </span><span class="c">! 1    =&gt;  TRP: Threshold Rook      Pivoting.</span>
-<a id="ln-703" name="ln-703" href="#ln-703"></a><span class="w">                    </span><span class="c">! 2    =&gt;  TCP: Threshold Complete  Pivoting.</span>
-<a id="ln-704" name="ln-704" href="#ln-704"></a><span class="w">                </span><span class="k">call </span><span class="n">solve</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n_nonzeros</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">irow</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">,</span><span class="n">rhs</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">info</span><span class="p">,&amp;</span>
-<a id="ln-705" name="ln-705" href="#ln-705"></a><span class="w">                            </span><span class="n">settings</span><span class="o">=</span><span class="n">lusol_options</span><span class="p">)</span>
-<a id="ln-706" name="ln-706" href="#ln-706"></a><span class="w">            </span><span class="k">end select</span>
-<a id="ln-707" name="ln-707" href="#ln-707"></a>
-<a id="ln-708" name="ln-708" href="#ln-708"></a><span class="w">            </span><span class="c">! check for errors:</span>
-<a id="ln-709" name="ln-709" href="#ln-709"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">info</span><span class="w"> </span><span class="o">/=</span><span class="w"> </span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-710" name="ln-710" href="#ln-710"></a>
-<a id="ln-711" name="ln-711" href="#ln-711"></a><span class="k">                call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">6</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error solving linear system. info =&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">info</span><span class="p">)</span>
-<a id="ln-712" name="ln-712" href="#ln-712"></a><span class="w">                </span><span class="k">exit</span>
-<a id="ln-713" name="ln-713" href="#ln-713"></a>
-<a id="ln-714" name="ln-714" href="#ln-714"></a><span class="k">            else</span>
+<a id="ln-670" name="ln-670" href="#ln-670"></a><span class="w">                        </span><span class="c">! Just a row-by-row version of the fjac equation above.</span>
+<a id="ln-671" name="ln-671" href="#ln-671"></a><span class="w">                        </span><span class="c">! see L.K. Schubert, 1970</span>
+<a id="ln-672" name="ln-672" href="#ln-672"></a><span class="w">                        </span><span class="k">do </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">m</span>
+<a id="ln-673" name="ln-673" href="#ln-673"></a>
+<a id="ln-674" name="ln-674" href="#ln-674"></a><span class="w">                            </span><span class="n">idx</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">pack</span><span class="p">(</span><span class="n">index_array</span><span class="p">,</span><span class="w"> </span><span class="n">mask</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">irow</span><span class="o">==</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="c">! the nonzero elements in this row</span>
+<a id="ln-675" name="ln-675" href="#ln-675"></a><span class="w">                            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">size</span><span class="p">(</span><span class="n">idx</span><span class="p">)</span><span class="o">==</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">cycle</span><span class="w"> </span><span class="c">! no non-zeros in this row</span>
+<a id="ln-676" name="ln-676" href="#ln-676"></a>
+<a id="ln-677" name="ln-677" href="#ln-677"></a><span class="w">                            </span><span class="k">associate</span><span class="w"> </span><span class="p">(</span><span class="n">dx</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">delx</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="p">(</span><span class="n">idx</span><span class="p">),:))</span><span class="w"> </span><span class="c">! nonzero x vec for this row</span>
+<a id="ln-678" name="ln-678" href="#ln-678"></a><span class="w">                                </span><span class="n">delxmag2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">dot_product</span><span class="p">(</span><span class="n">dx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">),</span><span class="n">dx</span><span class="p">(:,</span><span class="mi">1</span><span class="p">))</span><span class="w"> </span><span class="c">! only those x&#39;s for this row</span>
+<a id="ln-679" name="ln-679" href="#ln-679"></a><span class="w">                                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">delxmag2</span><span class="w"> </span><span class="o">&lt;</span><span class="w"> </span><span class="n">eps</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-680" name="ln-680" href="#ln-680"></a><span class="k">                                    write</span><span class="p">(</span><span class="n">i_str</span><span class="p">,</span><span class="s1">&#39;(I10)&#39;</span><span class="p">)</span><span class="w"> </span><span class="n">i</span>
+<a id="ln-681" name="ln-681" href="#ln-681"></a><span class="w">                                    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
+<a id="ln-682" name="ln-682" href="#ln-682"></a><span class="w">                                            </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: Divide by zero when computing sparse Broyden update for row &#39;</span><span class="o">//</span><span class="p">&amp;</span>
+<a id="ln-683" name="ln-683" href="#ln-683"></a><span class="w">                                            </span><span class="nb">trim</span><span class="p">(</span><span class="nb">adjustl</span><span class="p">(</span><span class="n">i_str</span><span class="p">)))</span>
+<a id="ln-684" name="ln-684" href="#ln-684"></a><span class="w">                                    </span><span class="k">exit</span>
+<a id="ln-685" name="ln-685" href="#ln-685"></a><span class="k">                                end if</span>
+<a id="ln-686" name="ln-686" href="#ln-686"></a><span class="k">                                </span><span class="n">fjac_sparse</span><span class="p">(</span><span class="n">idx</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">prev_fjac_sparse</span><span class="p">(</span><span class="n">idx</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="p">&amp;</span>
+<a id="ln-687" name="ln-687" href="#ln-687"></a><span class="w">                                        </span><span class="nb">matmul</span><span class="p">((</span><span class="n">delf</span><span class="p">(</span><span class="n">i</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span><span class="o">-</span><span class="nb">matmul</span><span class="p">(</span><span class="n">prev_fjac_sparse</span><span class="p">(</span><span class="n">idx</span><span class="p">),</span><span class="n">dx</span><span class="p">)),</span><span class="w"> </span><span class="nb">transpose</span><span class="p">(</span><span class="n">dx</span><span class="p">))</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="n">delxmag2</span>
+<a id="ln-688" name="ln-688" href="#ln-688"></a><span class="w">                            </span><span class="k">end associate</span>
+<a id="ln-689" name="ln-689" href="#ln-689"></a>
+<a id="ln-690" name="ln-690" href="#ln-690"></a><span class="k">                        end do</span>
+<a id="ln-691" name="ln-691" href="#ln-691"></a>
+<a id="ln-692" name="ln-692" href="#ln-692"></a><span class="k">                    end if</span>
+<a id="ln-693" name="ln-693" href="#ln-693"></a><span class="k">                    </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span>
+<a id="ln-694" name="ln-694" href="#ln-694"></a><span class="w">                </span><span class="k">end if</span>
+<a id="ln-695" name="ln-695" href="#ln-695"></a><span class="k">                </span><span class="n">prev_fvec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fvec</span>
+<a id="ln-696" name="ln-696" href="#ln-696"></a><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="o">==</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-697" name="ln-697" href="#ln-697"></a><span class="k">                    </span><span class="n">prev_fjac</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fjac</span>
+<a id="ln-698" name="ln-698" href="#ln-698"></a><span class="w">                </span><span class="k">else</span>
+<a id="ln-699" name="ln-699" href="#ln-699"></a><span class="k">                    </span><span class="n">prev_fjac_sparse</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fjac_sparse</span>
+<a id="ln-700" name="ln-700" href="#ln-700"></a><span class="w">                </span><span class="k">end if</span>
+<a id="ln-701" name="ln-701" href="#ln-701"></a><span class="k">            else</span>
+<a id="ln-702" name="ln-702" href="#ln-702"></a><span class="w">                </span><span class="c">! compute the jacobian:</span>
+<a id="ln-703" name="ln-703" href="#ln-703"></a><span class="w">                </span><span class="k">select case</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="p">)</span>
+<a id="ln-704" name="ln-704" href="#ln-704"></a><span class="w">                </span><span class="k">case</span><span class="w"> </span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
+<a id="ln-705" name="ln-705" href="#ln-705"></a><span class="w">                    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">grad</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fjac</span><span class="p">)</span>
+<a id="ln-706" name="ln-706" href="#ln-706"></a><span class="w">                </span><span class="k">case</span><span class="w"> </span><span class="p">(</span><span class="mi">2</span><span class="p">:)</span>
+<a id="ln-707" name="ln-707" href="#ln-707"></a><span class="w">                    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">grad_sparse</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
+<a id="ln-708" name="ln-708" href="#ln-708"></a><span class="w">                </span><span class="k">end select</span>
+<a id="ln-709" name="ln-709" href="#ln-709"></a><span class="k">                </span><span class="n">recompute_jac</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span><span class="w">  </span><span class="c">! for broyden</span>
+<a id="ln-710" name="ln-710" href="#ln-710"></a><span class="w">                </span><span class="n">broyden_counter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
+<a id="ln-711" name="ln-711" href="#ln-711"></a><span class="w">            </span><span class="k">end if</span>
+<a id="ln-712" name="ln-712" href="#ln-712"></a>
+<a id="ln-713" name="ln-713" href="#ln-713"></a><span class="k">            </span><span class="n">xold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">x</span>
+<a id="ln-714" name="ln-714" href="#ln-714"></a><span class="w">            </span><span class="n">fold</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">f</span>
 <a id="ln-715" name="ln-715" href="#ln-715"></a>
-<a id="ln-716" name="ln-716" href="#ln-716"></a><span class="w">                </span><span class="c">! next step, using the specified method:</span>
-<a id="ln-717" name="ln-717" href="#ln-717"></a><span class="w">                </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">linesearch</span><span class="p">(</span><span class="n">xold</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">fjac</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
-<a id="ln-718" name="ln-718" href="#ln-718"></a>
-<a id="ln-719" name="ln-719" href="#ln-719"></a><span class="w">                </span><span class="c">! keep track of the number of steps in the &quot;uphill&quot; direction:</span>
-<a id="ln-720" name="ln-720" href="#ln-720"></a><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">f</span><span class="o">&gt;</span><span class="n">fold</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-721" name="ln-721" href="#ln-721"></a><span class="k">                    </span><span class="n">n_uphill</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n_uphill</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span>
-<a id="ln-722" name="ln-722" href="#ln-722"></a><span class="w">                </span><span class="k">else</span>
-<a id="ln-723" name="ln-723" href="#ln-723"></a><span class="k">                    </span><span class="n">n_uphill</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
-<a id="ln-724" name="ln-724" href="#ln-724"></a><span class="w">                </span><span class="k">end if</span>
-<a id="ln-725" name="ln-725" href="#ln-725"></a>
-<a id="ln-726" name="ln-726" href="#ln-726"></a><span class="w">                </span><span class="c">! check for stopping conditions</span>
-<a id="ln-727" name="ln-727" href="#ln-727"></a><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">f</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">tol</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-728" name="ln-728" href="#ln-728"></a>
-<a id="ln-729" name="ln-729" href="#ln-729"></a><span class="k">                    call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Required accuracy achieved&#39;</span><span class="p">)</span>
-<a id="ln-730" name="ln-730" href="#ln-730"></a><span class="w">                    </span><span class="k">exit</span>
-<a id="ln-731" name="ln-731" href="#ln-731"></a>
-<a id="ln-732" name="ln-732" href="#ln-732"></a><span class="k">                elseif</span><span class="w"> </span><span class="p">(</span><span class="w"> </span><span class="nb">maxval</span><span class="p">(</span><span class="nb">abs</span><span class="p">(</span><span class="n">x</span><span class="o">-</span><span class="n">xold</span><span class="p">))</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">tolx</span><span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-733" name="ln-733" href="#ln-733"></a>
-<a id="ln-734" name="ln-734" href="#ln-734"></a><span class="k">                    call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Solution cannot be improved&#39;</span><span class="p">)</span>
-<a id="ln-735" name="ln-735" href="#ln-735"></a><span class="w">                    </span><span class="k">exit</span>
-<a id="ln-736" name="ln-736" href="#ln-736"></a>
-<a id="ln-737" name="ln-737" href="#ln-737"></a><span class="k">                elseif</span><span class="w"> </span><span class="p">(</span><span class="n">iter</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">max_iter</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-738" name="ln-738" href="#ln-738"></a>
-<a id="ln-739" name="ln-739" href="#ln-739"></a><span class="k">                    call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Maximum number of iterations reached&#39;</span><span class="p">)</span>
+<a id="ln-716" name="ln-716" href="#ln-716"></a><span class="w">            </span><span class="c">! compute the search direction p by solving linear system:</span>
+<a id="ln-717" name="ln-717" href="#ln-717"></a><span class="w">            </span><span class="n">rhs</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">fvec</span><span class="w"> </span><span class="c">! RHS of the linear system</span>
+<a id="ln-718" name="ln-718" href="#ln-718"></a><span class="w">            </span><span class="k">select case</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">sparsity_mode</span><span class="p">)</span>
+<a id="ln-719" name="ln-719" href="#ln-719"></a><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
+<a id="ln-720" name="ln-720" href="#ln-720"></a><span class="w">                </span><span class="c">! use dense solver</span>
+<a id="ln-721" name="ln-721" href="#ln-721"></a><span class="w">                </span><span class="k">call </span><span class="n">linear_solver</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">,</span><span class="n">fjac</span><span class="p">,</span><span class="n">rhs</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">info</span><span class="p">)</span>
+<a id="ln-722" name="ln-722" href="#ln-722"></a><span class="w">            </span><span class="k">case</span><span class="w"> </span><span class="p">(</span><span class="mi">2</span><span class="p">)</span>
+<a id="ln-723" name="ln-723" href="#ln-723"></a><span class="w">                </span><span class="c">! initialize the LSQR sparse solver</span>
+<a id="ln-724" name="ln-724" href="#ln-724"></a><span class="w">                </span><span class="k">call </span><span class="n">sparse_solver</span><span class="p">%</span><span class="n">initialize</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">irow</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="p">,&amp;</span>
+<a id="ln-725" name="ln-725" href="#ln-725"></a><span class="w">                                              </span><span class="n">atol</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">atol</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
+<a id="ln-726" name="ln-726" href="#ln-726"></a><span class="w">                                              </span><span class="n">btol</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">btol</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
+<a id="ln-727" name="ln-727" href="#ln-727"></a><span class="w">                                              </span><span class="n">conlim</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">conlim</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
+<a id="ln-728" name="ln-728" href="#ln-728"></a><span class="w">                                              </span><span class="n">itnlim</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">itnlim</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
+<a id="ln-729" name="ln-729" href="#ln-729"></a><span class="w">                                              </span><span class="n">nout</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">nout</span><span class="p">)</span>
+<a id="ln-730" name="ln-730" href="#ln-730"></a><span class="w">                </span><span class="k">call </span><span class="n">sparse_solver</span><span class="p">%</span><span class="n">solve</span><span class="p">(</span><span class="n">rhs</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">damp</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">info</span><span class="p">)</span><span class="w"> </span><span class="c">! solve the linear system</span>
+<a id="ln-731" name="ln-731" href="#ln-731"></a><span class="w">                </span><span class="c">! check convergence:</span>
+<a id="ln-732" name="ln-732" href="#ln-732"></a><span class="w">                </span><span class="k">select case</span><span class="w"> </span><span class="p">(</span><span class="n">info</span><span class="p">)</span>
+<a id="ln-733" name="ln-733" href="#ln-733"></a><span class="w">                </span><span class="k">case</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span>
+<a id="ln-734" name="ln-734" href="#ln-734"></a><span class="w">                    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">1004</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
+<a id="ln-735" name="ln-735" href="#ln-735"></a><span class="w">                                </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;LSQR Error: The system appears to be ill-conditioned. istop =&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">info</span><span class="p">)</span>
+<a id="ln-736" name="ln-736" href="#ln-736"></a><span class="w">                    </span><span class="k">exit</span>
+<a id="ln-737" name="ln-737" href="#ln-737"></a><span class="k">                case</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span>
+<a id="ln-738" name="ln-738" href="#ln-738"></a><span class="w">                    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">1005</span><span class="p">,</span><span class="w"> </span><span class="p">&amp;</span>
+<a id="ln-739" name="ln-739" href="#ln-739"></a><span class="w">                                </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;LSQR Error: The iteration limit was reached. istop =&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">info</span><span class="p">)</span>
 <a id="ln-740" name="ln-740" href="#ln-740"></a><span class="w">                    </span><span class="k">exit</span>
-<a id="ln-741" name="ln-741" href="#ln-741"></a>
-<a id="ln-742" name="ln-742" href="#ln-742"></a><span class="k">                elseif</span><span class="w"> </span><span class="p">(</span><span class="n">n_uphill</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">n_uphill_max</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-743" name="ln-743" href="#ln-743"></a>
-<a id="ln-744" name="ln-744" href="#ln-744"></a><span class="k">                    call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Too many steps in the uphill direction&#39;</span><span class="p">)</span>
-<a id="ln-745" name="ln-745" href="#ln-745"></a><span class="w">                    </span><span class="k">exit</span>
-<a id="ln-746" name="ln-746" href="#ln-746"></a>
-<a id="ln-747" name="ln-747" href="#ln-747"></a><span class="k">                elseif</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">use_broyden</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-748" name="ln-748" href="#ln-748"></a>
-<a id="ln-749" name="ln-749" href="#ln-749"></a><span class="w">                    </span><span class="c">! If delxmag2 is too small when using broyden, just</span>
-<a id="ln-750" name="ln-750" href="#ln-750"></a><span class="w">                    </span><span class="c">! call the user-supplied jacobian function to avoid</span>
-<a id="ln-751" name="ln-751" href="#ln-751"></a><span class="w">                    </span><span class="c">! a divide by zero on the next step. This should</span>
-<a id="ln-752" name="ln-752" href="#ln-752"></a><span class="w">                    </span><span class="c">! normally only happen when the solution is almost converged.</span>
-<a id="ln-753" name="ln-753" href="#ln-753"></a><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">norm2</span><span class="p">(</span><span class="n">x</span><span class="o">-</span><span class="n">xold</span><span class="p">)</span><span class="o">**</span><span class="mi">2</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">eps</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-754" name="ln-754" href="#ln-754"></a><span class="k">                        </span><span class="n">recompute_jac</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">true</span><span class="p">.</span>
-<a id="ln-755" name="ln-755" href="#ln-755"></a><span class="w">                    </span><span class="k">else</span>
-<a id="ln-756" name="ln-756" href="#ln-756"></a><span class="k">                        if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">broyden_update_n</span><span class="o">&gt;</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-757" name="ln-757" href="#ln-757"></a><span class="w">                            </span><span class="c">! Note that we also recompute if we have taken an uphill step</span>
-<a id="ln-758" name="ln-758" href="#ln-758"></a><span class="w">                            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">broyden_counter</span><span class="o">==</span><span class="n">me</span><span class="p">%</span><span class="n">broyden_update_n</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">n_uphill</span><span class="o">&gt;</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-759" name="ln-759" href="#ln-759"></a><span class="w">                                </span><span class="c">! time to recompute the full jacobian</span>
-<a id="ln-760" name="ln-760" href="#ln-760"></a><span class="w">                                </span><span class="n">recompute_jac</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">true</span><span class="p">.</span>
-<a id="ln-761" name="ln-761" href="#ln-761"></a><span class="w">                            </span><span class="k">end if</span>
-<a id="ln-762" name="ln-762" href="#ln-762"></a><span class="k">                        end if</span>
-<a id="ln-763" name="ln-763" href="#ln-763"></a><span class="k">                    end if</span>
-<a id="ln-764" name="ln-764" href="#ln-764"></a>
-<a id="ln-765" name="ln-765" href="#ln-765"></a><span class="k">                endif</span>
-<a id="ln-766" name="ln-766" href="#ln-766"></a>
-<a id="ln-767" name="ln-767" href="#ln-767"></a><span class="k">            end if</span>
+<a id="ln-741" name="ln-741" href="#ln-741"></a><span class="k">                case </span><span class="n">default</span>
+<a id="ln-742" name="ln-742" href="#ln-742"></a><span class="w">                    </span><span class="n">info</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
+<a id="ln-743" name="ln-743" href="#ln-743"></a><span class="w">                </span><span class="k">end select</span>
+<a id="ln-744" name="ln-744" href="#ln-744"></a><span class="k">            case</span><span class="w"> </span><span class="p">(</span><span class="mi">3</span><span class="p">)</span>
+<a id="ln-745" name="ln-745" href="#ln-745"></a><span class="w">                </span><span class="c">! use lusol solver</span>
+<a id="ln-746" name="ln-746" href="#ln-746"></a><span class="w">                </span><span class="n">lusol_options</span><span class="p">%</span><span class="n">method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">lusol_method</span>
+<a id="ln-747" name="ln-747" href="#ln-747"></a><span class="w">                </span><span class="k">call </span><span class="n">solve</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n_nonzeros</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">irow</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">,</span><span class="n">rhs</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">info</span><span class="p">,&amp;</span>
+<a id="ln-748" name="ln-748" href="#ln-748"></a><span class="w">                           </span><span class="n">settings</span><span class="o">=</span><span class="n">lusol_options</span><span class="p">)</span>
+<a id="ln-749" name="ln-749" href="#ln-749"></a><span class="w">            </span><span class="k">end select</span>
+<a id="ln-750" name="ln-750" href="#ln-750"></a>
+<a id="ln-751" name="ln-751" href="#ln-751"></a><span class="w">            </span><span class="c">! check for errors:</span>
+<a id="ln-752" name="ln-752" href="#ln-752"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">info</span><span class="w"> </span><span class="o">/=</span><span class="w"> </span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-753" name="ln-753" href="#ln-753"></a>
+<a id="ln-754" name="ln-754" href="#ln-754"></a><span class="k">                call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">6</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error solving linear system. info =&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="o">=</span><span class="n">info</span><span class="p">)</span>
+<a id="ln-755" name="ln-755" href="#ln-755"></a><span class="w">                </span><span class="k">exit</span>
+<a id="ln-756" name="ln-756" href="#ln-756"></a>
+<a id="ln-757" name="ln-757" href="#ln-757"></a><span class="k">            else</span>
+<a id="ln-758" name="ln-758" href="#ln-758"></a>
+<a id="ln-759" name="ln-759" href="#ln-759"></a><span class="w">                </span><span class="c">! next step, using the specified method:</span>
+<a id="ln-760" name="ln-760" href="#ln-760"></a><span class="w">                </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">linesearch</span><span class="p">(</span><span class="n">xold</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">fjac</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
+<a id="ln-761" name="ln-761" href="#ln-761"></a>
+<a id="ln-762" name="ln-762" href="#ln-762"></a><span class="w">                </span><span class="c">! keep track of the number of steps in the &quot;uphill&quot; direction:</span>
+<a id="ln-763" name="ln-763" href="#ln-763"></a><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">f</span><span class="o">&gt;</span><span class="n">fold</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-764" name="ln-764" href="#ln-764"></a><span class="k">                    </span><span class="n">n_uphill</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n_uphill</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span>
+<a id="ln-765" name="ln-765" href="#ln-765"></a><span class="w">                </span><span class="k">else</span>
+<a id="ln-766" name="ln-766" href="#ln-766"></a><span class="k">                    </span><span class="n">n_uphill</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
+<a id="ln-767" name="ln-767" href="#ln-767"></a><span class="w">                </span><span class="k">end if</span>
 <a id="ln-768" name="ln-768" href="#ln-768"></a>
-<a id="ln-769" name="ln-769" href="#ln-769"></a><span class="k">        end do</span><span class="w">   </span><span class="c">!end of iterations loop</span>
-<a id="ln-770" name="ln-770" href="#ln-770"></a>
-<a id="ln-771" name="ln-771" href="#ln-771"></a><span class="w">    </span><span class="k">end if</span>
-<a id="ln-772" name="ln-772" href="#ln-772"></a>
-<a id="ln-773" name="ln-773" href="#ln-773"></a><span class="w">    </span><span class="c">!Export the last iteration:</span>
-<a id="ln-774" name="ln-774" href="#ln-774"></a><span class="w">    </span><span class="n">iter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">iter</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span>
-<a id="ln-775" name="ln-775" href="#ln-775"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">associated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">export_iteration</span><span class="p">))</span><span class="w"> </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">export_iteration</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">iter</span><span class="p">)</span>
+<a id="ln-769" name="ln-769" href="#ln-769"></a><span class="w">                </span><span class="c">! check for stopping conditions</span>
+<a id="ln-770" name="ln-770" href="#ln-770"></a><span class="w">                </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">f</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">tol</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-771" name="ln-771" href="#ln-771"></a>
+<a id="ln-772" name="ln-772" href="#ln-772"></a><span class="k">                    call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Required accuracy achieved&#39;</span><span class="p">)</span>
+<a id="ln-773" name="ln-773" href="#ln-773"></a><span class="w">                    </span><span class="k">exit</span>
+<a id="ln-774" name="ln-774" href="#ln-774"></a>
+<a id="ln-775" name="ln-775" href="#ln-775"></a><span class="k">                elseif</span><span class="w"> </span><span class="p">(</span><span class="w"> </span><span class="nb">maxval</span><span class="p">(</span><span class="nb">abs</span><span class="p">(</span><span class="n">x</span><span class="o">-</span><span class="n">xold</span><span class="p">))</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">tolx</span><span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
 <a id="ln-776" name="ln-776" href="#ln-776"></a>
-<a id="ln-777" name="ln-777" href="#ln-777"></a><span class="w">    </span><span class="k">end subroutine </span><span class="n">nlesolver_solver</span>
-<a id="ln-778" name="ln-778" href="#ln-778"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-777" name="ln-777" href="#ln-777"></a><span class="k">                    call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Solution cannot be improved&#39;</span><span class="p">)</span>
+<a id="ln-778" name="ln-778" href="#ln-778"></a><span class="w">                    </span><span class="k">exit</span>
 <a id="ln-779" name="ln-779" href="#ln-779"></a>
-<a id="ln-780" name="ln-780" href="#ln-780"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-781" name="ln-781" href="#ln-781"></a><span class="c">!&gt;</span>
-<a id="ln-782" name="ln-782" href="#ln-782"></a><span class="c">!   Destructor</span>
-<a id="ln-783" name="ln-783" href="#ln-783"></a>
-<a id="ln-784" name="ln-784" href="#ln-784"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">destroy_nlesolver_variables</span><span class="p">(</span><span class="n">me</span><span class="p">)</span>
-<a id="ln-785" name="ln-785" href="#ln-785"></a>
-<a id="ln-786" name="ln-786" href="#ln-786"></a><span class="w">    </span><span class="k">implicit none</span>
-<a id="ln-787" name="ln-787" href="#ln-787"></a>
-<a id="ln-788" name="ln-788" href="#ln-788"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-780" name="ln-780" href="#ln-780"></a><span class="k">                elseif</span><span class="w"> </span><span class="p">(</span><span class="n">iter</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">max_iter</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-781" name="ln-781" href="#ln-781"></a>
+<a id="ln-782" name="ln-782" href="#ln-782"></a><span class="k">                    call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Maximum number of iterations reached&#39;</span><span class="p">)</span>
+<a id="ln-783" name="ln-783" href="#ln-783"></a><span class="w">                    </span><span class="k">exit</span>
+<a id="ln-784" name="ln-784" href="#ln-784"></a>
+<a id="ln-785" name="ln-785" href="#ln-785"></a><span class="k">                elseif</span><span class="w"> </span><span class="p">(</span><span class="n">n_uphill</span><span class="w"> </span><span class="o">&gt;</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">n_uphill_max</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-786" name="ln-786" href="#ln-786"></a>
+<a id="ln-787" name="ln-787" href="#ln-787"></a><span class="k">                    call </span><span class="n">me</span><span class="p">%</span><span class="n">set_status</span><span class="p">(</span><span class="n">istat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="n">string</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Too many steps in the uphill direction&#39;</span><span class="p">)</span>
+<a id="ln-788" name="ln-788" href="#ln-788"></a><span class="w">                    </span><span class="k">exit</span>
 <a id="ln-789" name="ln-789" href="#ln-789"></a>
-<a id="ln-790" name="ln-790" href="#ln-790"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: class has not been initialized&#39;</span>
-<a id="ln-791" name="ln-791" href="#ln-791"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">istat</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">999</span>
-<a id="ln-792" name="ln-792" href="#ln-792"></a>
-<a id="ln-793" name="ln-793" href="#ln-793"></a><span class="w">    </span><span class="k">end subroutine </span><span class="n">destroy_nlesolver_variables</span>
-<a id="ln-794" name="ln-794" href="#ln-794"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-795" name="ln-795" href="#ln-795"></a>
-<a id="ln-796" name="ln-796" href="#ln-796"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-797" name="ln-797" href="#ln-797"></a><span class="c">!&gt;</span>
-<a id="ln-798" name="ln-798" href="#ln-798"></a><span class="c">!  Solve the linear system: \( Ax = b \), using a dense, direct method.</span>
-<a id="ln-799" name="ln-799" href="#ln-799"></a><span class="c">!</span>
-<a id="ln-800" name="ln-800" href="#ln-800"></a><span class="c">!  * if `n=m` : use LAPACK `dgesv` (LU decomposition)</span>
-<a id="ln-801" name="ln-801" href="#ln-801"></a><span class="c">!  * if `n/=m` : use LAPACK `dgels` (if m&gt;n uses QR factorization,</span>
-<a id="ln-802" name="ln-802" href="#ln-802"></a><span class="c">!    if m&lt;n uses LQ factorization)</span>
-<a id="ln-803" name="ln-803" href="#ln-803"></a>
-<a id="ln-804" name="ln-804" href="#ln-804"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">linear_solver</span><span class="p">(</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">,</span><span class="n">a</span><span class="p">,</span><span class="n">b</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">info</span><span class="p">)</span>
-<a id="ln-805" name="ln-805" href="#ln-805"></a>
-<a id="ln-806" name="ln-806" href="#ln-806"></a><span class="w">    </span><span class="k">implicit none</span>
+<a id="ln-790" name="ln-790" href="#ln-790"></a><span class="k">                elseif</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">use_broyden</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-791" name="ln-791" href="#ln-791"></a>
+<a id="ln-792" name="ln-792" href="#ln-792"></a><span class="w">                    </span><span class="c">! If delxmag2 is too small when using broyden, just</span>
+<a id="ln-793" name="ln-793" href="#ln-793"></a><span class="w">                    </span><span class="c">! call the user-supplied jacobian function to avoid</span>
+<a id="ln-794" name="ln-794" href="#ln-794"></a><span class="w">                    </span><span class="c">! a divide by zero on the next step. This should</span>
+<a id="ln-795" name="ln-795" href="#ln-795"></a><span class="w">                    </span><span class="c">! normally only happen when the solution is almost converged.</span>
+<a id="ln-796" name="ln-796" href="#ln-796"></a><span class="w">                    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">norm2</span><span class="p">(</span><span class="n">x</span><span class="o">-</span><span class="n">xold</span><span class="p">)</span><span class="o">**</span><span class="mi">2</span><span class="w"> </span><span class="o">&lt;=</span><span class="w"> </span><span class="n">eps</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-797" name="ln-797" href="#ln-797"></a><span class="k">                        </span><span class="n">recompute_jac</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">true</span><span class="p">.</span>
+<a id="ln-798" name="ln-798" href="#ln-798"></a><span class="w">                    </span><span class="k">else</span>
+<a id="ln-799" name="ln-799" href="#ln-799"></a><span class="k">                        if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">broyden_update_n</span><span class="o">&gt;</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-800" name="ln-800" href="#ln-800"></a><span class="w">                            </span><span class="c">! Note that we also recompute if we have taken an uphill step</span>
+<a id="ln-801" name="ln-801" href="#ln-801"></a><span class="w">                            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">broyden_counter</span><span class="o">==</span><span class="n">me</span><span class="p">%</span><span class="n">broyden_update_n</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">n_uphill</span><span class="o">&gt;</span><span class="mi">0</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-802" name="ln-802" href="#ln-802"></a><span class="w">                                </span><span class="c">! time to recompute the full jacobian</span>
+<a id="ln-803" name="ln-803" href="#ln-803"></a><span class="w">                                </span><span class="n">recompute_jac</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">true</span><span class="p">.</span>
+<a id="ln-804" name="ln-804" href="#ln-804"></a><span class="w">                            </span><span class="k">end if</span>
+<a id="ln-805" name="ln-805" href="#ln-805"></a><span class="k">                        end if</span>
+<a id="ln-806" name="ln-806" href="#ln-806"></a><span class="k">                    end if</span>
 <a id="ln-807" name="ln-807" href="#ln-807"></a>
-<a id="ln-808" name="ln-808" href="#ln-808"></a><span class="k">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">                 </span><span class="kd">::</span><span class="w"> </span><span class="n">n</span><span class="w">          </span><span class="c">!! number of columns in `a`</span>
-<a id="ln-809" name="ln-809" href="#ln-809"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">                 </span><span class="kd">::</span><span class="w"> </span><span class="n">m</span><span class="w">          </span><span class="c">!! number of rows in `a`</span>
-<a id="ln-810" name="ln-810" href="#ln-810"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">a</span><span class="w">          </span><span class="c">!! `A` matrix of the linear system</span>
-<a id="ln-811" name="ln-811" href="#ln-811"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">m</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">b</span><span class="w">          </span><span class="c">!! RHS of the linear system</span>
-<a id="ln-812" name="ln-812" href="#ln-812"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w">  </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span><span class="w">          </span><span class="c">!! the solution of the linear system.</span>
-<a id="ln-813" name="ln-813" href="#ln-813"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w">                </span><span class="kd">::</span><span class="w"> </span><span class="n">info</span><span class="w">       </span><span class="c">!! output status flag (`=0` if success)</span>
-<a id="ln-814" name="ln-814" href="#ln-814"></a>
-<a id="ln-815" name="ln-815" href="#ln-815"></a><span class="w">    </span><span class="c">! LAPACK routine interfaces:</span>
-<a id="ln-816" name="ln-816" href="#ln-816"></a><span class="w">    </span><span class="k">interface</span>
-<a id="ln-817" name="ln-817" href="#ln-817"></a><span class="k">        subroutine </span><span class="n">dgesv</span><span class="p">(</span><span class="n">n</span><span class="p">,</span><span class="n">nrhs</span><span class="p">,</span><span class="n">a</span><span class="p">,</span><span class="n">lda</span><span class="p">,</span><span class="n">ipiv</span><span class="p">,</span><span class="n">b</span><span class="p">,</span><span class="n">ldb</span><span class="p">,</span><span class="n">info</span><span class="p">)</span>
-<a id="ln-818" name="ln-818" href="#ln-818"></a><span class="w">            </span><span class="c">!! See: [?gesv](https://www.intel.com/content/www/us/en/develop/documentation/onemkl-developer-reference-fortran/top/lapack-routines/lapack-linear-equation-routines/lapack-linear-equation-driver-routines/gesv.html)</span>
-<a id="ln-819" name="ln-819" href="#ln-819"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span>
-<a id="ln-820" name="ln-820" href="#ln-820"></a><span class="w">            </span><span class="k">implicit none</span>
-<a id="ln-821" name="ln-821" href="#ln-821"></a><span class="k">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">info</span>
-<a id="ln-822" name="ln-822" href="#ln-822"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">lda</span>
-<a id="ln-823" name="ln-823" href="#ln-823"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">ldb</span>
-<a id="ln-824" name="ln-824" href="#ln-824"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">n</span>
-<a id="ln-825" name="ln-825" href="#ln-825"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">nrhs</span>
-<a id="ln-826" name="ln-826" href="#ln-826"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">ipiv</span><span class="p">(</span><span class="o">*</span><span class="p">)</span>
-<a id="ln-827" name="ln-827" href="#ln-827"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">a</span><span class="p">(</span><span class="n">lda</span><span class="p">,</span><span class="o">*</span><span class="p">)</span>
-<a id="ln-828" name="ln-828" href="#ln-828"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">b</span><span class="p">(</span><span class="n">ldb</span><span class="p">,</span><span class="o">*</span><span class="p">)</span>
-<a id="ln-829" name="ln-829" href="#ln-829"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">dgesv</span>
-<a id="ln-830" name="ln-830" href="#ln-830"></a><span class="w">        </span><span class="k">subroutine </span><span class="n">dgels</span><span class="p">(</span><span class="n">trans</span><span class="p">,</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">,</span><span class="n">nrhs</span><span class="p">,</span><span class="n">a</span><span class="p">,</span><span class="n">lda</span><span class="p">,</span><span class="n">b</span><span class="p">,</span><span class="n">ldb</span><span class="p">,</span><span class="n">work</span><span class="p">,</span><span class="n">lwork</span><span class="p">,</span><span class="n">info</span><span class="p">)</span>
-<a id="ln-831" name="ln-831" href="#ln-831"></a><span class="w">            </span><span class="c">!! See: [?gels](https://www.intel.com/content/www/us/en/develop/documentation/onemkl-developer-reference-fortran/top/lapack-routines/lapack-least-squares-and-eigenvalue-problem/lapack-least-squares-eigenvalue-problem-driver/linear-least-squares-lls-problems-lapack-driver/gels.html)</span>
-<a id="ln-832" name="ln-832" href="#ln-832"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span>
-<a id="ln-833" name="ln-833" href="#ln-833"></a><span class="w">            </span><span class="k">implicit none</span>
-<a id="ln-834" name="ln-834" href="#ln-834"></a><span class="k">            </span><span class="kt">character</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">trans</span>
-<a id="ln-835" name="ln-835" href="#ln-835"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">info</span>
-<a id="ln-836" name="ln-836" href="#ln-836"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">lda</span>
-<a id="ln-837" name="ln-837" href="#ln-837"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">ldb</span>
-<a id="ln-838" name="ln-838" href="#ln-838"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">lwork</span>
-<a id="ln-839" name="ln-839" href="#ln-839"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">m</span>
-<a id="ln-840" name="ln-840" href="#ln-840"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">n</span>
-<a id="ln-841" name="ln-841" href="#ln-841"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">nrhs</span>
-<a id="ln-842" name="ln-842" href="#ln-842"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">a</span><span class="p">(</span><span class="n">lda</span><span class="p">,</span><span class="o">*</span><span class="p">)</span>
-<a id="ln-843" name="ln-843" href="#ln-843"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">b</span><span class="p">(</span><span class="n">ldb</span><span class="p">,</span><span class="o">*</span><span class="p">)</span>
-<a id="ln-844" name="ln-844" href="#ln-844"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">work</span><span class="p">(</span><span class="o">*</span><span class="p">)</span>
-<a id="ln-845" name="ln-845" href="#ln-845"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">dgels</span>
-<a id="ln-846" name="ln-846" href="#ln-846"></a><span class="w">    </span><span class="k">end interface</span>
-<a id="ln-847" name="ln-847" href="#ln-847"></a>
-<a id="ln-848" name="ln-848" href="#ln-848"></a><span class="k">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w">    </span><span class="kd">::</span><span class="w"> </span><span class="n">ipiv</span><span class="w">   </span><span class="c">!! pivot indices array</span>
-<a id="ln-849" name="ln-849" href="#ln-849"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">bmat</span><span class="w">   </span><span class="c">!! copy of `b` so it won&#39;t be overwritten</span>
-<a id="ln-850" name="ln-850" href="#ln-850"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">work</span><span class="w">   </span><span class="c">!! work array for `dgels`</span>
-<a id="ln-851" name="ln-851" href="#ln-851"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">amat</span><span class="w">   </span><span class="c">!! copy of `a` so it won&#39;t be overwritten</span>
-<a id="ln-852" name="ln-852" href="#ln-852"></a><span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">lwork</span><span class="w">  </span><span class="c">!! size of `work`</span>
-<a id="ln-853" name="ln-853" href="#ln-853"></a>
-<a id="ln-854" name="ln-854" href="#ln-854"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">amat</span><span class="p">(</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">))</span>
-<a id="ln-855" name="ln-855" href="#ln-855"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">bmat</span><span class="p">(</span><span class="nb">max</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">),</span><span class="mi">1</span><span class="p">))</span>
-<a id="ln-856" name="ln-856" href="#ln-856"></a>
-<a id="ln-857" name="ln-857" href="#ln-857"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="o">==</span><span class="n">m</span><span class="p">)</span><span class="w"> </span><span class="k">then</span><span class="w">  </span><span class="c">!normal inverse</span>
-<a id="ln-858" name="ln-858" href="#ln-858"></a>
-<a id="ln-859" name="ln-859" href="#ln-859"></a><span class="w">        </span><span class="k">allocate</span><span class="p">(</span><span class="n">ipiv</span><span class="p">(</span><span class="n">n</span><span class="p">))</span>
-<a id="ln-860" name="ln-860" href="#ln-860"></a>
-<a id="ln-861" name="ln-861" href="#ln-861"></a><span class="w">        </span><span class="n">amat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span>
-<a id="ln-862" name="ln-862" href="#ln-862"></a><span class="w">        </span><span class="n">bmat</span><span class="p">(</span><span class="mi">1</span><span class="p">:</span><span class="n">n</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">b</span>
-<a id="ln-863" name="ln-863" href="#ln-863"></a><span class="w">        </span><span class="k">call </span><span class="n">dgesv</span><span class="p">(</span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">amat</span><span class="p">,</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="n">ipiv</span><span class="p">,</span><span class="w"> </span><span class="n">bmat</span><span class="p">,</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="n">info</span><span class="p">)</span>
-<a id="ln-864" name="ln-864" href="#ln-864"></a><span class="w">        </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bmat</span><span class="p">(</span><span class="mi">1</span><span class="p">:</span><span class="n">n</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span>
-<a id="ln-865" name="ln-865" href="#ln-865"></a>
-<a id="ln-866" name="ln-866" href="#ln-866"></a><span class="w">    </span><span class="k">else</span>
-<a id="ln-867" name="ln-867" href="#ln-867"></a>
-<a id="ln-868" name="ln-868" href="#ln-868"></a><span class="k">        </span><span class="n">amat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span>
-<a id="ln-869" name="ln-869" href="#ln-869"></a><span class="w">        </span><span class="n">bmat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">zero</span>
-<a id="ln-870" name="ln-870" href="#ln-870"></a><span class="w">        </span><span class="n">bmat</span><span class="p">(</span><span class="mi">1</span><span class="p">:</span><span class="n">m</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">b</span>
-<a id="ln-871" name="ln-871" href="#ln-871"></a><span class="w">        </span><span class="n">lwork</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">min</span><span class="p">(</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">)</span><span class="o">+</span><span class="nb">max</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">)</span>
-<a id="ln-872" name="ln-872" href="#ln-872"></a><span class="w">        </span><span class="k">allocate</span><span class="p">(</span><span class="n">work</span><span class="p">(</span><span class="n">lwork</span><span class="p">))</span>
-<a id="ln-873" name="ln-873" href="#ln-873"></a><span class="w">        </span><span class="k">call </span><span class="n">dgels</span><span class="p">(</span><span class="s1">&#39;N&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">m</span><span class="p">,</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">amat</span><span class="p">,</span><span class="w"> </span><span class="n">m</span><span class="p">,</span><span class="w"> </span><span class="n">bmat</span><span class="p">,</span><span class="w"> </span><span class="nb">max</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">),</span><span class="w"> </span><span class="n">work</span><span class="p">,</span><span class="w"> </span><span class="n">lwork</span><span class="p">,</span><span class="w"> </span><span class="n">info</span><span class="p">)</span>
-<a id="ln-874" name="ln-874" href="#ln-874"></a><span class="w">        </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bmat</span><span class="p">(</span><span class="mi">1</span><span class="p">:</span><span class="n">n</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span>
-<a id="ln-875" name="ln-875" href="#ln-875"></a>
-<a id="ln-876" name="ln-876" href="#ln-876"></a><span class="w">    </span><span class="k">end if</span>
-<a id="ln-877" name="ln-877" href="#ln-877"></a>
-<a id="ln-878" name="ln-878" href="#ln-878"></a><span class="k">    end subroutine </span><span class="n">linear_solver</span>
-<a id="ln-879" name="ln-879" href="#ln-879"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-880" name="ln-880" href="#ln-880"></a>
-<a id="ln-881" name="ln-881" href="#ln-881"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-882" name="ln-882" href="#ln-882"></a><span class="c">!&gt;</span>
-<a id="ln-883" name="ln-883" href="#ln-883"></a><span class="c">!  Take a simple step in the search direction of `p * alpha`.</span>
-<a id="ln-884" name="ln-884" href="#ln-884"></a>
-<a id="ln-885" name="ln-885" href="#ln-885"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">simple_step</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">xold</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">fjac</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
-<a id="ln-886" name="ln-886" href="#ln-886"></a>
-<a id="ln-887" name="ln-887" href="#ln-887"></a><span class="w">    </span><span class="k">implicit none</span>
-<a id="ln-888" name="ln-888" href="#ln-888"></a>
-<a id="ln-889" name="ln-889" href="#ln-889"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
-<a id="ln-890" name="ln-890" href="#ln-890"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xold</span><span class="w">      </span><span class="c">!! previous value of `x`</span>
-<a id="ln-891" name="ln-891" href="#ln-891"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">p</span><span class="w">         </span><span class="c">!! search direction</span>
-<a id="ln-892" name="ln-892" href="#ln-892"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span><span class="w">        </span><span class="c">!! new `x`</span>
-<a id="ln-893" name="ln-893" href="#ln-893"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span><span class="w">                      </span><span class="c">!! magnitude of `fvec`</span>
-<a id="ln-894" name="ln-894" href="#ln-894"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec</span><span class="w">   </span><span class="c">!! function vector</span>
-<a id="ln-895" name="ln-895" href="#ln-895"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac</span><span class="w"> </span><span class="c">!! jacobian matrix [dense]</span>
-<a id="ln-896" name="ln-896" href="#ln-896"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac_sparse</span><span class="w"> </span><span class="c">!! jacobian matrix [sparse]</span>
-<a id="ln-897" name="ln-897" href="#ln-897"></a>
-<a id="ln-898" name="ln-898" href="#ln-898"></a><span class="w">    </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">xold</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha</span>
+<a id="ln-808" name="ln-808" href="#ln-808"></a><span class="k">                endif</span>
+<a id="ln-809" name="ln-809" href="#ln-809"></a>
+<a id="ln-810" name="ln-810" href="#ln-810"></a><span class="k">            end if</span>
+<a id="ln-811" name="ln-811" href="#ln-811"></a>
+<a id="ln-812" name="ln-812" href="#ln-812"></a><span class="k">        end do</span><span class="w">   </span><span class="c">!end of iterations loop</span>
+<a id="ln-813" name="ln-813" href="#ln-813"></a>
+<a id="ln-814" name="ln-814" href="#ln-814"></a><span class="w">    </span><span class="k">end if</span>
+<a id="ln-815" name="ln-815" href="#ln-815"></a>
+<a id="ln-816" name="ln-816" href="#ln-816"></a><span class="w">    </span><span class="c">!Export the last iteration:</span>
+<a id="ln-817" name="ln-817" href="#ln-817"></a><span class="w">    </span><span class="n">iter</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">iter</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span>
+<a id="ln-818" name="ln-818" href="#ln-818"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">associated</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">export_iteration</span><span class="p">))</span><span class="w"> </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">export_iteration</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">iter</span><span class="p">)</span>
+<a id="ln-819" name="ln-819" href="#ln-819"></a>
+<a id="ln-820" name="ln-820" href="#ln-820"></a><span class="w">    </span><span class="k">end subroutine </span><span class="n">nlesolver_solver</span>
+<a id="ln-821" name="ln-821" href="#ln-821"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-822" name="ln-822" href="#ln-822"></a>
+<a id="ln-823" name="ln-823" href="#ln-823"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-824" name="ln-824" href="#ln-824"></a><span class="c">!&gt;</span>
+<a id="ln-825" name="ln-825" href="#ln-825"></a><span class="c">!   Destructor</span>
+<a id="ln-826" name="ln-826" href="#ln-826"></a>
+<a id="ln-827" name="ln-827" href="#ln-827"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">destroy_nlesolver_variables</span><span class="p">(</span><span class="n">me</span><span class="p">)</span>
+<a id="ln-828" name="ln-828" href="#ln-828"></a>
+<a id="ln-829" name="ln-829" href="#ln-829"></a><span class="w">    </span><span class="k">implicit none</span>
+<a id="ln-830" name="ln-830" href="#ln-830"></a>
+<a id="ln-831" name="ln-831" href="#ln-831"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-832" name="ln-832" href="#ln-832"></a>
+<a id="ln-833" name="ln-833" href="#ln-833"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">message</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s1">&#39;Error: class has not been initialized&#39;</span>
+<a id="ln-834" name="ln-834" href="#ln-834"></a><span class="w">    </span><span class="n">me</span><span class="p">%</span><span class="n">istat</span><span class="w">   </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="mi">999</span>
+<a id="ln-835" name="ln-835" href="#ln-835"></a>
+<a id="ln-836" name="ln-836" href="#ln-836"></a><span class="w">    </span><span class="k">end subroutine </span><span class="n">destroy_nlesolver_variables</span>
+<a id="ln-837" name="ln-837" href="#ln-837"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-838" name="ln-838" href="#ln-838"></a>
+<a id="ln-839" name="ln-839" href="#ln-839"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-840" name="ln-840" href="#ln-840"></a><span class="c">!&gt;</span>
+<a id="ln-841" name="ln-841" href="#ln-841"></a><span class="c">!  Solve the linear system: \( Ax = b \), using a dense, direct method.</span>
+<a id="ln-842" name="ln-842" href="#ln-842"></a><span class="c">!</span>
+<a id="ln-843" name="ln-843" href="#ln-843"></a><span class="c">!  * if `n=m` : use LAPACK `dgesv` (LU decomposition)</span>
+<a id="ln-844" name="ln-844" href="#ln-844"></a><span class="c">!  * if `n/=m` : use LAPACK `dgels` (if m&gt;n uses QR factorization,</span>
+<a id="ln-845" name="ln-845" href="#ln-845"></a><span class="c">!    if m&lt;n uses LQ factorization)</span>
+<a id="ln-846" name="ln-846" href="#ln-846"></a>
+<a id="ln-847" name="ln-847" href="#ln-847"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">linear_solver</span><span class="p">(</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">,</span><span class="n">a</span><span class="p">,</span><span class="n">b</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">info</span><span class="p">)</span>
+<a id="ln-848" name="ln-848" href="#ln-848"></a>
+<a id="ln-849" name="ln-849" href="#ln-849"></a><span class="w">    </span><span class="k">implicit none</span>
+<a id="ln-850" name="ln-850" href="#ln-850"></a>
+<a id="ln-851" name="ln-851" href="#ln-851"></a><span class="k">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">                 </span><span class="kd">::</span><span class="w"> </span><span class="n">n</span><span class="w">          </span><span class="c">!! number of columns in `a`</span>
+<a id="ln-852" name="ln-852" href="#ln-852"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">                 </span><span class="kd">::</span><span class="w"> </span><span class="n">m</span><span class="w">          </span><span class="c">!! number of rows in `a`</span>
+<a id="ln-853" name="ln-853" href="#ln-853"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">a</span><span class="w">          </span><span class="c">!! `A` matrix of the linear system</span>
+<a id="ln-854" name="ln-854" href="#ln-854"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">m</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">b</span><span class="w">          </span><span class="c">!! RHS of the linear system</span>
+<a id="ln-855" name="ln-855" href="#ln-855"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w">  </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span><span class="w">          </span><span class="c">!! the solution of the linear system.</span>
+<a id="ln-856" name="ln-856" href="#ln-856"></a><span class="w">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w">                </span><span class="kd">::</span><span class="w"> </span><span class="n">info</span><span class="w">       </span><span class="c">!! output status flag (`=0` if success)</span>
+<a id="ln-857" name="ln-857" href="#ln-857"></a>
+<a id="ln-858" name="ln-858" href="#ln-858"></a><span class="w">    </span><span class="c">! LAPACK routine interfaces:</span>
+<a id="ln-859" name="ln-859" href="#ln-859"></a><span class="w">    </span><span class="k">interface</span>
+<a id="ln-860" name="ln-860" href="#ln-860"></a><span class="k">        subroutine </span><span class="n">dgesv</span><span class="p">(</span><span class="n">n</span><span class="p">,</span><span class="n">nrhs</span><span class="p">,</span><span class="n">a</span><span class="p">,</span><span class="n">lda</span><span class="p">,</span><span class="n">ipiv</span><span class="p">,</span><span class="n">b</span><span class="p">,</span><span class="n">ldb</span><span class="p">,</span><span class="n">info</span><span class="p">)</span>
+<a id="ln-861" name="ln-861" href="#ln-861"></a><span class="w">            </span><span class="c">!! See: [?gesv](https://www.intel.com/content/www/us/en/develop/documentation/onemkl-developer-reference-fortran/top/lapack-routines/lapack-linear-equation-routines/lapack-linear-equation-driver-routines/gesv.html)</span>
+<a id="ln-862" name="ln-862" href="#ln-862"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span>
+<a id="ln-863" name="ln-863" href="#ln-863"></a><span class="w">            </span><span class="k">implicit none</span>
+<a id="ln-864" name="ln-864" href="#ln-864"></a><span class="k">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">info</span>
+<a id="ln-865" name="ln-865" href="#ln-865"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">lda</span>
+<a id="ln-866" name="ln-866" href="#ln-866"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">ldb</span>
+<a id="ln-867" name="ln-867" href="#ln-867"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">n</span>
+<a id="ln-868" name="ln-868" href="#ln-868"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">nrhs</span>
+<a id="ln-869" name="ln-869" href="#ln-869"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">ipiv</span><span class="p">(</span><span class="o">*</span><span class="p">)</span>
+<a id="ln-870" name="ln-870" href="#ln-870"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">a</span><span class="p">(</span><span class="n">lda</span><span class="p">,</span><span class="o">*</span><span class="p">)</span>
+<a id="ln-871" name="ln-871" href="#ln-871"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">b</span><span class="p">(</span><span class="n">ldb</span><span class="p">,</span><span class="o">*</span><span class="p">)</span>
+<a id="ln-872" name="ln-872" href="#ln-872"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">dgesv</span>
+<a id="ln-873" name="ln-873" href="#ln-873"></a><span class="w">        </span><span class="k">subroutine </span><span class="n">dgels</span><span class="p">(</span><span class="n">trans</span><span class="p">,</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">,</span><span class="n">nrhs</span><span class="p">,</span><span class="n">a</span><span class="p">,</span><span class="n">lda</span><span class="p">,</span><span class="n">b</span><span class="p">,</span><span class="n">ldb</span><span class="p">,</span><span class="n">work</span><span class="p">,</span><span class="n">lwork</span><span class="p">,</span><span class="n">info</span><span class="p">)</span>
+<a id="ln-874" name="ln-874" href="#ln-874"></a><span class="w">            </span><span class="c">!! See: [?gels](https://www.intel.com/content/www/us/en/develop/documentation/onemkl-developer-reference-fortran/top/lapack-routines/lapack-least-squares-and-eigenvalue-problem/lapack-least-squares-eigenvalue-problem-driver/linear-least-squares-lls-problems-lapack-driver/gels.html)</span>
+<a id="ln-875" name="ln-875" href="#ln-875"></a><span class="w">            </span><span class="k">import</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">wp</span>
+<a id="ln-876" name="ln-876" href="#ln-876"></a><span class="w">            </span><span class="k">implicit none</span>
+<a id="ln-877" name="ln-877" href="#ln-877"></a><span class="k">            </span><span class="kt">character</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">trans</span>
+<a id="ln-878" name="ln-878" href="#ln-878"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">info</span>
+<a id="ln-879" name="ln-879" href="#ln-879"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">lda</span>
+<a id="ln-880" name="ln-880" href="#ln-880"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">ldb</span>
+<a id="ln-881" name="ln-881" href="#ln-881"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">lwork</span>
+<a id="ln-882" name="ln-882" href="#ln-882"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">m</span>
+<a id="ln-883" name="ln-883" href="#ln-883"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">n</span>
+<a id="ln-884" name="ln-884" href="#ln-884"></a><span class="w">            </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">nrhs</span>
+<a id="ln-885" name="ln-885" href="#ln-885"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">a</span><span class="p">(</span><span class="n">lda</span><span class="p">,</span><span class="o">*</span><span class="p">)</span>
+<a id="ln-886" name="ln-886" href="#ln-886"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">b</span><span class="p">(</span><span class="n">ldb</span><span class="p">,</span><span class="o">*</span><span class="p">)</span>
+<a id="ln-887" name="ln-887" href="#ln-887"></a><span class="w">            </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">work</span><span class="p">(</span><span class="o">*</span><span class="p">)</span>
+<a id="ln-888" name="ln-888" href="#ln-888"></a><span class="w">        </span><span class="k">end subroutine </span><span class="n">dgels</span>
+<a id="ln-889" name="ln-889" href="#ln-889"></a><span class="w">    </span><span class="k">end interface</span>
+<a id="ln-890" name="ln-890" href="#ln-890"></a>
+<a id="ln-891" name="ln-891" href="#ln-891"></a><span class="k">    </span><span class="kt">integer</span><span class="p">,</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w">    </span><span class="kd">::</span><span class="w"> </span><span class="n">ipiv</span><span class="w">   </span><span class="c">!! pivot indices array</span>
+<a id="ln-892" name="ln-892" href="#ln-892"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">bmat</span><span class="w">   </span><span class="c">!! copy of `b` so it won&#39;t be overwritten</span>
+<a id="ln-893" name="ln-893" href="#ln-893"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">work</span><span class="w">   </span><span class="c">!! work array for `dgels`</span>
+<a id="ln-894" name="ln-894" href="#ln-894"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">amat</span><span class="w">   </span><span class="c">!! copy of `a` so it won&#39;t be overwritten</span>
+<a id="ln-895" name="ln-895" href="#ln-895"></a><span class="w">    </span><span class="kt">integer</span><span class="w">                             </span><span class="kd">::</span><span class="w"> </span><span class="n">lwork</span><span class="w">  </span><span class="c">!! size of `work`</span>
+<a id="ln-896" name="ln-896" href="#ln-896"></a>
+<a id="ln-897" name="ln-897" href="#ln-897"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">amat</span><span class="p">(</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">))</span>
+<a id="ln-898" name="ln-898" href="#ln-898"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">bmat</span><span class="p">(</span><span class="nb">max</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">),</span><span class="mi">1</span><span class="p">))</span>
 <a id="ln-899" name="ln-899" href="#ln-899"></a>
-<a id="ln-900" name="ln-900" href="#ln-900"></a><span class="w">    </span><span class="c">!evaluate the function at the new point:</span>
-<a id="ln-901" name="ln-901" href="#ln-901"></a><span class="w">    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fvec</span><span class="p">)</span>
-<a id="ln-902" name="ln-902" href="#ln-902"></a><span class="w">    </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">norm2</span><span class="p">(</span><span class="n">fvec</span><span class="p">)</span>
+<a id="ln-900" name="ln-900" href="#ln-900"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">n</span><span class="o">==</span><span class="n">m</span><span class="p">)</span><span class="w"> </span><span class="k">then</span><span class="w">  </span><span class="c">!normal inverse</span>
+<a id="ln-901" name="ln-901" href="#ln-901"></a>
+<a id="ln-902" name="ln-902" href="#ln-902"></a><span class="w">        </span><span class="k">allocate</span><span class="p">(</span><span class="n">ipiv</span><span class="p">(</span><span class="n">n</span><span class="p">))</span>
 <a id="ln-903" name="ln-903" href="#ln-903"></a>
-<a id="ln-904" name="ln-904" href="#ln-904"></a><span class="w">    </span><span class="k">end subroutine </span><span class="n">simple_step</span>
-<a id="ln-905" name="ln-905" href="#ln-905"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-906" name="ln-906" href="#ln-906"></a>
-<a id="ln-907" name="ln-907" href="#ln-907"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-908" name="ln-908" href="#ln-908"></a><span class="c">!&gt;</span>
-<a id="ln-909" name="ln-909" href="#ln-909"></a><span class="c">!  Backtracking line search.</span>
-<a id="ln-910" name="ln-910" href="#ln-910"></a><span class="c">!</span>
-<a id="ln-911" name="ln-911" href="#ln-911"></a><span class="c">!### See also</span>
-<a id="ln-912" name="ln-912" href="#ln-912"></a><span class="c">!  * [Backtracking line search](https://en.wikipedia.org/wiki/Backtracking_line_search)</span>
-<a id="ln-913" name="ln-913" href="#ln-913"></a><span class="c">!</span>
-<a id="ln-914" name="ln-914" href="#ln-914"></a><span class="c">!@note Either `fjac` or `fjac_sparse` should be present.</span>
-<a id="ln-915" name="ln-915" href="#ln-915"></a>
-<a id="ln-916" name="ln-916" href="#ln-916"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">backtracking_linesearch</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">xold</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">fjac</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
-<a id="ln-917" name="ln-917" href="#ln-917"></a>
-<a id="ln-918" name="ln-918" href="#ln-918"></a><span class="w">    </span><span class="k">implicit none</span>
-<a id="ln-919" name="ln-919" href="#ln-919"></a>
-<a id="ln-920" name="ln-920" href="#ln-920"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
-<a id="ln-921" name="ln-921" href="#ln-921"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xold</span><span class="w">      </span><span class="c">!! previous value of `x`</span>
-<a id="ln-922" name="ln-922" href="#ln-922"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">p</span><span class="w">         </span><span class="c">!! search direction</span>
-<a id="ln-923" name="ln-923" href="#ln-923"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span><span class="w">        </span><span class="c">!! new `x`</span>
-<a id="ln-924" name="ln-924" href="#ln-924"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span><span class="w">                      </span><span class="c">!! magnitude of `fvec`</span>
-<a id="ln-925" name="ln-925" href="#ln-925"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec</span><span class="w">   </span><span class="c">!! function vector</span>
-<a id="ln-926" name="ln-926" href="#ln-926"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac</span><span class="w"> </span><span class="c">!! jacobian matrix [dense]</span>
-<a id="ln-927" name="ln-927" href="#ln-927"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac_sparse</span><span class="w"> </span><span class="c">!! jacobian matrix [sparse]</span>
-<a id="ln-928" name="ln-928" href="#ln-928"></a>
-<a id="ln-929" name="ln-929" href="#ln-929"></a><span class="w">    </span><span class="kt">integer</span><span class="w">    </span><span class="kd">::</span><span class="w"> </span><span class="n">i</span><span class="w">                  </span><span class="c">!! counter</span>
-<a id="ln-930" name="ln-930" href="#ln-930"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">slope</span><span class="w">              </span><span class="c">!! local slope of the function of `alpha` along the search direction used for line search</span>
-<a id="ln-931" name="ln-931" href="#ln-931"></a><span class="w">    </span><span class="kt">logical</span><span class="w">    </span><span class="kd">::</span><span class="w"> </span><span class="n">min_alpha_reached</span><span class="w">  </span><span class="c">!! if the minimum step size is reached during the line search</span>
-<a id="ln-932" name="ln-932" href="#ln-932"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">alpha</span><span class="w">              </span><span class="c">!! `alpha` for the line search</span>
-<a id="ln-933" name="ln-933" href="#ln-933"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">ftmp</span><span class="w">               </span><span class="c">!! `f` value for linesearch</span>
-<a id="ln-934" name="ln-934" href="#ln-934"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">t</span><span class="w">                  </span><span class="c">!! used for line search</span>
-<a id="ln-935" name="ln-935" href="#ln-935"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">gradf</span><span class="w">      </span><span class="c">!! line search objective function gradient vector</span>
-<a id="ln-936" name="ln-936" href="#ln-936"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xtmp</span><span class="w">       </span><span class="c">!! `x` value for linesearch</span>
-<a id="ln-937" name="ln-937" href="#ln-937"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvectmp</span><span class="w">    </span><span class="c">!! `fvec` value for linesearch</span>
-<a id="ln-938" name="ln-938" href="#ln-938"></a>
-<a id="ln-939" name="ln-939" href="#ln-939"></a><span class="w">    </span><span class="c">! allocate arrays:</span>
-<a id="ln-940" name="ln-940" href="#ln-940"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">gradf</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">))</span>
-<a id="ln-941" name="ln-941" href="#ln-941"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">xtmp</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">))</span>
-<a id="ln-942" name="ln-942" href="#ln-942"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">fvectmp</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">))</span>
-<a id="ln-943" name="ln-943" href="#ln-943"></a>
-<a id="ln-944" name="ln-944" href="#ln-944"></a><span class="w">    </span><span class="c">! compute the gradient of the function to be minimized</span>
-<a id="ln-945" name="ln-945" href="#ln-945"></a><span class="w">    </span><span class="c">! (which in this case is 1/2 the norm of fvec). Use the chain</span>
-<a id="ln-946" name="ln-946" href="#ln-946"></a><span class="w">    </span><span class="c">! rule and the Jacobian matrix already computed.</span>
-<a id="ln-947" name="ln-947" href="#ln-947"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">fjac</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-948" name="ln-948" href="#ln-948"></a><span class="w">        </span><span class="c">! dense</span>
-<a id="ln-949" name="ln-949" href="#ln-949"></a><span class="w">        </span><span class="k">do </span><span class="n">i</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n</span>
-<a id="ln-950" name="ln-950" href="#ln-950"></a><span class="w">            </span><span class="n">gradf</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">dot_product</span><span class="p">(</span><span class="n">fvec</span><span class="p">,</span><span class="n">fjac</span><span class="p">(:,</span><span class="n">i</span><span class="p">))</span>
-<a id="ln-951" name="ln-951" href="#ln-951"></a><span class="w">        </span><span class="k">end do</span>
-<a id="ln-952" name="ln-952" href="#ln-952"></a><span class="k">    else</span>
-<a id="ln-953" name="ln-953" href="#ln-953"></a><span class="w">        </span><span class="c">! sparse</span>
-<a id="ln-954" name="ln-954" href="#ln-954"></a><span class="w">        </span><span class="k">do </span><span class="n">i</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n</span>
-<a id="ln-955" name="ln-955" href="#ln-955"></a><span class="w">            </span><span class="n">gradf</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">dot_product</span><span class="p">(</span><span class="n">fvec</span><span class="p">,</span><span class="nb">pack</span><span class="p">(</span><span class="n">fjac_sparse</span><span class="p">,</span><span class="n">mask</span><span class="o">=</span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="o">==</span><span class="n">i</span><span class="p">))</span>
-<a id="ln-956" name="ln-956" href="#ln-956"></a><span class="w">        </span><span class="k">end do</span>
-<a id="ln-957" name="ln-957" href="#ln-957"></a><span class="k">    end if</span>
-<a id="ln-958" name="ln-958" href="#ln-958"></a><span class="k">    </span><span class="n">slope</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">dot_product</span><span class="p">(</span><span class="n">p</span><span class="p">,</span><span class="w"> </span><span class="n">gradf</span><span class="p">)</span>
-<a id="ln-959" name="ln-959" href="#ln-959"></a><span class="w">    </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">me</span><span class="p">%</span><span class="n">c</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">slope</span>
+<a id="ln-904" name="ln-904" href="#ln-904"></a><span class="w">        </span><span class="n">amat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span>
+<a id="ln-905" name="ln-905" href="#ln-905"></a><span class="w">        </span><span class="n">bmat</span><span class="p">(</span><span class="mi">1</span><span class="p">:</span><span class="n">n</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">b</span>
+<a id="ln-906" name="ln-906" href="#ln-906"></a><span class="w">        </span><span class="k">call </span><span class="n">dgesv</span><span class="p">(</span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">amat</span><span class="p">,</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="n">ipiv</span><span class="p">,</span><span class="w"> </span><span class="n">bmat</span><span class="p">,</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="n">info</span><span class="p">)</span>
+<a id="ln-907" name="ln-907" href="#ln-907"></a><span class="w">        </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bmat</span><span class="p">(</span><span class="mi">1</span><span class="p">:</span><span class="n">n</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span>
+<a id="ln-908" name="ln-908" href="#ln-908"></a>
+<a id="ln-909" name="ln-909" href="#ln-909"></a><span class="w">    </span><span class="k">else</span>
+<a id="ln-910" name="ln-910" href="#ln-910"></a>
+<a id="ln-911" name="ln-911" href="#ln-911"></a><span class="k">        </span><span class="n">amat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">a</span>
+<a id="ln-912" name="ln-912" href="#ln-912"></a><span class="w">        </span><span class="n">bmat</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">zero</span>
+<a id="ln-913" name="ln-913" href="#ln-913"></a><span class="w">        </span><span class="n">bmat</span><span class="p">(</span><span class="mi">1</span><span class="p">:</span><span class="n">m</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">b</span>
+<a id="ln-914" name="ln-914" href="#ln-914"></a><span class="w">        </span><span class="n">lwork</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">min</span><span class="p">(</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">)</span><span class="o">+</span><span class="nb">max</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">)</span>
+<a id="ln-915" name="ln-915" href="#ln-915"></a><span class="w">        </span><span class="k">allocate</span><span class="p">(</span><span class="n">work</span><span class="p">(</span><span class="n">lwork</span><span class="p">))</span>
+<a id="ln-916" name="ln-916" href="#ln-916"></a><span class="w">        </span><span class="k">call </span><span class="n">dgels</span><span class="p">(</span><span class="s1">&#39;N&#39;</span><span class="p">,</span><span class="w"> </span><span class="n">m</span><span class="p">,</span><span class="w"> </span><span class="n">n</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">amat</span><span class="p">,</span><span class="w"> </span><span class="n">m</span><span class="p">,</span><span class="w"> </span><span class="n">bmat</span><span class="p">,</span><span class="w"> </span><span class="nb">max</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="n">m</span><span class="p">,</span><span class="n">n</span><span class="p">),</span><span class="w"> </span><span class="n">work</span><span class="p">,</span><span class="w"> </span><span class="n">lwork</span><span class="p">,</span><span class="w"> </span><span class="n">info</span><span class="p">)</span>
+<a id="ln-917" name="ln-917" href="#ln-917"></a><span class="w">        </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">bmat</span><span class="p">(</span><span class="mi">1</span><span class="p">:</span><span class="n">n</span><span class="p">,</span><span class="mi">1</span><span class="p">)</span>
+<a id="ln-918" name="ln-918" href="#ln-918"></a>
+<a id="ln-919" name="ln-919" href="#ln-919"></a><span class="w">    </span><span class="k">end if</span>
+<a id="ln-920" name="ln-920" href="#ln-920"></a>
+<a id="ln-921" name="ln-921" href="#ln-921"></a><span class="k">    end subroutine </span><span class="n">linear_solver</span>
+<a id="ln-922" name="ln-922" href="#ln-922"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-923" name="ln-923" href="#ln-923"></a>
+<a id="ln-924" name="ln-924" href="#ln-924"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-925" name="ln-925" href="#ln-925"></a><span class="c">!&gt;</span>
+<a id="ln-926" name="ln-926" href="#ln-926"></a><span class="c">!  Take a simple step in the search direction of `p * alpha`.</span>
+<a id="ln-927" name="ln-927" href="#ln-927"></a>
+<a id="ln-928" name="ln-928" href="#ln-928"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">simple_step</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">xold</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">fjac</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
+<a id="ln-929" name="ln-929" href="#ln-929"></a>
+<a id="ln-930" name="ln-930" href="#ln-930"></a><span class="w">    </span><span class="k">implicit none</span>
+<a id="ln-931" name="ln-931" href="#ln-931"></a>
+<a id="ln-932" name="ln-932" href="#ln-932"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-933" name="ln-933" href="#ln-933"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xold</span><span class="w">      </span><span class="c">!! previous value of `x`</span>
+<a id="ln-934" name="ln-934" href="#ln-934"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">p</span><span class="w">         </span><span class="c">!! search direction</span>
+<a id="ln-935" name="ln-935" href="#ln-935"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span><span class="w">        </span><span class="c">!! new `x`</span>
+<a id="ln-936" name="ln-936" href="#ln-936"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span><span class="w">                      </span><span class="c">!! magnitude of `fvec`</span>
+<a id="ln-937" name="ln-937" href="#ln-937"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec</span><span class="w">   </span><span class="c">!! function vector</span>
+<a id="ln-938" name="ln-938" href="#ln-938"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac</span><span class="w"> </span><span class="c">!! jacobian matrix [dense]</span>
+<a id="ln-939" name="ln-939" href="#ln-939"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac_sparse</span><span class="w"> </span><span class="c">!! jacobian matrix [sparse]</span>
+<a id="ln-940" name="ln-940" href="#ln-940"></a>
+<a id="ln-941" name="ln-941" href="#ln-941"></a><span class="w">    </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">xold</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha</span>
+<a id="ln-942" name="ln-942" href="#ln-942"></a>
+<a id="ln-943" name="ln-943" href="#ln-943"></a><span class="w">    </span><span class="c">!evaluate the function at the new point:</span>
+<a id="ln-944" name="ln-944" href="#ln-944"></a><span class="w">    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fvec</span><span class="p">)</span>
+<a id="ln-945" name="ln-945" href="#ln-945"></a><span class="w">    </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">norm2</span><span class="p">(</span><span class="n">fvec</span><span class="p">)</span>
+<a id="ln-946" name="ln-946" href="#ln-946"></a>
+<a id="ln-947" name="ln-947" href="#ln-947"></a><span class="w">    </span><span class="k">end subroutine </span><span class="n">simple_step</span>
+<a id="ln-948" name="ln-948" href="#ln-948"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-949" name="ln-949" href="#ln-949"></a>
+<a id="ln-950" name="ln-950" href="#ln-950"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-951" name="ln-951" href="#ln-951"></a><span class="c">!&gt;</span>
+<a id="ln-952" name="ln-952" href="#ln-952"></a><span class="c">!  Backtracking line search.</span>
+<a id="ln-953" name="ln-953" href="#ln-953"></a><span class="c">!</span>
+<a id="ln-954" name="ln-954" href="#ln-954"></a><span class="c">!### See also</span>
+<a id="ln-955" name="ln-955" href="#ln-955"></a><span class="c">!  * [Backtracking line search](https://en.wikipedia.org/wiki/Backtracking_line_search)</span>
+<a id="ln-956" name="ln-956" href="#ln-956"></a><span class="c">!</span>
+<a id="ln-957" name="ln-957" href="#ln-957"></a><span class="c">!@note Either `fjac` or `fjac_sparse` should be present.</span>
+<a id="ln-958" name="ln-958" href="#ln-958"></a>
+<a id="ln-959" name="ln-959" href="#ln-959"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">backtracking_linesearch</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">xold</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">fjac</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
 <a id="ln-960" name="ln-960" href="#ln-960"></a>
-<a id="ln-961" name="ln-961" href="#ln-961"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">verbose</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-962" name="ln-962" href="#ln-962"></a><span class="k">        write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(1P,*(A,1X,E16.6))&#39;</span><span class="p">)</span><span class="w"> </span><span class="s1">&#39;        slope    = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">slope</span>
-<a id="ln-963" name="ln-963" href="#ln-963"></a><span class="w">        </span><span class="k">write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(1P,*(A,1X,E16.6))&#39;</span><span class="p">)</span><span class="w"> </span><span class="s1">&#39;        t        = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">t</span>
-<a id="ln-964" name="ln-964" href="#ln-964"></a><span class="w">    </span><span class="k">end if</span>
-<a id="ln-965" name="ln-965" href="#ln-965"></a>
-<a id="ln-966" name="ln-966" href="#ln-966"></a><span class="w">    </span><span class="c">! perform the line search:</span>
-<a id="ln-967" name="ln-967" href="#ln-967"></a><span class="w">    </span><span class="n">min_alpha_reached</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
-<a id="ln-968" name="ln-968" href="#ln-968"></a><span class="w">    </span><span class="n">alpha</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="w">  </span><span class="c">! start with the largest step</span>
-<a id="ln-969" name="ln-969" href="#ln-969"></a><span class="w">    </span><span class="k">do</span>
-<a id="ln-970" name="ln-970" href="#ln-970"></a>
-<a id="ln-971" name="ln-971" href="#ln-971"></a><span class="k">        </span><span class="n">xtmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">xold</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">alpha</span>
-<a id="ln-972" name="ln-972" href="#ln-972"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="p">(</span><span class="n">xtmp</span><span class="p">,</span><span class="n">fvectmp</span><span class="p">)</span>
-<a id="ln-973" name="ln-973" href="#ln-973"></a><span class="w">        </span><span class="n">ftmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">norm2</span><span class="p">(</span><span class="n">fvectmp</span><span class="p">)</span>
-<a id="ln-974" name="ln-974" href="#ln-974"></a>
-<a id="ln-975" name="ln-975" href="#ln-975"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">verbose</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-976" name="ln-976" href="#ln-976"></a><span class="k">            write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(1P,*(A,1X,E16.6))&#39;</span><span class="p">)</span><span class="w">          </span><span class="s1">&#39;        alpha    = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">alpha</span><span class="p">,</span><span class="w">    </span><span class="s1">&#39; f       = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">ftmp</span>
-<a id="ln-977" name="ln-977" href="#ln-977"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">f</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">ftmp</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">alpha</span><span class="o">*</span><span class="n">t</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-978" name="ln-978" href="#ln-978"></a><span class="k">                write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(1P,2(A,1X,E16.6),1X,A)&#39;</span><span class="p">)</span><span class="w"> </span><span class="s1">&#39;        f - ftmp = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">ftmp</span><span class="p">,</span><span class="w"> </span><span class="s1">&#39; alpha*t = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">alpha</span><span class="o">*</span><span class="n">t</span><span class="p">,</span><span class="w"> </span><span class="s1">&#39; [ACCEPTED]&#39;</span>
-<a id="ln-979" name="ln-979" href="#ln-979"></a><span class="w">            </span><span class="k">else</span>
-<a id="ln-980" name="ln-980" href="#ln-980"></a><span class="k">                write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(1P,*(A,1X,E16.6))&#39;</span><span class="p">)</span><span class="w">      </span><span class="s1">&#39;        f - ftmp = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">ftmp</span><span class="p">,</span><span class="w"> </span><span class="s1">&#39; alpha*t = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">alpha</span><span class="o">*</span><span class="n">t</span>
-<a id="ln-981" name="ln-981" href="#ln-981"></a><span class="w">            </span><span class="k">end if</span>
-<a id="ln-982" name="ln-982" href="#ln-982"></a><span class="k">        end if</span>
-<a id="ln-983" name="ln-983" href="#ln-983"></a>
-<a id="ln-984" name="ln-984" href="#ln-984"></a><span class="k">        if</span><span class="w"> </span><span class="p">(((</span><span class="n">f</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">ftmp</span><span class="p">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.0_wp</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">alpha</span><span class="o">*</span><span class="n">t</span><span class="p">)</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">min_alpha_reached</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-985" name="ln-985" href="#ln-985"></a><span class="k">            if</span><span class="w"> </span><span class="p">(</span><span class="n">min_alpha_reached</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-986" name="ln-986" href="#ln-986"></a><span class="k">                write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(A)&#39;</span><span class="p">)</span><span class="w"> </span><span class="s1">&#39;        Minimum alpha reached&#39;</span>
-<a id="ln-987" name="ln-987" href="#ln-987"></a><span class="w">            </span><span class="k">end if</span>
-<a id="ln-988" name="ln-988" href="#ln-988"></a><span class="w">            </span><span class="c">! Armijo-Goldstein condition is satisfied</span>
-<a id="ln-989" name="ln-989" href="#ln-989"></a><span class="w">            </span><span class="c">! (or the min step has been reached)</span>
-<a id="ln-990" name="ln-990" href="#ln-990"></a><span class="w">            </span><span class="n">x</span><span class="w">    </span><span class="o">=</span><span class="w"> </span><span class="n">xtmp</span>
-<a id="ln-991" name="ln-991" href="#ln-991"></a><span class="w">            </span><span class="n">fvec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fvectmp</span>
-<a id="ln-992" name="ln-992" href="#ln-992"></a><span class="w">            </span><span class="n">f</span><span class="w">    </span><span class="o">=</span><span class="w"> </span><span class="n">ftmp</span>
-<a id="ln-993" name="ln-993" href="#ln-993"></a><span class="w">            </span><span class="k">exit</span>
-<a id="ln-994" name="ln-994" href="#ln-994"></a><span class="k">        end if</span>
-<a id="ln-995" name="ln-995" href="#ln-995"></a><span class="k">        </span><span class="n">alpha</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">alpha</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">tau</span><span class="w"> </span><span class="c">! reduce step size</span>
-<a id="ln-996" name="ln-996" href="#ln-996"></a>
-<a id="ln-997" name="ln-997" href="#ln-997"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alpha</span><span class="o">&lt;=</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-998" name="ln-998" href="#ln-998"></a><span class="k">            </span><span class="n">alpha</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span>
-<a id="ln-999" name="ln-999" href="#ln-999"></a><span class="w">            </span><span class="n">min_alpha_reached</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">true</span><span class="p">.</span><span class="w"> </span><span class="c">! will stop on the next step</span>
-<a id="ln-1000" name="ln-1000" href="#ln-1000"></a><span class="w">        </span><span class="k">end if</span>
-<a id="ln-1001" name="ln-1001" href="#ln-1001"></a>
-<a id="ln-1002" name="ln-1002" href="#ln-1002"></a><span class="k">    end do</span>
+<a id="ln-961" name="ln-961" href="#ln-961"></a><span class="w">    </span><span class="k">implicit none</span>
+<a id="ln-962" name="ln-962" href="#ln-962"></a>
+<a id="ln-963" name="ln-963" href="#ln-963"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-964" name="ln-964" href="#ln-964"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xold</span><span class="w">      </span><span class="c">!! previous value of `x`</span>
+<a id="ln-965" name="ln-965" href="#ln-965"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">p</span><span class="w">         </span><span class="c">!! search direction</span>
+<a id="ln-966" name="ln-966" href="#ln-966"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span><span class="w">        </span><span class="c">!! new `x`</span>
+<a id="ln-967" name="ln-967" href="#ln-967"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span><span class="w">                      </span><span class="c">!! magnitude of `fvec`</span>
+<a id="ln-968" name="ln-968" href="#ln-968"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec</span><span class="w">   </span><span class="c">!! function vector</span>
+<a id="ln-969" name="ln-969" href="#ln-969"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac</span><span class="w"> </span><span class="c">!! jacobian matrix [dense]</span>
+<a id="ln-970" name="ln-970" href="#ln-970"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac_sparse</span><span class="w"> </span><span class="c">!! jacobian matrix [sparse]</span>
+<a id="ln-971" name="ln-971" href="#ln-971"></a>
+<a id="ln-972" name="ln-972" href="#ln-972"></a><span class="w">    </span><span class="kt">integer</span><span class="w">    </span><span class="kd">::</span><span class="w"> </span><span class="n">i</span><span class="w">                  </span><span class="c">!! counter</span>
+<a id="ln-973" name="ln-973" href="#ln-973"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">slope</span><span class="w">              </span><span class="c">!! local slope of the function of `alpha` along the search direction used for line search</span>
+<a id="ln-974" name="ln-974" href="#ln-974"></a><span class="w">    </span><span class="kt">logical</span><span class="w">    </span><span class="kd">::</span><span class="w"> </span><span class="n">min_alpha_reached</span><span class="w">  </span><span class="c">!! if the minimum step size is reached during the line search</span>
+<a id="ln-975" name="ln-975" href="#ln-975"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">alpha</span><span class="w">              </span><span class="c">!! `alpha` for the line search</span>
+<a id="ln-976" name="ln-976" href="#ln-976"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">ftmp</span><span class="w">               </span><span class="c">!! `f` value for linesearch</span>
+<a id="ln-977" name="ln-977" href="#ln-977"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w">   </span><span class="kd">::</span><span class="w"> </span><span class="n">t</span><span class="w">                  </span><span class="c">!! used for line search</span>
+<a id="ln-978" name="ln-978" href="#ln-978"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">gradf</span><span class="w">      </span><span class="c">!! line search objective function gradient vector</span>
+<a id="ln-979" name="ln-979" href="#ln-979"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xtmp</span><span class="w">       </span><span class="c">!! `x` value for linesearch</span>
+<a id="ln-980" name="ln-980" href="#ln-980"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvectmp</span><span class="w">    </span><span class="c">!! `fvec` value for linesearch</span>
+<a id="ln-981" name="ln-981" href="#ln-981"></a>
+<a id="ln-982" name="ln-982" href="#ln-982"></a><span class="w">    </span><span class="c">! allocate arrays:</span>
+<a id="ln-983" name="ln-983" href="#ln-983"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">gradf</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">))</span>
+<a id="ln-984" name="ln-984" href="#ln-984"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">xtmp</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">))</span>
+<a id="ln-985" name="ln-985" href="#ln-985"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">fvectmp</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">))</span>
+<a id="ln-986" name="ln-986" href="#ln-986"></a>
+<a id="ln-987" name="ln-987" href="#ln-987"></a><span class="w">    </span><span class="c">! compute the gradient of the function to be minimized</span>
+<a id="ln-988" name="ln-988" href="#ln-988"></a><span class="w">    </span><span class="c">! (which in this case is 1/2 the norm of fvec). Use the chain</span>
+<a id="ln-989" name="ln-989" href="#ln-989"></a><span class="w">    </span><span class="c">! rule and the Jacobian matrix already computed.</span>
+<a id="ln-990" name="ln-990" href="#ln-990"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="nb">present</span><span class="p">(</span><span class="n">fjac</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-991" name="ln-991" href="#ln-991"></a><span class="w">        </span><span class="c">! dense</span>
+<a id="ln-992" name="ln-992" href="#ln-992"></a><span class="w">        </span><span class="k">do </span><span class="n">i</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n</span>
+<a id="ln-993" name="ln-993" href="#ln-993"></a><span class="w">            </span><span class="n">gradf</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">dot_product</span><span class="p">(</span><span class="n">fvec</span><span class="p">,</span><span class="n">fjac</span><span class="p">(:,</span><span class="n">i</span><span class="p">))</span>
+<a id="ln-994" name="ln-994" href="#ln-994"></a><span class="w">        </span><span class="k">end do</span>
+<a id="ln-995" name="ln-995" href="#ln-995"></a><span class="k">    else</span>
+<a id="ln-996" name="ln-996" href="#ln-996"></a><span class="w">        </span><span class="c">! sparse</span>
+<a id="ln-997" name="ln-997" href="#ln-997"></a><span class="w">        </span><span class="k">do </span><span class="n">i</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">n</span>
+<a id="ln-998" name="ln-998" href="#ln-998"></a><span class="w">            </span><span class="n">gradf</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">dot_product</span><span class="p">(</span><span class="n">fvec</span><span class="p">,</span><span class="nb">pack</span><span class="p">(</span><span class="n">fjac_sparse</span><span class="p">,</span><span class="n">mask</span><span class="o">=</span><span class="n">me</span><span class="p">%</span><span class="n">icol</span><span class="o">==</span><span class="n">i</span><span class="p">))</span>
+<a id="ln-999" name="ln-999" href="#ln-999"></a><span class="w">        </span><span class="k">end do</span>
+<a id="ln-1000" name="ln-1000" href="#ln-1000"></a><span class="k">    end if</span>
+<a id="ln-1001" name="ln-1001" href="#ln-1001"></a><span class="k">    </span><span class="n">slope</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">dot_product</span><span class="p">(</span><span class="n">p</span><span class="p">,</span><span class="w"> </span><span class="n">gradf</span><span class="p">)</span>
+<a id="ln-1002" name="ln-1002" href="#ln-1002"></a><span class="w">    </span><span class="n">t</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">-</span><span class="n">me</span><span class="p">%</span><span class="n">c</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">slope</span>
 <a id="ln-1003" name="ln-1003" href="#ln-1003"></a>
-<a id="ln-1004" name="ln-1004" href="#ln-1004"></a><span class="k">    end subroutine </span><span class="n">backtracking_linesearch</span>
-<a id="ln-1005" name="ln-1005" href="#ln-1005"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-1006" name="ln-1006" href="#ln-1006"></a>
-<a id="ln-1007" name="ln-1007" href="#ln-1007"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-1008" name="ln-1008" href="#ln-1008"></a><span class="c">!&gt;</span>
-<a id="ln-1009" name="ln-1009" href="#ln-1009"></a><span class="c">!  An exact linesearch that uses a derivative-free minimizer to</span>
-<a id="ln-1010" name="ln-1010" href="#ln-1010"></a><span class="c">!  find the minimum value of `f(x)` between</span>
-<a id="ln-1011" name="ln-1011" href="#ln-1011"></a><span class="c">!  `x = xold + p * alpha_min` and</span>
-<a id="ln-1012" name="ln-1012" href="#ln-1012"></a><span class="c">!  `x = xold + p * alpha_max`.</span>
-<a id="ln-1013" name="ln-1013" href="#ln-1013"></a><span class="c">!</span>
-<a id="ln-1014" name="ln-1014" href="#ln-1014"></a><span class="c">!  Usually this is overkill and not necessary, but is here as an option for testing.</span>
-<a id="ln-1015" name="ln-1015" href="#ln-1015"></a>
-<a id="ln-1016" name="ln-1016" href="#ln-1016"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">exact_linesearch</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">xold</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">fjac</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
+<a id="ln-1004" name="ln-1004" href="#ln-1004"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">verbose</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-1005" name="ln-1005" href="#ln-1005"></a><span class="k">        write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(1P,*(A,1X,E16.6))&#39;</span><span class="p">)</span><span class="w"> </span><span class="s1">&#39;        slope    = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">slope</span>
+<a id="ln-1006" name="ln-1006" href="#ln-1006"></a><span class="w">        </span><span class="k">write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(1P,*(A,1X,E16.6))&#39;</span><span class="p">)</span><span class="w"> </span><span class="s1">&#39;        t        = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">t</span>
+<a id="ln-1007" name="ln-1007" href="#ln-1007"></a><span class="w">    </span><span class="k">end if</span>
+<a id="ln-1008" name="ln-1008" href="#ln-1008"></a>
+<a id="ln-1009" name="ln-1009" href="#ln-1009"></a><span class="w">    </span><span class="c">! perform the line search:</span>
+<a id="ln-1010" name="ln-1010" href="#ln-1010"></a><span class="w">    </span><span class="n">min_alpha_reached</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">false</span><span class="p">.</span>
+<a id="ln-1011" name="ln-1011" href="#ln-1011"></a><span class="w">    </span><span class="n">alpha</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="w">  </span><span class="c">! start with the largest step</span>
+<a id="ln-1012" name="ln-1012" href="#ln-1012"></a><span class="w">    </span><span class="k">do</span>
+<a id="ln-1013" name="ln-1013" href="#ln-1013"></a>
+<a id="ln-1014" name="ln-1014" href="#ln-1014"></a><span class="k">        </span><span class="n">xtmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">xold</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">alpha</span>
+<a id="ln-1015" name="ln-1015" href="#ln-1015"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="p">(</span><span class="n">xtmp</span><span class="p">,</span><span class="n">fvectmp</span><span class="p">)</span>
+<a id="ln-1016" name="ln-1016" href="#ln-1016"></a><span class="w">        </span><span class="n">ftmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">norm2</span><span class="p">(</span><span class="n">fvectmp</span><span class="p">)</span>
 <a id="ln-1017" name="ln-1017" href="#ln-1017"></a>
-<a id="ln-1018" name="ln-1018" href="#ln-1018"></a><span class="w">    </span><span class="k">implicit none</span>
-<a id="ln-1019" name="ln-1019" href="#ln-1019"></a>
-<a id="ln-1020" name="ln-1020" href="#ln-1020"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
-<a id="ln-1021" name="ln-1021" href="#ln-1021"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xold</span><span class="w">      </span><span class="c">!! previous value of `x`</span>
-<a id="ln-1022" name="ln-1022" href="#ln-1022"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">p</span><span class="w">         </span><span class="c">!! search direction</span>
-<a id="ln-1023" name="ln-1023" href="#ln-1023"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span><span class="w">        </span><span class="c">!! new `x`</span>
-<a id="ln-1024" name="ln-1024" href="#ln-1024"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span><span class="w">                      </span><span class="c">!! magnitude of `fvec`</span>
-<a id="ln-1025" name="ln-1025" href="#ln-1025"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec</span><span class="w">   </span><span class="c">!! function vector</span>
-<a id="ln-1026" name="ln-1026" href="#ln-1026"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac</span><span class="w"> </span><span class="c">!! jacobian matrix [dense]</span>
-<a id="ln-1027" name="ln-1027" href="#ln-1027"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac_sparse</span><span class="w"> </span><span class="c">!! jacobian matrix [sparse]</span>
-<a id="ln-1028" name="ln-1028" href="#ln-1028"></a>
-<a id="ln-1029" name="ln-1029" href="#ln-1029"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xnew</span><span class="w"> </span><span class="c">!! used in [[func_for_fmin]]</span>
-<a id="ln-1030" name="ln-1030" href="#ln-1030"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">alpha_min</span>
-<a id="ln-1031" name="ln-1031" href="#ln-1031"></a>
-<a id="ln-1032" name="ln-1032" href="#ln-1032"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">xnew</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">))</span>
-<a id="ln-1033" name="ln-1033" href="#ln-1033"></a>
-<a id="ln-1034" name="ln-1034" href="#ln-1034"></a><span class="w">    </span><span class="c">! find the minimum value of f in the range of alphas:</span>
-<a id="ln-1035" name="ln-1035" href="#ln-1035"></a><span class="w">    </span><span class="n">alpha_min</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fmin</span><span class="p">(</span><span class="n">func_for_fmin</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">fmin_tol</span><span class="p">)</span>
-<a id="ln-1036" name="ln-1036" href="#ln-1036"></a>
-<a id="ln-1037" name="ln-1037" href="#ln-1037"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">verbose</span><span class="p">)</span><span class="w"> </span><span class="k">write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(1P,*(A,1X,E16.6))&#39;</span><span class="p">)</span><span class="w"> </span><span class="s1">&#39;        alpha_min = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">alpha_min</span>
-<a id="ln-1038" name="ln-1038" href="#ln-1038"></a>
-<a id="ln-1039" name="ln-1039" href="#ln-1039"></a><span class="w">    </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">xold</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">alpha_min</span>
-<a id="ln-1040" name="ln-1040" href="#ln-1040"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">all</span><span class="p">(</span><span class="n">x</span><span class="o">==</span><span class="n">xnew</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
-<a id="ln-1041" name="ln-1041" href="#ln-1041"></a><span class="w">        </span><span class="c">! already computed in the func</span>
-<a id="ln-1042" name="ln-1042" href="#ln-1042"></a><span class="w">    </span><span class="k">else</span>
-<a id="ln-1043" name="ln-1043" href="#ln-1043"></a><span class="k">        call </span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fvec</span><span class="p">)</span>
-<a id="ln-1044" name="ln-1044" href="#ln-1044"></a><span class="w">        </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">norm2</span><span class="p">(</span><span class="n">fvec</span><span class="p">)</span>
-<a id="ln-1045" name="ln-1045" href="#ln-1045"></a><span class="w">    </span><span class="k">end if</span>
+<a id="ln-1018" name="ln-1018" href="#ln-1018"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">verbose</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-1019" name="ln-1019" href="#ln-1019"></a><span class="k">            write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(1P,*(A,1X,E16.6))&#39;</span><span class="p">)</span><span class="w">          </span><span class="s1">&#39;        alpha    = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">alpha</span><span class="p">,</span><span class="w">    </span><span class="s1">&#39; f       = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">ftmp</span>
+<a id="ln-1020" name="ln-1020" href="#ln-1020"></a><span class="w">            </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">f</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">ftmp</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">alpha</span><span class="o">*</span><span class="n">t</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-1021" name="ln-1021" href="#ln-1021"></a><span class="k">                write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(1P,2(A,1X,E16.6),1X,A)&#39;</span><span class="p">)</span><span class="w"> </span><span class="s1">&#39;        f - ftmp = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">ftmp</span><span class="p">,</span><span class="w"> </span><span class="s1">&#39; alpha*t = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">alpha</span><span class="o">*</span><span class="n">t</span><span class="p">,</span><span class="w"> </span><span class="s1">&#39; [ACCEPTED]&#39;</span>
+<a id="ln-1022" name="ln-1022" href="#ln-1022"></a><span class="w">            </span><span class="k">else</span>
+<a id="ln-1023" name="ln-1023" href="#ln-1023"></a><span class="k">                write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(1P,*(A,1X,E16.6))&#39;</span><span class="p">)</span><span class="w">      </span><span class="s1">&#39;        f - ftmp = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">f</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">ftmp</span><span class="p">,</span><span class="w"> </span><span class="s1">&#39; alpha*t = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">alpha</span><span class="o">*</span><span class="n">t</span>
+<a id="ln-1024" name="ln-1024" href="#ln-1024"></a><span class="w">            </span><span class="k">end if</span>
+<a id="ln-1025" name="ln-1025" href="#ln-1025"></a><span class="k">        end if</span>
+<a id="ln-1026" name="ln-1026" href="#ln-1026"></a>
+<a id="ln-1027" name="ln-1027" href="#ln-1027"></a><span class="k">        if</span><span class="w"> </span><span class="p">(((</span><span class="n">f</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">ftmp</span><span class="p">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="mf">2.0_wp</span><span class="w"> </span><span class="o">&gt;=</span><span class="w"> </span><span class="n">alpha</span><span class="o">*</span><span class="n">t</span><span class="p">)</span><span class="w"> </span><span class="p">.</span><span class="nb">or</span><span class="p">.</span><span class="w"> </span><span class="n">min_alpha_reached</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-1028" name="ln-1028" href="#ln-1028"></a><span class="k">            if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">verbose</span><span class="w"> </span><span class="p">.</span><span class="nb">and</span><span class="p">.</span><span class="w"> </span><span class="n">min_alpha_reached</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-1029" name="ln-1029" href="#ln-1029"></a><span class="k">                write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(A)&#39;</span><span class="p">)</span><span class="w"> </span><span class="s1">&#39;        Minimum alpha reached&#39;</span>
+<a id="ln-1030" name="ln-1030" href="#ln-1030"></a><span class="w">            </span><span class="k">end if</span>
+<a id="ln-1031" name="ln-1031" href="#ln-1031"></a><span class="w">            </span><span class="c">! Armijo-Goldstein condition is satisfied</span>
+<a id="ln-1032" name="ln-1032" href="#ln-1032"></a><span class="w">            </span><span class="c">! (or the min step has been reached)</span>
+<a id="ln-1033" name="ln-1033" href="#ln-1033"></a><span class="w">            </span><span class="n">x</span><span class="w">    </span><span class="o">=</span><span class="w"> </span><span class="n">xtmp</span>
+<a id="ln-1034" name="ln-1034" href="#ln-1034"></a><span class="w">            </span><span class="n">fvec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fvectmp</span>
+<a id="ln-1035" name="ln-1035" href="#ln-1035"></a><span class="w">            </span><span class="n">f</span><span class="w">    </span><span class="o">=</span><span class="w"> </span><span class="n">ftmp</span>
+<a id="ln-1036" name="ln-1036" href="#ln-1036"></a><span class="w">            </span><span class="k">exit</span>
+<a id="ln-1037" name="ln-1037" href="#ln-1037"></a><span class="k">        end if</span>
+<a id="ln-1038" name="ln-1038" href="#ln-1038"></a><span class="k">        </span><span class="n">alpha</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">alpha</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">tau</span><span class="w"> </span><span class="c">! reduce step size</span>
+<a id="ln-1039" name="ln-1039" href="#ln-1039"></a>
+<a id="ln-1040" name="ln-1040" href="#ln-1040"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">alpha</span><span class="o">&lt;=</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="p">)</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-1041" name="ln-1041" href="#ln-1041"></a><span class="k">            </span><span class="n">alpha</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span>
+<a id="ln-1042" name="ln-1042" href="#ln-1042"></a><span class="w">            </span><span class="n">min_alpha_reached</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">.</span><span class="n">true</span><span class="p">.</span><span class="w"> </span><span class="c">! will stop on the next step</span>
+<a id="ln-1043" name="ln-1043" href="#ln-1043"></a><span class="w">        </span><span class="k">end if</span>
+<a id="ln-1044" name="ln-1044" href="#ln-1044"></a>
+<a id="ln-1045" name="ln-1045" href="#ln-1045"></a><span class="k">    end do</span>
 <a id="ln-1046" name="ln-1046" href="#ln-1046"></a>
-<a id="ln-1047" name="ln-1047" href="#ln-1047"></a><span class="k">contains</span>
-<a id="ln-1048" name="ln-1048" href="#ln-1048"></a>
-<a id="ln-1049" name="ln-1049" href="#ln-1049"></a><span class="k">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="k">function </span><span class="n">func_for_fmin</span><span class="p">(</span><span class="n">alpha</span><span class="p">)</span>
-<a id="ln-1050" name="ln-1050" href="#ln-1050"></a><span class="w">    </span><span class="c">!! function for [[fmin]]</span>
-<a id="ln-1051" name="ln-1051" href="#ln-1051"></a><span class="w">    </span><span class="k">implicit none</span>
-<a id="ln-1052" name="ln-1052" href="#ln-1052"></a><span class="k">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">alpha</span><span class="w"> </span><span class="c">!! indep variable</span>
-<a id="ln-1053" name="ln-1053" href="#ln-1053"></a>
-<a id="ln-1054" name="ln-1054" href="#ln-1054"></a><span class="w">    </span><span class="n">xnew</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">xold</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">alpha</span>
-<a id="ln-1055" name="ln-1055" href="#ln-1055"></a><span class="w">    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="p">(</span><span class="n">xnew</span><span class="p">,</span><span class="n">fvec</span><span class="p">)</span>
-<a id="ln-1056" name="ln-1056" href="#ln-1056"></a><span class="w">    </span><span class="n">func_for_fmin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">norm2</span><span class="p">(</span><span class="n">fvec</span><span class="p">)</span><span class="w"> </span><span class="c">! return result</span>
-<a id="ln-1057" name="ln-1057" href="#ln-1057"></a>
-<a id="ln-1058" name="ln-1058" href="#ln-1058"></a><span class="w">    </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">func_for_fmin</span><span class="w"> </span><span class="c">! just in case this is the solution</span>
-<a id="ln-1059" name="ln-1059" href="#ln-1059"></a>
-<a id="ln-1060" name="ln-1060" href="#ln-1060"></a><span class="w">    </span><span class="k">end function </span><span class="n">func_for_fmin</span>
-<a id="ln-1061" name="ln-1061" href="#ln-1061"></a>
-<a id="ln-1062" name="ln-1062" href="#ln-1062"></a><span class="w">    </span><span class="k">end subroutine </span><span class="n">exact_linesearch</span>
-<a id="ln-1063" name="ln-1063" href="#ln-1063"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-1064" name="ln-1064" href="#ln-1064"></a>
-<a id="ln-1065" name="ln-1065" href="#ln-1065"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-1066" name="ln-1066" href="#ln-1066"></a><span class="c">!&gt;</span>
-<a id="ln-1067" name="ln-1067" href="#ln-1067"></a><span class="c">!  A simple search that just evaluates the function at a specified</span>
-<a id="ln-1068" name="ln-1068" href="#ln-1068"></a><span class="c">!  number of points and picks the one with the minimum function value.</span>
-<a id="ln-1069" name="ln-1069" href="#ln-1069"></a>
-<a id="ln-1070" name="ln-1070" href="#ln-1070"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">fixed_point_linesearch</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">xold</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">fjac</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
+<a id="ln-1047" name="ln-1047" href="#ln-1047"></a><span class="k">    end subroutine </span><span class="n">backtracking_linesearch</span>
+<a id="ln-1048" name="ln-1048" href="#ln-1048"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-1049" name="ln-1049" href="#ln-1049"></a>
+<a id="ln-1050" name="ln-1050" href="#ln-1050"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-1051" name="ln-1051" href="#ln-1051"></a><span class="c">!&gt;</span>
+<a id="ln-1052" name="ln-1052" href="#ln-1052"></a><span class="c">!  An exact linesearch that uses a derivative-free minimizer to</span>
+<a id="ln-1053" name="ln-1053" href="#ln-1053"></a><span class="c">!  find the minimum value of `f(x)` between</span>
+<a id="ln-1054" name="ln-1054" href="#ln-1054"></a><span class="c">!  `x = xold + p * alpha_min` and</span>
+<a id="ln-1055" name="ln-1055" href="#ln-1055"></a><span class="c">!  `x = xold + p * alpha_max`.</span>
+<a id="ln-1056" name="ln-1056" href="#ln-1056"></a><span class="c">!</span>
+<a id="ln-1057" name="ln-1057" href="#ln-1057"></a><span class="c">!  Usually this is overkill and not necessary, but is here as an option for testing.</span>
+<a id="ln-1058" name="ln-1058" href="#ln-1058"></a>
+<a id="ln-1059" name="ln-1059" href="#ln-1059"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">exact_linesearch</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">xold</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">fjac</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
+<a id="ln-1060" name="ln-1060" href="#ln-1060"></a>
+<a id="ln-1061" name="ln-1061" href="#ln-1061"></a><span class="w">    </span><span class="k">implicit none</span>
+<a id="ln-1062" name="ln-1062" href="#ln-1062"></a>
+<a id="ln-1063" name="ln-1063" href="#ln-1063"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-1064" name="ln-1064" href="#ln-1064"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xold</span><span class="w">      </span><span class="c">!! previous value of `x`</span>
+<a id="ln-1065" name="ln-1065" href="#ln-1065"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">p</span><span class="w">         </span><span class="c">!! search direction</span>
+<a id="ln-1066" name="ln-1066" href="#ln-1066"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span><span class="w">        </span><span class="c">!! new `x`</span>
+<a id="ln-1067" name="ln-1067" href="#ln-1067"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span><span class="w">                      </span><span class="c">!! magnitude of `fvec`</span>
+<a id="ln-1068" name="ln-1068" href="#ln-1068"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec</span><span class="w">   </span><span class="c">!! function vector</span>
+<a id="ln-1069" name="ln-1069" href="#ln-1069"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac</span><span class="w"> </span><span class="c">!! jacobian matrix [dense]</span>
+<a id="ln-1070" name="ln-1070" href="#ln-1070"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac_sparse</span><span class="w"> </span><span class="c">!! jacobian matrix [sparse]</span>
 <a id="ln-1071" name="ln-1071" href="#ln-1071"></a>
-<a id="ln-1072" name="ln-1072" href="#ln-1072"></a><span class="w">    </span><span class="k">implicit none</span>
-<a id="ln-1073" name="ln-1073" href="#ln-1073"></a>
-<a id="ln-1074" name="ln-1074" href="#ln-1074"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
-<a id="ln-1075" name="ln-1075" href="#ln-1075"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xold</span><span class="w">      </span><span class="c">!! previous value of `x`</span>
-<a id="ln-1076" name="ln-1076" href="#ln-1076"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">p</span><span class="w">         </span><span class="c">!! search direction</span>
-<a id="ln-1077" name="ln-1077" href="#ln-1077"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span><span class="w">        </span><span class="c">!! new `x`</span>
-<a id="ln-1078" name="ln-1078" href="#ln-1078"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span><span class="w">                      </span><span class="c">!! magnitude of `fvec`</span>
-<a id="ln-1079" name="ln-1079" href="#ln-1079"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec</span><span class="w">   </span><span class="c">!! function vector</span>
-<a id="ln-1080" name="ln-1080" href="#ln-1080"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac</span><span class="w"> </span><span class="c">!! jacobian matrix [dense]</span>
-<a id="ln-1081" name="ln-1081" href="#ln-1081"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac_sparse</span><span class="w"> </span><span class="c">!! jacobian matrix [sparse]</span>
-<a id="ln-1082" name="ln-1082" href="#ln-1082"></a>
-<a id="ln-1083" name="ln-1083" href="#ln-1083"></a><span class="w">    </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="c">!! counter</span>
-<a id="ln-1084" name="ln-1084" href="#ln-1084"></a><span class="w">    </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">n_points</span><span class="w"> </span><span class="c">!! number of points to compute</span>
-<a id="ln-1085" name="ln-1085" href="#ln-1085"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">alphas_to_try</span><span class="w"> </span><span class="c">!! set of `alpha` values to try</span>
-<a id="ln-1086" name="ln-1086" href="#ln-1086"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">x_tmp</span><span class="w"> </span><span class="c">!! temp `x`</span>
-<a id="ln-1087" name="ln-1087" href="#ln-1087"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec_tmp</span><span class="w"> </span><span class="c">!! temp `fvec`</span>
-<a id="ln-1088" name="ln-1088" href="#ln-1088"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">f_tmp</span><span class="w"> </span><span class="c">!! temp `f`</span>
-<a id="ln-1089" name="ln-1089" href="#ln-1089"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">step_size</span><span class="w"> </span><span class="c">!! step size for `alpha`</span>
-<a id="ln-1090" name="ln-1090" href="#ln-1090"></a><span class="w">    </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="c">!! number of steps to divide the interval</span>
+<a id="ln-1072" name="ln-1072" href="#ln-1072"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xnew</span><span class="w"> </span><span class="c">!! used in [[func_for_fmin]]</span>
+<a id="ln-1073" name="ln-1073" href="#ln-1073"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">alpha_min</span>
+<a id="ln-1074" name="ln-1074" href="#ln-1074"></a>
+<a id="ln-1075" name="ln-1075" href="#ln-1075"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">xnew</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">))</span>
+<a id="ln-1076" name="ln-1076" href="#ln-1076"></a>
+<a id="ln-1077" name="ln-1077" href="#ln-1077"></a><span class="w">    </span><span class="c">! find the minimum value of f in the range of alphas:</span>
+<a id="ln-1078" name="ln-1078" href="#ln-1078"></a><span class="w">    </span><span class="n">alpha_min</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fmin</span><span class="p">(</span><span class="n">func_for_fmin</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="p">,</span><span class="n">me</span><span class="p">%</span><span class="n">fmin_tol</span><span class="p">)</span>
+<a id="ln-1079" name="ln-1079" href="#ln-1079"></a>
+<a id="ln-1080" name="ln-1080" href="#ln-1080"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">verbose</span><span class="p">)</span><span class="w"> </span><span class="k">write</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">iunit</span><span class="p">,</span><span class="s1">&#39;(1P,*(A,1X,E16.6))&#39;</span><span class="p">)</span><span class="w"> </span><span class="s1">&#39;        alpha_min = &#39;</span><span class="p">,</span><span class="w"> </span><span class="n">alpha_min</span>
+<a id="ln-1081" name="ln-1081" href="#ln-1081"></a>
+<a id="ln-1082" name="ln-1082" href="#ln-1082"></a><span class="w">    </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">xold</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">alpha_min</span>
+<a id="ln-1083" name="ln-1083" href="#ln-1083"></a><span class="w">    </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="k">all</span><span class="p">(</span><span class="n">x</span><span class="o">==</span><span class="n">xnew</span><span class="p">))</span><span class="w"> </span><span class="k">then</span>
+<a id="ln-1084" name="ln-1084" href="#ln-1084"></a><span class="w">        </span><span class="c">! already computed in the func</span>
+<a id="ln-1085" name="ln-1085" href="#ln-1085"></a><span class="w">    </span><span class="k">else</span>
+<a id="ln-1086" name="ln-1086" href="#ln-1086"></a><span class="k">        call </span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="p">(</span><span class="n">x</span><span class="p">,</span><span class="n">fvec</span><span class="p">)</span>
+<a id="ln-1087" name="ln-1087" href="#ln-1087"></a><span class="w">        </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">norm2</span><span class="p">(</span><span class="n">fvec</span><span class="p">)</span>
+<a id="ln-1088" name="ln-1088" href="#ln-1088"></a><span class="w">    </span><span class="k">end if</span>
+<a id="ln-1089" name="ln-1089" href="#ln-1089"></a>
+<a id="ln-1090" name="ln-1090" href="#ln-1090"></a><span class="k">contains</span>
 <a id="ln-1091" name="ln-1091" href="#ln-1091"></a>
-<a id="ln-1092" name="ln-1092" href="#ln-1092"></a><span class="w">    </span><span class="c">! 1 o-----------o</span>
-<a id="ln-1093" name="ln-1093" href="#ln-1093"></a><span class="w">    </span><span class="c">! 2 o-----o-----o</span>
-<a id="ln-1094" name="ln-1094" href="#ln-1094"></a><span class="w">    </span><span class="c">! 3 o---o---o---o</span>
-<a id="ln-1095" name="ln-1095" href="#ln-1095"></a>
-<a id="ln-1096" name="ln-1096" href="#ln-1096"></a><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">n_intervals</span>
-<a id="ln-1097" name="ln-1097" href="#ln-1097"></a><span class="w">    </span><span class="n">n_points</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span>
-<a id="ln-1098" name="ln-1098" href="#ln-1098"></a>
-<a id="ln-1099" name="ln-1099" href="#ln-1099"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">alphas_to_try</span><span class="p">(</span><span class="n">n_points</span><span class="p">))</span>
-<a id="ln-1100" name="ln-1100" href="#ln-1100"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">x_tmp</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">))</span>
-<a id="ln-1101" name="ln-1101" href="#ln-1101"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">fvec_tmp</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">))</span>
+<a id="ln-1092" name="ln-1092" href="#ln-1092"></a><span class="k">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="k">function </span><span class="n">func_for_fmin</span><span class="p">(</span><span class="n">alpha</span><span class="p">)</span>
+<a id="ln-1093" name="ln-1093" href="#ln-1093"></a><span class="w">    </span><span class="c">!! function for [[fmin]]</span>
+<a id="ln-1094" name="ln-1094" href="#ln-1094"></a><span class="w">    </span><span class="k">implicit none</span>
+<a id="ln-1095" name="ln-1095" href="#ln-1095"></a><span class="k">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">alpha</span><span class="w"> </span><span class="c">!! indep variable</span>
+<a id="ln-1096" name="ln-1096" href="#ln-1096"></a>
+<a id="ln-1097" name="ln-1097" href="#ln-1097"></a><span class="w">    </span><span class="n">xnew</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">xold</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">alpha</span>
+<a id="ln-1098" name="ln-1098" href="#ln-1098"></a><span class="w">    </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="p">(</span><span class="n">xnew</span><span class="p">,</span><span class="n">fvec</span><span class="p">)</span>
+<a id="ln-1099" name="ln-1099" href="#ln-1099"></a><span class="w">    </span><span class="n">func_for_fmin</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">norm2</span><span class="p">(</span><span class="n">fvec</span><span class="p">)</span><span class="w"> </span><span class="c">! return result</span>
+<a id="ln-1100" name="ln-1100" href="#ln-1100"></a>
+<a id="ln-1101" name="ln-1101" href="#ln-1101"></a><span class="w">    </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">func_for_fmin</span><span class="w"> </span><span class="c">! just in case this is the solution</span>
 <a id="ln-1102" name="ln-1102" href="#ln-1102"></a>
-<a id="ln-1103" name="ln-1103" href="#ln-1103"></a><span class="w">    </span><span class="n">step_size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="p">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="kt">real</span><span class="p">(</span><span class="n">n</span><span class="p">,</span><span class="n">wp</span><span class="p">)</span>
+<a id="ln-1103" name="ln-1103" href="#ln-1103"></a><span class="w">    </span><span class="k">end function </span><span class="n">func_for_fmin</span>
 <a id="ln-1104" name="ln-1104" href="#ln-1104"></a>
-<a id="ln-1105" name="ln-1105" href="#ln-1105"></a><span class="w">    </span><span class="c">! compute the alphas:</span>
-<a id="ln-1106" name="ln-1106" href="#ln-1106"></a><span class="w">    </span><span class="n">alphas_to_try</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span>
-<a id="ln-1107" name="ln-1107" href="#ln-1107"></a><span class="w">    </span><span class="k">do </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">n</span>
-<a id="ln-1108" name="ln-1108" href="#ln-1108"></a><span class="w">        </span><span class="n">alphas_to_try</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">alphas_to_try</span><span class="p">(</span><span class="n">i</span><span class="o">-</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">step_size</span>
-<a id="ln-1109" name="ln-1109" href="#ln-1109"></a><span class="w">    </span><span class="k">end do</span>
-<a id="ln-1110" name="ln-1110" href="#ln-1110"></a><span class="k">    </span><span class="n">alphas_to_try</span><span class="p">(</span><span class="n">n_points</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span>
-<a id="ln-1111" name="ln-1111" href="#ln-1111"></a>
-<a id="ln-1112" name="ln-1112" href="#ln-1112"></a><span class="w">    </span><span class="c">! now compute the functions at these alphas:</span>
-<a id="ln-1113" name="ln-1113" href="#ln-1113"></a><span class="w">    </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">big</span>
-<a id="ln-1114" name="ln-1114" href="#ln-1114"></a><span class="w">    </span><span class="k">do </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">n_points</span>
-<a id="ln-1115" name="ln-1115" href="#ln-1115"></a>
-<a id="ln-1116" name="ln-1116" href="#ln-1116"></a><span class="w">        </span><span class="n">x_tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">xold</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">alphas_to_try</span><span class="p">(</span><span class="n">i</span><span class="p">)</span>
-<a id="ln-1117" name="ln-1117" href="#ln-1117"></a>
-<a id="ln-1118" name="ln-1118" href="#ln-1118"></a><span class="w">        </span><span class="c">! evaluate the function at tthis point:</span>
-<a id="ln-1119" name="ln-1119" href="#ln-1119"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="p">(</span><span class="n">x_tmp</span><span class="p">,</span><span class="n">fvec_tmp</span><span class="p">)</span>
-<a id="ln-1120" name="ln-1120" href="#ln-1120"></a><span class="w">        </span><span class="n">f_tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">norm2</span><span class="p">(</span><span class="n">fvec_tmp</span><span class="p">)</span>
-<a id="ln-1121" name="ln-1121" href="#ln-1121"></a>
-<a id="ln-1122" name="ln-1122" href="#ln-1122"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">f_tmp</span><span class="o">&lt;=</span><span class="n">f</span><span class="p">)</span><span class="w"> </span><span class="k">then</span><span class="w"> </span><span class="c">! new best point</span>
-<a id="ln-1123" name="ln-1123" href="#ln-1123"></a><span class="w">            </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">x_tmp</span>
-<a id="ln-1124" name="ln-1124" href="#ln-1124"></a><span class="w">            </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">f_tmp</span>
-<a id="ln-1125" name="ln-1125" href="#ln-1125"></a><span class="w">            </span><span class="n">fvec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fvec_tmp</span>
-<a id="ln-1126" name="ln-1126" href="#ln-1126"></a><span class="w">        </span><span class="k">end if</span>
-<a id="ln-1127" name="ln-1127" href="#ln-1127"></a>
-<a id="ln-1128" name="ln-1128" href="#ln-1128"></a><span class="k">    end do</span>
-<a id="ln-1129" name="ln-1129" href="#ln-1129"></a>
-<a id="ln-1130" name="ln-1130" href="#ln-1130"></a><span class="k">    end subroutine </span><span class="n">fixed_point_linesearch</span>
-<a id="ln-1131" name="ln-1131" href="#ln-1131"></a><span class="c">!*****************************************************************************************</span>
-<a id="ln-1132" name="ln-1132" href="#ln-1132"></a>
-<a id="ln-1133" name="ln-1133" href="#ln-1133"></a><span class="c">!******************************************************************************************************</span>
-<a id="ln-1134" name="ln-1134" href="#ln-1134"></a><span class="w">    </span><span class="k">end module </span><span class="n">nlesolver_module</span>
-<a id="ln-1135" name="ln-1135" href="#ln-1135"></a><span class="c">!******************************************************************************************************</span>
+<a id="ln-1105" name="ln-1105" href="#ln-1105"></a><span class="w">    </span><span class="k">end subroutine </span><span class="n">exact_linesearch</span>
+<a id="ln-1106" name="ln-1106" href="#ln-1106"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-1107" name="ln-1107" href="#ln-1107"></a>
+<a id="ln-1108" name="ln-1108" href="#ln-1108"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-1109" name="ln-1109" href="#ln-1109"></a><span class="c">!&gt;</span>
+<a id="ln-1110" name="ln-1110" href="#ln-1110"></a><span class="c">!  A simple search that just evaluates the function at a specified</span>
+<a id="ln-1111" name="ln-1111" href="#ln-1111"></a><span class="c">!  number of points and picks the one with the minimum function value.</span>
+<a id="ln-1112" name="ln-1112" href="#ln-1112"></a>
+<a id="ln-1113" name="ln-1113" href="#ln-1113"></a><span class="w">    </span><span class="k">subroutine </span><span class="n">fixed_point_linesearch</span><span class="p">(</span><span class="n">me</span><span class="p">,</span><span class="n">xold</span><span class="p">,</span><span class="n">p</span><span class="p">,</span><span class="n">x</span><span class="p">,</span><span class="n">f</span><span class="p">,</span><span class="n">fvec</span><span class="p">,</span><span class="n">fjac</span><span class="p">,</span><span class="n">fjac_sparse</span><span class="p">)</span>
+<a id="ln-1114" name="ln-1114" href="#ln-1114"></a>
+<a id="ln-1115" name="ln-1115" href="#ln-1115"></a><span class="w">    </span><span class="k">implicit none</span>
+<a id="ln-1116" name="ln-1116" href="#ln-1116"></a>
+<a id="ln-1117" name="ln-1117" href="#ln-1117"></a><span class="k">    class</span><span class="p">(</span><span class="n">nlesolver_type</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">me</span>
+<a id="ln-1118" name="ln-1118" href="#ln-1118"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">xold</span><span class="w">      </span><span class="c">!! previous value of `x`</span>
+<a id="ln-1119" name="ln-1119" href="#ln-1119"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">p</span><span class="w">         </span><span class="c">!! search direction</span>
+<a id="ln-1120" name="ln-1120" href="#ln-1120"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">out</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">x</span><span class="w">        </span><span class="c">!! new `x`</span>
+<a id="ln-1121" name="ln-1121" href="#ln-1121"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">f</span><span class="w">                      </span><span class="c">!! magnitude of `fvec`</span>
+<a id="ln-1122" name="ln-1122" href="#ln-1122"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">),</span><span class="k">intent</span><span class="p">(</span><span class="n">inout</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec</span><span class="w">   </span><span class="c">!! function vector</span>
+<a id="ln-1123" name="ln-1123" href="#ln-1123"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:,:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac</span><span class="w"> </span><span class="c">!! jacobian matrix [dense]</span>
+<a id="ln-1124" name="ln-1124" href="#ln-1124"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">intent</span><span class="p">(</span><span class="n">in</span><span class="p">),</span><span class="k">optional</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fjac_sparse</span><span class="w"> </span><span class="c">!! jacobian matrix [sparse]</span>
+<a id="ln-1125" name="ln-1125" href="#ln-1125"></a>
+<a id="ln-1126" name="ln-1126" href="#ln-1126"></a><span class="w">    </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="c">!! counter</span>
+<a id="ln-1127" name="ln-1127" href="#ln-1127"></a><span class="w">    </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">n_points</span><span class="w"> </span><span class="c">!! number of points to compute</span>
+<a id="ln-1128" name="ln-1128" href="#ln-1128"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">alphas_to_try</span><span class="w"> </span><span class="c">!! set of `alpha` values to try</span>
+<a id="ln-1129" name="ln-1129" href="#ln-1129"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">x_tmp</span><span class="w"> </span><span class="c">!! temp `x`</span>
+<a id="ln-1130" name="ln-1130" href="#ln-1130"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">),</span><span class="k">dimension</span><span class="p">(:),</span><span class="k">allocatable</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">fvec_tmp</span><span class="w"> </span><span class="c">!! temp `fvec`</span>
+<a id="ln-1131" name="ln-1131" href="#ln-1131"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">f_tmp</span><span class="w"> </span><span class="c">!! temp `f`</span>
+<a id="ln-1132" name="ln-1132" href="#ln-1132"></a><span class="w">    </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">step_size</span><span class="w"> </span><span class="c">!! step size for `alpha`</span>
+<a id="ln-1133" name="ln-1133" href="#ln-1133"></a><span class="w">    </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="c">!! number of steps to divide the interval</span>
+<a id="ln-1134" name="ln-1134" href="#ln-1134"></a>
+<a id="ln-1135" name="ln-1135" href="#ln-1135"></a><span class="w">    </span><span class="c">! 1 o-----------o</span>
+<a id="ln-1136" name="ln-1136" href="#ln-1136"></a><span class="w">    </span><span class="c">! 2 o-----o-----o</span>
+<a id="ln-1137" name="ln-1137" href="#ln-1137"></a><span class="w">    </span><span class="c">! 3 o---o---o---o</span>
+<a id="ln-1138" name="ln-1138" href="#ln-1138"></a>
+<a id="ln-1139" name="ln-1139" href="#ln-1139"></a><span class="w">    </span><span class="n">n</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">n_intervals</span>
+<a id="ln-1140" name="ln-1140" href="#ln-1140"></a><span class="w">    </span><span class="n">n_points</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">n</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span>
+<a id="ln-1141" name="ln-1141" href="#ln-1141"></a>
+<a id="ln-1142" name="ln-1142" href="#ln-1142"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">alphas_to_try</span><span class="p">(</span><span class="n">n_points</span><span class="p">))</span>
+<a id="ln-1143" name="ln-1143" href="#ln-1143"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">x_tmp</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">n</span><span class="p">))</span>
+<a id="ln-1144" name="ln-1144" href="#ln-1144"></a><span class="w">    </span><span class="k">allocate</span><span class="p">(</span><span class="n">fvec_tmp</span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">m</span><span class="p">))</span>
+<a id="ln-1145" name="ln-1145" href="#ln-1145"></a>
+<a id="ln-1146" name="ln-1146" href="#ln-1146"></a><span class="w">    </span><span class="n">step_size</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span><span class="p">)</span><span class="w"> </span><span class="o">/</span><span class="w"> </span><span class="kt">real</span><span class="p">(</span><span class="n">n</span><span class="p">,</span><span class="n">wp</span><span class="p">)</span>
+<a id="ln-1147" name="ln-1147" href="#ln-1147"></a>
+<a id="ln-1148" name="ln-1148" href="#ln-1148"></a><span class="w">    </span><span class="c">! compute the alphas:</span>
+<a id="ln-1149" name="ln-1149" href="#ln-1149"></a><span class="w">    </span><span class="n">alphas_to_try</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_min</span>
+<a id="ln-1150" name="ln-1150" href="#ln-1150"></a><span class="w">    </span><span class="k">do </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="n">n</span>
+<a id="ln-1151" name="ln-1151" href="#ln-1151"></a><span class="w">        </span><span class="n">alphas_to_try</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">alphas_to_try</span><span class="p">(</span><span class="n">i</span><span class="o">-</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">step_size</span>
+<a id="ln-1152" name="ln-1152" href="#ln-1152"></a><span class="w">    </span><span class="k">end do</span>
+<a id="ln-1153" name="ln-1153" href="#ln-1153"></a><span class="k">    </span><span class="n">alphas_to_try</span><span class="p">(</span><span class="n">n_points</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">me</span><span class="p">%</span><span class="n">alpha_max</span>
+<a id="ln-1154" name="ln-1154" href="#ln-1154"></a>
+<a id="ln-1155" name="ln-1155" href="#ln-1155"></a><span class="w">    </span><span class="c">! now compute the functions at these alphas:</span>
+<a id="ln-1156" name="ln-1156" href="#ln-1156"></a><span class="w">    </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">big</span>
+<a id="ln-1157" name="ln-1157" href="#ln-1157"></a><span class="w">    </span><span class="k">do </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">n_points</span>
+<a id="ln-1158" name="ln-1158" href="#ln-1158"></a>
+<a id="ln-1159" name="ln-1159" href="#ln-1159"></a><span class="w">        </span><span class="n">x_tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">xold</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">p</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">alphas_to_try</span><span class="p">(</span><span class="n">i</span><span class="p">)</span>
+<a id="ln-1160" name="ln-1160" href="#ln-1160"></a>
+<a id="ln-1161" name="ln-1161" href="#ln-1161"></a><span class="w">        </span><span class="c">! evaluate the function at tthis point:</span>
+<a id="ln-1162" name="ln-1162" href="#ln-1162"></a><span class="w">        </span><span class="k">call </span><span class="n">me</span><span class="p">%</span><span class="n">func</span><span class="p">(</span><span class="n">x_tmp</span><span class="p">,</span><span class="n">fvec_tmp</span><span class="p">)</span>
+<a id="ln-1163" name="ln-1163" href="#ln-1163"></a><span class="w">        </span><span class="n">f_tmp</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">norm2</span><span class="p">(</span><span class="n">fvec_tmp</span><span class="p">)</span>
+<a id="ln-1164" name="ln-1164" href="#ln-1164"></a>
+<a id="ln-1165" name="ln-1165" href="#ln-1165"></a><span class="w">        </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">f_tmp</span><span class="o">&lt;=</span><span class="n">f</span><span class="p">)</span><span class="w"> </span><span class="k">then</span><span class="w"> </span><span class="c">! new best point</span>
+<a id="ln-1166" name="ln-1166" href="#ln-1166"></a><span class="w">            </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">x_tmp</span>
+<a id="ln-1167" name="ln-1167" href="#ln-1167"></a><span class="w">            </span><span class="n">f</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">f_tmp</span>
+<a id="ln-1168" name="ln-1168" href="#ln-1168"></a><span class="w">            </span><span class="n">fvec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">fvec_tmp</span>
+<a id="ln-1169" name="ln-1169" href="#ln-1169"></a><span class="w">        </span><span class="k">end if</span>
+<a id="ln-1170" name="ln-1170" href="#ln-1170"></a>
+<a id="ln-1171" name="ln-1171" href="#ln-1171"></a><span class="k">    end do</span>
+<a id="ln-1172" name="ln-1172" href="#ln-1172"></a>
+<a id="ln-1173" name="ln-1173" href="#ln-1173"></a><span class="k">    end subroutine </span><span class="n">fixed_point_linesearch</span>
+<a id="ln-1174" name="ln-1174" href="#ln-1174"></a><span class="c">!*****************************************************************************************</span>
+<a id="ln-1175" name="ln-1175" href="#ln-1175"></a>
+<a id="ln-1176" name="ln-1176" href="#ln-1176"></a><span class="c">!******************************************************************************************************</span>
+<a id="ln-1177" name="ln-1177" href="#ln-1177"></a><span class="w">    </span><span class="k">end module </span><span class="n">nlesolver_module</span>
+<a id="ln-1178" name="ln-1178" href="#ln-1178"></a><span class="c">!******************************************************************************************************</span>
 </pre></div>
 
       </section>
diff --git a/src/nlesolver_module.F90 b/src/nlesolver_module.F90
index 174483a..1de8926 100755
--- a/src/nlesolver_module.F90
+++ b/src/nlesolver_module.F90
@@ -123,7 +123,9 @@ module nlesolver_module
         real(wp) :: damp    = zero  !! damp parameter for LSQR
 
         ! LUSOL parameters:
-        integer :: lusol_method = 0
+        integer :: lusol_method = 0 !! * 0 => TPP: Threshold Partial   Pivoting.
+                                    !! * 1 => TRP: Threshold Rook      Pivoting.
+                                    !! * 2 => TCP: Threshold Complete  Pivoting.
 
         ! dense version:
         procedure(grad_func),pointer :: grad => null() !! user-supplied routine to compute the gradient of the function (dense version)
@@ -377,7 +379,11 @@ subroutine initialize_nlesolver_variables(me,&
     real(wp),intent(in),optional      :: damp    !! `LSQR`: damp factor
     integer,intent(in),optional       :: itnlim  !! `LSQR`: max iterations
     integer,intent(in),optional       :: nout    !! `LSQR`: output unit for printing
-    integer,intent(in),optional       :: lusol_method
+    integer,intent(in),optional       :: lusol_method !! `LUSOL` method:
+                                                      !!
+                                                      !! * 0 => TPP: Threshold Partial   Pivoting.
+                                                      !! * 1 => TRP: Threshold Rook      Pivoting.
+                                                      !! * 2 => TCP: Threshold Complete  Pivoting.
 
     logical :: status_ok !! true if there were no errors
 
@@ -494,12 +500,6 @@ subroutine initialize_nlesolver_variables(me,&
             ! LUSOL method
             if (present(nout)) me%lusol_method = lusol_method
 
-            ! now now, some options are not available for sparse mode
-            !...see if this is possible in sparse mode... TODO
-            if (me%use_broyden) then
-                call me%set_status(istat = -16, string = 'Error: broyden method not available for sparse solver')
-                return
-            end if
         end if
     end if
 
@@ -521,30 +521,34 @@ subroutine nlesolver_solver(me,x)
     class(nlesolver_type),intent(inout) :: me
     real(wp),dimension(:),intent(inout) :: x
 
-    real(wp),dimension(:)  ,allocatable :: fvec            !! function vector
-    real(wp),dimension(:,:),allocatable :: fjac            !! jacobian matrix [dense]
-    real(wp),dimension(:),  allocatable :: fjac_sparse     !! jacobian matrix [sparse]
-    real(wp),dimension(:)  ,allocatable :: rhs             !! linear system right-hand side
-    real(wp),dimension(:)  ,allocatable :: p               !! search direction
-    real(wp),dimension(:)  ,allocatable :: xold            !! previous value of `x`
-    real(wp),dimension(:)  ,allocatable :: prev_fvec       !! previous function vector
-    real(wp),dimension(:,:),allocatable :: prev_fjac       !! previous jacobian matrix
-    real(wp),dimension(:,:),allocatable :: delf            !! used for Broyden (rank 2 for `matmul`)
-    real(wp),dimension(:,:),allocatable :: delx            !! used for Broyden (rank 2 for `matmul`)
-    logical                             :: user_stop       !! user stop button flag
-    integer                             :: info            !! status flag from the [[linear_solver]]
-    integer                             :: iter            !! iteration counter
-    real(wp)                            :: f               !! magnitude of `fvec`
-    real(wp)                            :: fold            !! previous value of `f`
-    integer                             :: n_uphill        !! number of steps taken in the "uphill" direction
-                                                           !! (where `f` is increasing)
-    real(wp)                            :: delxmag2        !! used for Broyden
-    logical                             :: recompute_jac   !! if using Broyden, and we want to call the user
-                                                           !! jacobian routine instead
-    integer                             :: broyden_counter !! number of times the broyden update has been used
-    integer                             :: alloc_stat      !! allocation status flag
+    real(wp),dimension(:)  ,allocatable :: fvec             !! function vector
+    real(wp),dimension(:,:),allocatable :: fjac             !! jacobian matrix [dense]
+    real(wp),dimension(:),  allocatable :: fjac_sparse      !! jacobian matrix [sparse]
+    real(wp),dimension(:),  allocatable :: prev_fjac_sparse !! previous jacobian matrix [sparse]
+    real(wp),dimension(:)  ,allocatable :: rhs              !! linear system right-hand side
+    real(wp),dimension(:)  ,allocatable :: p                !! search direction
+    real(wp),dimension(:)  ,allocatable :: xold             !! previous value of `x`
+    real(wp),dimension(:)  ,allocatable :: prev_fvec        !! previous function vector
+    real(wp),dimension(:,:),allocatable :: prev_fjac        !! previous jacobian matrix
+    real(wp),dimension(:,:),allocatable :: delf             !! used for Broyden (rank 2 for `matmul`)
+    real(wp),dimension(:,:),allocatable :: delx             !! used for Broyden (rank 2 for `matmul`)
+    logical                             :: user_stop        !! user stop button flag
+    integer                             :: info             !! status flag from the [[linear_solver]]
+    integer                             :: iter             !! iteration counter
+    real(wp)                            :: f                !! magnitude of `fvec`
+    real(wp)                            :: fold             !! previous value of `f`
+    integer                             :: n_uphill         !! number of steps taken in the "uphill" direction
+                                                            !! (where `f` is increasing)
+    real(wp)                            :: delxmag2         !! used for Broyden
+    logical                             :: recompute_jac    !! if using Broyden, and we want to call the user
+                                                            !! jacobian routine instead
+    integer                             :: broyden_counter  !! number of times the broyden update has been used
+    integer                             :: alloc_stat       !! allocation status flag
     type(lsqr_solver_ez) :: sparse_solver  !! sparse LSQR solver class
     type(lusol_settings) :: lusol_options
+    integer :: i !! counter
+    integer,dimension(:),allocatable :: idx, index_array !! for sparse indexing
+    character(len=10) :: i_str !! string version of `i` for row string
 
     if (me%istat<0) return ! class was not initialized properly
 
@@ -577,6 +581,7 @@ subroutine nlesolver_solver(me,x)
     else
         ! sparse
         if (alloc_stat==0) allocate(fjac_sparse (me%n_nonzeros) , stat=alloc_stat)
+        if (me%use_broyden .and. alloc_stat==0) allocate(prev_fjac_sparse(me%n_nonzeros) , stat=alloc_stat)
     end if
 
     if (alloc_stat==0) allocate(rhs      (me%m)      , stat=alloc_stat)
@@ -585,7 +590,10 @@ subroutine nlesolver_solver(me,x)
     if (me%use_broyden) then
         ! only need these for broyden:
         if (alloc_stat==0) allocate(prev_fvec(me%m)      , stat=alloc_stat)
-        if (alloc_stat==0) allocate(prev_fjac(me%m,me%n) , stat=alloc_stat)
+        if (me%sparsity_mode/=1 .and. alloc_stat==0) then
+            allocate(prev_fjac(me%m,me%n) , stat=alloc_stat)
+            index_array = [(i, i=1,me%n_nonzeros)] ! an array to index the sparse jacobian elements
+        end if
         if (alloc_stat==0) allocate(delf     (me%m,1)    , stat=alloc_stat)
         if (alloc_stat==0) allocate(delx     (me%n,1)    , stat=alloc_stat)
     end if
@@ -626,7 +634,13 @@ subroutine nlesolver_solver(me,x)
             if (me%use_broyden .and. .not. recompute_jac) then
                 if (iter==1) then
                     ! always compute Jacobian on the first iteration
-                    call me%grad(x,fjac)
+                    !call me%grad(x,fjac)
+                    select case (me%sparsity_mode)
+                    case (1)
+                        call me%grad(x,fjac)
+                    case (2:)
+                        call me%grad_sparse(x,fjac_sparse)
+                    end select
                     broyden_counter = 0
                 else
                     ! and use Broyden update to estimate Jacobian
@@ -635,23 +649,55 @@ subroutine nlesolver_solver(me,x)
                     ! note: fvec was computed the last iteration
                     delx(:,1) = x - xold
                     delf(:,1) = fvec - prev_fvec
-                    delxmag2  = dot_product(delx(:,1),delx(:,1))
 
-                    if (delxmag2 < eps) then
-                        call me%set_status(istat = -8, &
-                                string = 'Error: Divide by zero when computing Broyden update')
-                        exit
-                    end if
+                    if (me%sparsity_mode==1) then ! dense
+
+                        delxmag2 = dot_product(delx(:,1),delx(:,1))
+                        if (delxmag2 < eps) then
+                            call me%set_status(istat = -8, &
+                                    string = 'Error: Divide by zero when computing Broyden update')
+                            exit
+                        end if
+
+                        ! Jacobian estimate:
+                        ! This is the equation from wikipedia : https://en.wikipedia.org/wiki/Broyden%27s_method
+                        fjac = prev_fjac + matmul((delf-matmul(prev_fjac,delx)), transpose(delx)) / delxmag2
 
-                    ! Jacobian estimate:
-                    fjac = prev_fjac + &
-                           matmul((delf-matmul(prev_fjac,delx)),&
-                           transpose(delx))/delxmag2
+                        ! see also: eqn 4 in Schubert, which is different ...
 
+                    else ! using a sparse option
+
+                        ! Just a row-by-row version of the fjac equation above.
+                        ! see L.K. Schubert, 1970
+                        do i = 1, me%m
+
+                            idx = pack(index_array, mask = me%irow==i) ! the nonzero elements in this row
+                            if (size(idx)==0) cycle ! no non-zeros in this row
+
+                            associate (dx => delx(me%icol(idx),:)) ! nonzero x vec for this row
+                                delxmag2 = dot_product(dx(:,1),dx(:,1)) ! only those x's for this row
+                                if (delxmag2 < eps) then
+                                    write(i_str,'(I10)') i
+                                    call me%set_status(istat = -8, &
+                                            string = 'Error: Divide by zero when computing sparse Broyden update for row '//&
+                                            trim(adjustl(i_str)))
+                                    exit
+                                end if
+                                fjac_sparse(idx) = prev_fjac_sparse(idx) + &
+                                        matmul((delf(i,1)-matmul(prev_fjac_sparse(idx),dx)), transpose(dx)) / delxmag2
+                            end associate
+
+                        end do
+
+                    end if
                     broyden_counter = broyden_counter + 1
                 end if
-                prev_fjac = fjac
                 prev_fvec = fvec
+                if (me%sparsity_mode==1) then
+                    prev_fjac = fjac
+                else
+                    prev_fjac_sparse = fjac_sparse
+                end if
             else
                 ! compute the jacobian:
                 select case (me%sparsity_mode)
@@ -698,11 +744,8 @@ subroutine nlesolver_solver(me,x)
             case (3)
                 ! use lusol solver
                 lusol_options%method = me%lusol_method
-                    ! 0    =>  TPP: Threshold Partial   Pivoting.
-                    ! 1    =>  TRP: Threshold Rook      Pivoting.
-                    ! 2    =>  TCP: Threshold Complete  Pivoting.
                 call solve(me%n,me%m,me%n_nonzeros,me%irow,me%icol,fjac_sparse,rhs,p,info,&
-                            settings=lusol_options)
+                           settings=lusol_options)
             end select
 
             ! check for errors:
@@ -982,7 +1025,7 @@ subroutine backtracking_linesearch(me,xold,p,x,f,fvec,fjac,fjac_sparse)
         end if
 
         if (((f - ftmp) / 2.0_wp >= alpha*t) .or. min_alpha_reached) then
-            if (min_alpha_reached) then
+            if (me%verbose .and. min_alpha_reached) then
                 write(me%iunit,'(A)') '        Minimum alpha reached'
             end if
             ! Armijo-Goldstein condition is satisfied
diff --git a/tipuesearch/tipuesearch_content.js b/tipuesearch/tipuesearch_content.js
index 61fbfa0..5a584f9 100644
--- a/tipuesearch/tipuesearch_content.js
+++ b/tipuesearch/tipuesearch_content.js
@@ -1 +1 @@
-var tipuesearch = {"pages":[{"title":" nlesolver-fortran ","text":"nlesolver-fortran Nonlinear Equation Solver with Modern Fortran. A basic Newton-Raphson type nonlinear equation solver for dense systems with m functions of n input variables. A work in progress. Status Features Is object-oriented. Works with square, under-determined, or over-determined systems. Three different methods to solve the linear system: LAPACK routines ( dgesv or dgels ) for dense systems: If n=m , uses dgesv (LU decomposition). If n/=m , uses dgels (if m>n uses QR factorization, if m<n uses LQ factorization). lsqr -- a conjugate-gradient type method for solving sparse linear equations and sparse least-squares problems. lusol -- A sparse LU factorization for square and rectangular matrices, with Bartels-Golub-Reid updates for column replacement and other rank-1 modifications. Has a Broyden update option. Has various line search options. use a specified constant step size (0,1] backtracking linesearch method exact linesearch method using fmin minimizer evaluate function at specified fixed points Compiling A Fortran Package Manager file is also included, so that the library and tests cases can be compiled with FPM. For example: fpm build --profile release\nfpm test --profile release By default, the library is built with double precision ( real64 ) real values. Explicitly specifying the real kind can be done using the following preprocessor flags: Preprocessor flag Kind Number of bytes REAL32 real(kind=real32) 4 REAL64 real(kind=real64) 8 REAL128 real(kind=real128) 16 For example, to build a single precision version of the library, use: fpm build --profile release --flag \"-DREAL32\" To use nlesolver within your fpm project, add the following to your fpm.toml file: [dependencies] nlesolver-fortran = { git = \"https://github.com/jacobwilliams/nlesolver-fortran.git\" } Or to use a specific version: [dependencies] nlesolver-fortran = { git = \"https://github.com/jacobwilliams/nlesolver-fortran.git\" , tag = \"1.1.0\" } Note that LAPACK is required to build. The fmin , lsqr , and lusol libraries are also dependencies (which will be automatically downloaded by fpm). Documentation The API documentation for the current master branch can be found here .  This is generated by processing the source files with FORD . License The NLESolver-Fortran source code and related files and documentation are distributed under a permissive free software license (BSD-3). See also MINPACK -- Modernized Minpack: for solving nonlinear equations and nonlinear least squares problems LUSOL Stanford University Systems Optimization Laboratory qr_mumps -- a software package for the solution of sparse, linear\n  systems on multicore computers. Developer Info Jacob Williams","tags":"home","loc":"index.html"},{"title":"nlesolver_type – nlesolver-fortran ","text":"type, public :: nlesolver_type Nonlinear equations solver class. Components Type Visibility Attributes Name Initial integer, private :: n = 0 number of opt vars integer, private :: m = 0 number of constraints integer, private :: max_iter = 100 maximum number of iterations real(kind=wp), private :: tol = 1.0e-6_wp convergence tolerance for function values real(kind=wp), private :: alpha = 1.0_wp step length (when specified constant) real(kind=wp), private :: alpha_min = 0.1_wp minimum step length (when allowed to vary) real(kind=wp), private :: alpha_max = 1.0_wp maximum step length (when allowed to vary) real(kind=wp), private :: tolx = 1.0e-8_wp convergence tolerance for x real(kind=wp), private :: c = 0.5_wp backtracking linesearch parameter (0,1) real(kind=wp), private :: tau = 0.5_wp backtracking linesearch parameter (0,1) real(kind=wp), private :: fmin_tol = 1.0e-5_wp tolerance for \"exact\" linesearch integer, private :: n_intervals = 2 number of intervals for fixed point linesearch logical, private :: use_broyden = .false. if true, a Broyden update is used\nrather than computing the Jacobian\nat every step. The grad function is\nonly called for the initial evaluation. integer, private :: broyden_update_n = 4 if this value is >0 , the Broyden update\nis computed at most this many times before\nthe full Jacobian is recomputed. integer, private :: n_uphill_max = 5 maximum number of consecutive steps\nto allow where the value of f increases logical, private :: verbose = .false. verbose output printing integer, private :: iunit = output_unit output unit for printing (assumed to be open). character(len=:), private, allocatable :: message latest status message integer, private :: istat = -999 latest status message procedure( func_func ), private, pointer :: func => null() user-supplied routine to compute the function procedure( export_func ), private, pointer :: export_iteration => null() user-supplied routine to export iterations procedure( wait_func ), private, pointer :: user_input_check => null() user-supplied routine to enable user to stop iterations procedure( linesearch_func ), private, pointer :: linesearch => null() line search method (determined by step_mode user input in initialize ) integer, private :: sparsity_mode = 1 sparsity mode: 1 - assume dense (use dense solver) 2 - assume sparse (use LSQR sparse solver). 3 - assume sparse (use LUSOL sparse solver). integer, private :: n_nonzeros = -1 number of nonzero Jacobian elements (used for sparsity_mode > 1 ) integer, private, dimension(:), allocatable :: irow sparsity pattern nonzero elements row indices. integer, private, dimension(:), allocatable :: icol sparsity pattern nonzero elements column indices real(kind=wp), private :: atol = zero relative error in definition of A real(kind=wp), private :: btol = zero relative error in definition of b real(kind=wp), private :: conlim = zero An upper limit on cond(Abar) , the apparent\ncondition number of the matrix Abar . integer, private :: itnlim = 100 max iterations integer, private :: nout = 0 output unit for printing real(kind=wp), private :: damp = zero damp parameter for LSQR integer, private :: lusol_method = 0 procedure( grad_func ), private, pointer :: grad => null() user-supplied routine to compute the gradient of the function (dense version) procedure( grad_func_sparse ), private, pointer :: grad_sparse => null() user-supplied routine to compute the gradient of the function (sparse version) Type-Bound Procedures procedure, public :: initialize => initialize_nlesolver_variables private  subroutine initialize_nlesolver_variables (me, n, m, max_iter, tol, alpha, alpha_min, alpha_max, tolx, fmin_tol, backtrack_c, backtrack_tau, use_broyden, broyden_update_n, step_mode, func, grad, grad_sparse, export_iteration, user_input_check, verbose, iunit, n_uphill_max, n_intervals, sparsity_mode, irow, icol, atol, btol, conlim, damp, itnlim, nout, lusol_method) Constructor for the class. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(in) :: n number of optimization variables integer, intent(in) :: m number of constraints integer, intent(in) :: max_iter maximum number of iterations real(kind=wp), intent(in) :: tol function convergence tolerance real(kind=wp), intent(in), optional :: alpha constant step length for step_mode=1 (0,1] real(kind=wp), intent(in), optional :: alpha_min minimum step length (0,1] real(kind=wp), intent(in), optional :: alpha_max maximum step length (0,1] real(kind=wp), intent(in), optional :: tolx convergence tolerance for changes in x real(kind=wp), intent(in), optional :: fmin_tol convergence tolerance for fmin (used when step_mode=3 ) real(kind=wp), intent(in), optional :: backtrack_c backtracking linesearch parameter (0,1) real(kind=wp), intent(in), optional :: backtrack_tau backtracking linesearch parameter (0,1) logical, intent(in), optional :: use_broyden use a Broyden update (default is False) integer, intent(in), optional :: broyden_update_n For Broyden mode, update the full Jacobian\nat most every this many iterations (must be >1)\nIf <=1 then Jacobian is only computed on the\nfirst iteration. integer, intent(in), optional :: step_mode step mode: Read more… procedure( func_func ) :: func computes the function vector procedure( grad_func ), optional :: grad computes the jacobian [required for dense mode: sparsity_mode=1 ] procedure( grad_func_sparse ), optional :: grad_sparse computes the jacobian [required for sparse mode: sparsity_mode>1 ] procedure( export_func ), optional :: export_iteration function to export each iteration procedure( wait_func ), optional :: user_input_check check for user input (to stop solver if necessary) logical, intent(in), optional :: verbose for verbose status printing integer, intent(in), optional :: iunit unit for verbose printing (assumed to be open).\nby default this is output_unit . integer, intent(in), optional :: n_uphill_max maximum number of consecutive steps\nto allow where the value of f increases integer, intent(in), optional :: n_intervals number of intervals for fixed point linesearch integer, intent(in), optional :: sparsity_mode sparsity mode: Read more… integer, intent(in), optional, dimension(:) :: irow sparsity pattern nonzero elements row indices.\nmust be specified with icol and be the same length ( n_nonzeros ). integer, intent(in), optional, dimension(:) :: icol sparsity pattern nonzero elements column indices\nmust be specified with icol and be the same length ( n_nonzeros ). real(kind=wp), intent(in), optional :: atol LSQR : relative error in definition of A real(kind=wp), intent(in), optional :: btol LSQR : relative error in definition of b real(kind=wp), intent(in), optional :: conlim LSQR : An upper limit on cond(Abar) , the apparent\ncondition number of the matrix Abar . real(kind=wp), intent(in), optional :: damp LSQR : damp factor integer, intent(in), optional :: itnlim LSQR : max iterations integer, intent(in), optional :: nout LSQR : output unit for printing integer, intent(in), optional :: lusol_method procedure, public :: solve => nlesolver_solver private  subroutine nlesolver_solver (me, x) Main solver. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(inout), dimension(:) :: x procedure, public :: destroy => destroy_nlesolver_variables private  subroutine destroy_nlesolver_variables (me) Destructor Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(out) :: me procedure, public :: status => get_status private  subroutine get_status (me, istat, message) Return the status code and message from the nlesolver_type class. Read more… Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(out), optional :: istat Integer status code. character(len=:), intent(out), optional, allocatable :: message Text status message procedure, private :: set_status private  subroutine set_status (me, istat, string, i, r) Set status flag and message. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(in) :: istat status code character(len=*), intent(in) :: string status message integer, intent(in), optional :: i an integer value to append real(kind=wp), intent(in), optional :: r a real value to append Source Code type , public :: nlesolver_type !! Nonlinear equations solver class. private integer :: n = 0 !! number of opt vars integer :: m = 0 !! number of constraints integer :: max_iter = 100 !! maximum number of iterations real ( wp ) :: tol = 1.0e-6_wp !! convergence tolerance for function values real ( wp ) :: alpha = 1.0_wp !! step length (when specified constant) real ( wp ) :: alpha_min = 0.1_wp !! minimum step length (when allowed to vary) real ( wp ) :: alpha_max = 1.0_wp !! maximum step length (when allowed to vary) real ( wp ) :: tolx = 1.0e-8_wp !! convergence tolerance for `x` real ( wp ) :: c = 0.5_wp !! backtracking linesearch parameter (0,1) real ( wp ) :: tau = 0.5_wp !! backtracking linesearch parameter (0,1) real ( wp ) :: fmin_tol = 1.0e-5_wp !! tolerance for \"exact\" linesearch integer :: n_intervals = 2 !! number of intervals for fixed point linesearch logical :: use_broyden = . false . !! if true, a Broyden update is used !! rather than computing the Jacobian !! at every step. The `grad` function is !! only called for the initial evaluation. integer :: broyden_update_n = 4 !! if this value is `>0`, the Broyden update !! is computed at most this many times before !! the full Jacobian is recomputed. integer :: n_uphill_max = 5 !! maximum number of consecutive steps !! to allow where the value of `f` increases logical :: verbose = . false . !! verbose output printing integer :: iunit = output_unit !! output unit for printing (assumed to be open). character ( len = :), allocatable :: message !! latest status message integer :: istat = - 999 !! latest status message procedure ( func_func ), pointer :: func => null () !! user-supplied routine to compute the function procedure ( export_func ), pointer :: export_iteration => null () !! user-supplied routine to export iterations procedure ( wait_func ), pointer :: user_input_check => null () !! user-supplied routine to enable user to stop iterations procedure ( linesearch_func ), pointer :: linesearch => null () !! line search method (determined by `step_mode` user input in [[nlesolver_type:initialize]]) ! sparsity options: integer :: sparsity_mode = 1 !! sparsity mode: !! !! * 1 - assume dense (use dense solver) !! * 2 - assume sparse (use LSQR sparse solver). !! * 3 - assume sparse (use LUSOL sparse solver). integer :: n_nonzeros = - 1 !! number of nonzero Jacobian elements (used for `sparsity_mode > 1`) integer , dimension (:), allocatable :: irow !! sparsity pattern nonzero elements row indices. integer , dimension (:), allocatable :: icol !! sparsity pattern nonzero elements column indices ! LSQR parameters: real ( wp ) :: atol = zero !! relative error in definition of `A` real ( wp ) :: btol = zero !! relative error in definition of `b` real ( wp ) :: conlim = zero !! An upper limit on `cond(Abar)`, the apparent !! condition number of the matrix `Abar`. integer :: itnlim = 100 !! max iterations integer :: nout = 0 !! output unit for printing real ( wp ) :: damp = zero !! damp parameter for LSQR ! LUSOL parameters: integer :: lusol_method = 0 ! dense version: procedure ( grad_func ), pointer :: grad => null () !! user-supplied routine to compute the gradient of the function (dense version) ! sparse version: procedure ( grad_func_sparse ), pointer :: grad_sparse => null () !! user-supplied routine to compute the gradient of the function (sparse version) contains private procedure , public :: initialize => initialize_nlesolver_variables procedure , public :: solve => nlesolver_solver procedure , public :: destroy => destroy_nlesolver_variables procedure , public :: status => get_status procedure :: set_status end type nlesolver_type","tags":"","loc":"type/nlesolver_type.html"},{"title":"func_func – nlesolver-fortran","text":"interface private  subroutine func_func(me, x, f) Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(out), dimension(:) :: f Description compute the function","tags":"","loc":"interface/func_func.html"},{"title":"grad_func – nlesolver-fortran","text":"interface private  subroutine grad_func(me, x, g) Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(out), dimension(:,:) :: g Description compute the gradient of the function (Jacobian). Dense version.","tags":"","loc":"interface/grad_func.html"},{"title":"grad_func_sparse – nlesolver-fortran","text":"interface private  subroutine grad_func_sparse(me, x, g) Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(out), dimension(:) :: g sparse jacobian. length is n_nonzeros Description compute the gradient of the function (Jacobian). Sparse version.","tags":"","loc":"interface/grad_func_sparse.html"},{"title":"export_func – nlesolver-fortran","text":"interface private  subroutine export_func(me, x, f, iter) Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(in), dimension(:) :: f integer, intent(in) :: iter iteration number Description export an iteration:","tags":"","loc":"interface/export_func.html"},{"title":"wait_func – nlesolver-fortran","text":"interface private  subroutine wait_func(me, user_stop) Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me logical, intent(out) :: user_stop Description enable a user-triggered stop of the iterations:","tags":"","loc":"interface/wait_func.html"},{"title":"linesearch_func – nlesolver-fortran","text":"interface private  subroutine linesearch_func(me, xold, p, x, f, fvec, fjac, fjac_sparse) Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f input: current magnitude of fvec , output: new value of f real(kind=wp), intent(inout), dimension(me%m) :: fvec input: current function vector, output: new function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] Description line search method. Note that not all inputs/outputs are\nused by all methods.","tags":"","loc":"interface/linesearch_func.html"},{"title":"set_status – nlesolver-fortran","text":"private  subroutine set_status(me, istat, string, i, r) Set status flag and message. Type Bound nlesolver_type Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(in) :: istat status code character(len=*), intent(in) :: string status message integer, intent(in), optional :: i an integer value to append real(kind=wp), intent(in), optional :: r a real value to append Called by proc~~set_status~~CalledByGraph proc~set_status nlesolver_module::nlesolver_type%set_status proc~initialize_nlesolver_variables nlesolver_module::nlesolver_type%initialize_nlesolver_variables proc~initialize_nlesolver_variables->proc~set_status proc~nlesolver_solver nlesolver_module::nlesolver_type%nlesolver_solver proc~nlesolver_solver->proc~set_status Help Graph Key Nodes of different colours represent the following: Graph Key Subroutine Subroutine Function Function Interface Interface Type Bound Procedure Type Bound Procedure Unknown Procedure Type Unknown Procedure Type Program Program This Page's Entity This Page's Entity Solid arrows point from a procedure to one which it calls. Dashed \narrows point from an interface to procedures which implement that interface.\nThis could include the module procedures in a generic interface or the\nimplementation in a submodule of an interface in a parent module. Source Code subroutine set_status ( me , istat , string , i , r ) implicit none class ( nlesolver_type ), intent ( inout ) :: me integer , intent ( in ) :: istat !! status code character ( len =* ), intent ( in ) :: string !! status message integer , intent ( in ), optional :: i !! an integer value to append real ( wp ), intent ( in ), optional :: r !! a real value to append character ( len = 256 ) :: numstr !! for number fo string conversion character ( len = :), allocatable :: message !! the full message to log integer :: iostat !! write `iostat` code message = trim ( string ) if ( present ( i )) then numstr = '' write ( numstr , fmt =* , iostat = iostat ) i if ( iostat /= 0 ) numstr = '****' message = message // ' ' // trim ( adjustl ( numstr )) end if if ( present ( r )) then numstr = '' write ( numstr , fmt =* , iostat = iostat ) r if ( iostat /= 0 ) numstr = '****' message = message // ' ' // trim ( adjustl ( numstr )) end if if ( me % verbose ) then write ( me % iunit , '(A)' , iostat = iostat ) message end if ! store in the class: me % istat = istat me % message = message end subroutine set_status","tags":"","loc":"proc/set_status.html"},{"title":"get_status – nlesolver-fortran","text":"private  subroutine get_status(me, istat, message) Return the status code and message from the nlesolver_type class. Status codes -1   -- Error: Invalid alpha -2   -- Error: Invalid alpha_min -3   -- Error: Invalid alpha_max -4   -- Error: Alpha_min must be < alpha_max -5   -- Error: Invalid step_mode -6   -- Error solving linear system -7   -- Error: More than 5 steps in the uphill direction -8   -- Error: Divide by zero when computing Broyden update -9   -- Error: Out of memory -10  -- Error: function routine is not associated -11  -- Error: gradient routine is not associated -12  -- Error: backtracking linesearch c must be in range (0, 1) -13  -- Error: backtracking linesearch tau must be in range (0, 1) -14  -- Error: must specify grad_sparse, irow, and icol for sparsity_mode > 1 -15  -- Error: irow and icol must be the same length -999 -- Error: class has not been initialized 0    -- Class successfully initialized in initialize 1    -- Required accuracy achieved 2    -- Solution cannot be improved 3    -- Maximum number of iterations reached 4    -- Stopped by the user Type Bound nlesolver_type Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(out), optional :: istat Integer status code. character(len=:), intent(out), optional, allocatable :: message Text status message Source Code subroutine get_status ( me , istat , message ) implicit none class ( nlesolver_type ), intent ( inout ) :: me integer , intent ( out ), optional :: istat !! Integer status code. character ( len = :), allocatable , intent ( out ), optional :: message !! Text status message if ( present ( istat )) istat = me % istat if ( present ( message )) then if ( allocated ( me % message )) then message = trim ( me % message ) else message = 'Error: class has not been initialized' end if end if end subroutine get_status","tags":"","loc":"proc/get_status.html"},{"title":"initialize_nlesolver_variables – nlesolver-fortran","text":"private  subroutine initialize_nlesolver_variables(me, n, m, max_iter, tol, alpha, alpha_min, alpha_max, tolx, fmin_tol, backtrack_c, backtrack_tau, use_broyden, broyden_update_n, step_mode, func, grad, grad_sparse, export_iteration, user_input_check, verbose, iunit, n_uphill_max, n_intervals, sparsity_mode, irow, icol, atol, btol, conlim, damp, itnlim, nout, lusol_method) Constructor for the class. Type Bound nlesolver_type Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(in) :: n number of optimization variables integer, intent(in) :: m number of constraints integer, intent(in) :: max_iter maximum number of iterations real(kind=wp), intent(in) :: tol function convergence tolerance real(kind=wp), intent(in), optional :: alpha constant step length for step_mode=1 (0,1] real(kind=wp), intent(in), optional :: alpha_min minimum step length (0,1] real(kind=wp), intent(in), optional :: alpha_max maximum step length (0,1] real(kind=wp), intent(in), optional :: tolx convergence tolerance for changes in x real(kind=wp), intent(in), optional :: fmin_tol convergence tolerance for fmin (used when step_mode=3 ) real(kind=wp), intent(in), optional :: backtrack_c backtracking linesearch parameter (0,1) real(kind=wp), intent(in), optional :: backtrack_tau backtracking linesearch parameter (0,1) logical, intent(in), optional :: use_broyden use a Broyden update (default is False) integer, intent(in), optional :: broyden_update_n For Broyden mode, update the full Jacobian\nat most every this many iterations (must be >1)\nIf <=1 then Jacobian is only computed on the\nfirst iteration. integer, intent(in), optional :: step_mode step mode: 1 = use the specified alpha (0,1] 2 = backtracking linesearch (between alpha_min and alpha_max ) 3 = exact linesearch (between alpha_min and alpha_max ) 4 = evaluate function at specified fixed points  (between alpha_min and alpha_max ) procedure( func_func ) :: func computes the function vector procedure( grad_func ), optional :: grad computes the jacobian [required for dense mode: sparsity_mode=1 ] procedure( grad_func_sparse ), optional :: grad_sparse computes the jacobian [required for sparse mode: sparsity_mode>1 ] procedure( export_func ), optional :: export_iteration function to export each iteration procedure( wait_func ), optional :: user_input_check check for user input (to stop solver if necessary) logical, intent(in), optional :: verbose for verbose status printing integer, intent(in), optional :: iunit unit for verbose printing (assumed to be open).\nby default this is output_unit . integer, intent(in), optional :: n_uphill_max maximum number of consecutive steps\nto allow where the value of f increases integer, intent(in), optional :: n_intervals number of intervals for fixed point linesearch integer, intent(in), optional :: sparsity_mode sparsity mode: 1 - assume dense (use dense solver)\n  Must specify grad for this mode. 2 - assume sparse (use LSQR sparse solver). 3 - assume sparse (use LUSOL sparse solver).\nMust also specify grad_sparse and the irow and icol sparsity pattern for mode>1 . integer, intent(in), optional, dimension(:) :: irow sparsity pattern nonzero elements row indices.\nmust be specified with icol and be the same length ( n_nonzeros ). integer, intent(in), optional, dimension(:) :: icol sparsity pattern nonzero elements column indices\nmust be specified with icol and be the same length ( n_nonzeros ). real(kind=wp), intent(in), optional :: atol LSQR : relative error in definition of A real(kind=wp), intent(in), optional :: btol LSQR : relative error in definition of b real(kind=wp), intent(in), optional :: conlim LSQR : An upper limit on cond(Abar) , the apparent\ncondition number of the matrix Abar . real(kind=wp), intent(in), optional :: damp LSQR : damp factor integer, intent(in), optional :: itnlim LSQR : max iterations integer, intent(in), optional :: nout LSQR : output unit for printing integer, intent(in), optional :: lusol_method Calls proc~~initialize_nlesolver_variables~~CallsGraph proc~initialize_nlesolver_variables nlesolver_module::nlesolver_type%initialize_nlesolver_variables proc~set_status nlesolver_module::nlesolver_type%set_status proc~initialize_nlesolver_variables->proc~set_status Help Graph Key Nodes of different colours represent the following: Graph Key Subroutine Subroutine Function Function Interface Interface Type Bound Procedure Type Bound Procedure Unknown Procedure Type Unknown Procedure Type Program Program This Page's Entity This Page's Entity Solid arrows point from a procedure to one which it calls. Dashed \narrows point from an interface to procedures which implement that interface.\nThis could include the module procedures in a generic interface or the\nimplementation in a submodule of an interface in a parent module. Source Code subroutine initialize_nlesolver_variables ( me ,& n , m , max_iter , tol , alpha , alpha_min , alpha_max , tolx , fmin_tol ,& backtrack_c , backtrack_tau ,& use_broyden , broyden_update_n , step_mode ,& func , grad , grad_sparse ,& export_iteration , user_input_check ,& verbose , iunit , n_uphill_max , n_intervals ,& sparsity_mode , irow , icol ,& atol , btol , conlim , damp , itnlim , nout ,& lusol_method ) implicit none class ( nlesolver_type ), intent ( inout ) :: me integer , intent ( in ) :: n !! number of optimization variables integer , intent ( in ) :: m !! number of constraints integer , intent ( in ) :: max_iter !! maximum number of iterations real ( wp ), intent ( in ) :: tol !! function convergence tolerance procedure ( func_func ) :: func !! computes the function vector procedure ( grad_func ), optional :: grad !! computes the jacobian [required for dense mode: `sparsity_mode=1`] procedure ( grad_func_sparse ), optional :: grad_sparse !! computes the jacobian [required for sparse mode: `sparsity_mode>1`] integer , intent ( in ), optional :: step_mode !! step mode: !! !!  * 1 = use the specified `alpha` (0,1] !!  * 2 = backtracking linesearch (between `alpha_min` and `alpha_max`) !!  * 3 = exact linesearch (between `alpha_min` and `alpha_max`) !!  * 4 = evaluate function at specified fixed points  (between `alpha_min` and `alpha_max`) real ( wp ), intent ( in ), optional :: alpha !! constant step length for `step_mode=1` (0,1] real ( wp ), intent ( in ), optional :: alpha_min !! minimum step length (0,1] real ( wp ), intent ( in ), optional :: alpha_max !! maximum step length (0,1] real ( wp ), intent ( in ), optional :: tolx !! convergence tolerance for changes in `x` real ( wp ), intent ( in ), optional :: fmin_tol !! convergence tolerance for [[fmin]] (used when `step_mode=3`) real ( wp ), intent ( in ), optional :: backtrack_c !! backtracking linesearch parameter (0,1) real ( wp ), intent ( in ), optional :: backtrack_tau !! backtracking linesearch parameter (0,1) logical , intent ( in ), optional :: use_broyden !! use a Broyden update (default is False) integer , intent ( in ), optional :: broyden_update_n !! For Broyden mode, update the full Jacobian !! at most every this many iterations (must be >1) !! If <=1 then Jacobian is only computed on the !! first iteration. procedure ( export_func ), optional :: export_iteration !! function to export each iteration procedure ( wait_func ), optional :: user_input_check !! check for user input (to stop solver if necessary) logical , intent ( in ), optional :: verbose !! for verbose status printing integer , intent ( in ), optional :: iunit !! unit for verbose printing (assumed to be open). !! by default this is `output_unit`. integer , intent ( in ), optional :: n_uphill_max !! maximum number of consecutive steps !! to allow where the value of `f` increases integer , intent ( in ), optional :: n_intervals !! number of intervals for fixed point linesearch integer , intent ( in ), optional :: sparsity_mode !! sparsity mode: !! !! * 1 - assume dense (use dense solver) !!   Must specify `grad` for this mode. !! * 2 - assume sparse (use LSQR sparse solver). !! * 3 - assume sparse (use LUSOL sparse solver). !! Must also specify `grad_sparse` and the `irow` and `icol` !! sparsity pattern for `mode>1`. integer , dimension (:), intent ( in ), optional :: irow !! sparsity pattern nonzero elements row indices. !! must be specified with `icol` and be the same length (`n_nonzeros`). integer , dimension (:), intent ( in ), optional :: icol !! sparsity pattern nonzero elements column indices !! must be specified with `icol` and be the same length (`n_nonzeros`). real ( wp ), intent ( in ), optional :: atol !! `LSQR`: relative error in definition of `A` real ( wp ), intent ( in ), optional :: btol !! `LSQR`: relative error in definition of `b` real ( wp ), intent ( in ), optional :: conlim !! `LSQR`: An upper limit on `cond(Abar)`, the apparent !! condition number of the matrix `Abar`. real ( wp ), intent ( in ), optional :: damp !! `LSQR`: damp factor integer , intent ( in ), optional :: itnlim !! `LSQR`: max iterations integer , intent ( in ), optional :: nout !! `LSQR`: output unit for printing integer , intent ( in ), optional :: lusol_method logical :: status_ok !! true if there were no errors status_ok = . true . !required: me % n = abs ( n ) me % m = abs ( m ) me % max_iter = abs ( max_iter ) me % tol = abs ( tol ) me % func => func if ( present ( grad )) me % grad => grad if ( present ( grad_sparse )) me % grad_sparse => grad_sparse !optional: if ( present ( step_mode )) then select case ( step_mode ) case ( 1 ) ! = use the specified `alpha` (0,1] me % linesearch => simple_step case ( 2 ) ! = backtracking linesearch (between `alpha_min` and `alpha_max`) me % linesearch => backtracking_linesearch case ( 3 ) ! = exact linesearch (between `alpha_min` and `alpha_max`) me % linesearch => exact_linesearch case ( 4 ) ! = evaluate function at specified fixed points (between `alpha_min` and `alpha_max`) me % linesearch => fixed_point_linesearch case default status_ok = . false . call me % set_status ( istat = - 5 , string = 'Error: invalid step_mode:' , i = step_mode ) return end select else me % linesearch => simple_step end if if ( present ( alpha )) me % alpha = abs ( alpha ) if ( present ( alpha_min )) me % alpha_min = abs ( alpha_min ) if ( present ( alpha_max )) me % alpha_max = abs ( alpha_max ) if ( present ( tolx )) me % tolx = abs ( tolx ) if ( present ( backtrack_c )) me % c = abs ( backtrack_c ) if ( present ( backtrack_tau )) me % tau = abs ( backtrack_tau ) if ( present ( use_broyden )) me % use_broyden = use_broyden if ( present ( broyden_update_n )) me % broyden_update_n = abs ( broyden_update_n ) if ( present ( verbose )) me % verbose = verbose if ( present ( iunit )) me % iunit = iunit if ( present ( n_uphill_max )) me % n_uphill_max = abs ( n_uphill_max ) if ( present ( n_intervals )) me % n_intervals = max ( abs ( n_intervals ), 1 ) if ( present ( fmin_tol )) me % fmin_tol = abs ( fmin_tol ) if ( present ( export_iteration )) me % export_iteration => export_iteration if ( present ( user_input_check )) me % user_input_check => user_input_check ! error checks: if ( me % alpha < zero . or . me % alpha > one ) then status_ok = . false . call me % set_status ( istat = - 1 , string = 'Error: invalid alpha:' , r = me % alpha ) return end if if ( me % alpha_min < zero . or . me % alpha_min > one ) then status_ok = . false . call me % set_status ( istat = - 2 , string = 'Error: invalid alpha_min:' , r = me % alpha_min ) return end if if ( me % alpha_max < zero . or . me % alpha_max > one ) then status_ok = . false . call me % set_status ( istat = - 3 , string = 'Error: invalid alpha_max:' , r = me % alpha_max ) return end if if ( me % alpha_max <= me % alpha_min ) then status_ok = . false . call me % set_status ( istat = - 4 , string = 'Error: alpha_min must be < alpha_max' ) return end if if ( me % c < zero . or . me % c > one ) then status_ok = . false . call me % set_status ( istat = - 12 , string = 'Error: backtracking linesearch c must be in range (0, 1):' , r = me % c ) return end if if ( me % tau < zero . or . me % tau > one ) then status_ok = . false . call me % set_status ( istat = - 13 , string = 'Error: backtracking linesearch tau must be in range (0, 1):' , r = me % tau ) return end if ! initialize: me % n_nonzeros = - 1 ! not used if ( allocated ( me % irow )) deallocate ( me % irow ) if ( allocated ( me % icol )) deallocate ( me % icol ) if ( present ( sparsity_mode )) then me % sparsity_mode = sparsity_mode if ( sparsity_mode > 1 ) then ! sparse solver method if ( present ( irow ) . and . present ( icol ) . and . present ( grad_sparse )) then if ( size ( irow ) == size ( icol )) then me % n_nonzeros = size ( irow ) me % irow = irow me % icol = icol else call me % set_status ( istat = - 15 , string = 'Error: irow and icol must be the same length' ) return end if else call me % set_status ( istat = - 14 , string = 'Error: must specify grad_sparse, irow, and icol for sparsity_mode > 1' ) return end if ! LSQR optional inputs: if ( present ( atol )) me % atol = atol if ( present ( btol )) me % btol = btol if ( present ( conlim )) me % conlim = conlim if ( present ( damp )) me % damp = damp if ( present ( itnlim )) me % itnlim = itnlim if ( present ( nout )) me % nout = nout ! LUSOL method if ( present ( nout )) me % lusol_method = lusol_method ! now now, some options are not available for sparse mode !...see if this is possible in sparse mode... TODO if ( me % use_broyden ) then call me % set_status ( istat = - 16 , string = 'Error: broyden method not available for sparse solver' ) return end if end if end if if ( status_ok ) then call me % set_status ( istat = 0 , string = 'Class successfully initialized' ) end if end subroutine initialize_nlesolver_variables","tags":"","loc":"proc/initialize_nlesolver_variables.html"},{"title":"nlesolver_solver – nlesolver-fortran","text":"private  subroutine nlesolver_solver(me, x) Main solver. Type Bound nlesolver_type Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(inout), dimension(:) :: x Calls proc~~nlesolver_solver~~CallsGraph proc~nlesolver_solver nlesolver_module::nlesolver_type%nlesolver_solver initialize initialize proc~nlesolver_solver->initialize proc~linear_solver nlesolver_module::linear_solver proc~nlesolver_solver->proc~linear_solver proc~set_status nlesolver_module::nlesolver_type%set_status proc~nlesolver_solver->proc~set_status solve solve proc~nlesolver_solver->solve Help Graph Key Nodes of different colours represent the following: Graph Key Subroutine Subroutine Function Function Interface Interface Type Bound Procedure Type Bound Procedure Unknown Procedure Type Unknown Procedure Type Program Program This Page's Entity This Page's Entity Solid arrows point from a procedure to one which it calls. Dashed \narrows point from an interface to procedures which implement that interface.\nThis could include the module procedures in a generic interface or the\nimplementation in a submodule of an interface in a parent module. Source Code subroutine nlesolver_solver ( me , x ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension (:), intent ( inout ) :: x real ( wp ), dimension (:) , allocatable :: fvec !! function vector real ( wp ), dimension (:,:), allocatable :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), allocatable :: fjac_sparse !! jacobian matrix [sparse] real ( wp ), dimension (:) , allocatable :: rhs !! linear system right-hand side real ( wp ), dimension (:) , allocatable :: p !! search direction real ( wp ), dimension (:) , allocatable :: xold !! previous value of `x` real ( wp ), dimension (:) , allocatable :: prev_fvec !! previous function vector real ( wp ), dimension (:,:), allocatable :: prev_fjac !! previous jacobian matrix real ( wp ), dimension (:,:), allocatable :: delf !! used for Broyden (rank 2 for `matmul`) real ( wp ), dimension (:,:), allocatable :: delx !! used for Broyden (rank 2 for `matmul`) logical :: user_stop !! user stop button flag integer :: info !! status flag from the [[linear_solver]] integer :: iter !! iteration counter real ( wp ) :: f !! magnitude of `fvec` real ( wp ) :: fold !! previous value of `f` integer :: n_uphill !! number of steps taken in the \"uphill\" direction !! (where `f` is increasing) real ( wp ) :: delxmag2 !! used for Broyden logical :: recompute_jac !! if using Broyden, and we want to call the user !! jacobian routine instead integer :: broyden_counter !! number of times the broyden update has been used integer :: alloc_stat !! allocation status flag type ( lsqr_solver_ez ) :: sparse_solver !! sparse LSQR solver class type ( lusol_settings ) :: lusol_options if ( me % istat < 0 ) return ! class was not initialized properly if (. not . associated ( me % func )) then call me % set_status ( istat = - 10 , string = 'Error: function routine is not associated' ) return end if if ( me % sparsity_mode == 1 . and . . not . associated ( me % grad )) then call me % set_status ( istat = - 11 , string = 'Error: gradient routine is not associated' ) return end if if ( me % sparsity_mode > 1 . and . . not . associated ( me % grad_sparse )) then call me % set_status ( istat = - 11 , string = 'Error: gradient routine is not associated' ) return end if ! initialize: iter = 0 n_uphill = 0 recompute_jac = . false . broyden_counter = 0 ! allocate the arrays: alloc_stat = 0 if ( alloc_stat == 0 ) allocate ( fvec ( me % m ) , stat = alloc_stat ) if ( me % sparsity_mode == 1 ) then ! dense if ( alloc_stat == 0 ) allocate ( fjac ( me % m , me % n ) , stat = alloc_stat ) else ! sparse if ( alloc_stat == 0 ) allocate ( fjac_sparse ( me % n_nonzeros ) , stat = alloc_stat ) end if if ( alloc_stat == 0 ) allocate ( rhs ( me % m ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( p ( me % n ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( xold ( me % n ) , stat = alloc_stat ) if ( me % use_broyden ) then ! only need these for broyden: if ( alloc_stat == 0 ) allocate ( prev_fvec ( me % m ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( prev_fjac ( me % m , me % n ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( delf ( me % m , 1 ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( delx ( me % n , 1 ) , stat = alloc_stat ) end if if ( alloc_stat /= 0 ) then call me % set_status ( istat = - 9 , string = 'Error: Out of memory' ) return else me % istat = - 998 me % message = 'Unknown error' end if ! evaluate the function: call me % func ( x , fvec ) f = norm2 ( fvec ) ! check to see if initial guess is a root: if ( f <= me % tol ) then call me % set_status ( istat = 1 , string = 'Required accuracy achieved' ) else ! main iteration loop: do iter = 1 , me % max_iter ! Export the current iteration: if ( associated ( me % export_iteration )) call me % export_iteration ( x , fvec , iter ) ! Check for user stop: if ( associated ( me % user_input_check )) then call me % user_input_check ( user_stop ) if ( user_stop ) then call me % set_status ( istat = 4 , string = 'Stopped by the user' ) exit end if end if if ( me % use_broyden . and . . not . recompute_jac ) then if ( iter == 1 ) then ! always compute Jacobian on the first iteration call me % grad ( x , fjac ) broyden_counter = 0 else ! and use Broyden update to estimate Jacobian ! for subsequent iterations. ! note: fvec was computed the last iteration delx (:, 1 ) = x - xold delf (:, 1 ) = fvec - prev_fvec delxmag2 = dot_product ( delx (:, 1 ), delx (:, 1 )) if ( delxmag2 < eps ) then call me % set_status ( istat = - 8 , & string = 'Error: Divide by zero when computing Broyden update' ) exit end if ! Jacobian estimate: fjac = prev_fjac + & matmul (( delf - matmul ( prev_fjac , delx )),& transpose ( delx )) / delxmag2 broyden_counter = broyden_counter + 1 end if prev_fjac = fjac prev_fvec = fvec else ! compute the jacobian: select case ( me % sparsity_mode ) case ( 1 ) call me % grad ( x , fjac ) case ( 2 :) call me % grad_sparse ( x , fjac_sparse ) end select recompute_jac = . false . ! for broyden broyden_counter = 0 end if xold = x fold = f ! compute the search direction p by solving linear system: rhs = - fvec ! RHS of the linear system select case ( me % sparsity_mode ) case ( 1 ) ! use dense solver call linear_solver ( me % m , me % n , fjac , rhs , p , info ) case ( 2 ) ! initialize the LSQR sparse solver call sparse_solver % initialize ( me % m , me % n , fjac_sparse , me % irow , me % icol ,& atol = me % atol , & btol = me % btol , & conlim = me % conlim , & itnlim = me % itnlim , & nout = me % nout ) call sparse_solver % solve ( rhs , me % damp , p , info ) ! solve the linear system ! check convergence: select case ( info ) case ( 4 ) call me % set_status ( istat = - 1004 , & string = 'LSQR Error: The system appears to be ill-conditioned. istop =' , i = info ) exit case ( 5 ) call me % set_status ( istat = - 1005 , & string = 'LSQR Error: The iteration limit was reached. istop =' , i = info ) exit case default info = 0 end select case ( 3 ) ! use lusol solver lusol_options % method = me % lusol_method ! 0    =>  TPP: Threshold Partial   Pivoting. ! 1    =>  TRP: Threshold Rook      Pivoting. ! 2    =>  TCP: Threshold Complete  Pivoting. call solve ( me % n , me % m , me % n_nonzeros , me % irow , me % icol , fjac_sparse , rhs , p , info ,& settings = lusol_options ) end select ! check for errors: if ( info /= 0 ) then call me % set_status ( istat = - 6 , string = 'Error solving linear system. info =' , i = info ) exit else ! next step, using the specified method: call me % linesearch ( xold , p , x , f , fvec , fjac , fjac_sparse ) ! keep track of the number of steps in the \"uphill\" direction: if ( f > fold ) then n_uphill = n_uphill + 1 else n_uphill = 0 end if ! check for stopping conditions if ( f <= me % tol ) then call me % set_status ( istat = 1 , string = 'Required accuracy achieved' ) exit elseif ( maxval ( abs ( x - xold )) <= me % tolx ) then call me % set_status ( istat = 2 , string = 'Solution cannot be improved' ) exit elseif ( iter == me % max_iter ) then call me % set_status ( istat = 3 , string = 'Maximum number of iterations reached' ) exit elseif ( n_uphill > me % n_uphill_max ) then call me % set_status ( istat = 5 , string = 'Too many steps in the uphill direction' ) exit elseif ( me % use_broyden ) then ! If delxmag2 is too small when using broyden, just ! call the user-supplied jacobian function to avoid ! a divide by zero on the next step. This should ! normally only happen when the solution is almost converged. if ( norm2 ( x - xold ) ** 2 <= eps ) then recompute_jac = . true . else if ( me % broyden_update_n > 0 ) then ! Note that we also recompute if we have taken an uphill step if ( broyden_counter == me % broyden_update_n . or . n_uphill > 0 ) then ! time to recompute the full jacobian recompute_jac = . true . end if end if end if endif end if end do !end of iterations loop end if !Export the last iteration: iter = iter + 1 if ( associated ( me % export_iteration )) call me % export_iteration ( x , fvec , iter ) end subroutine nlesolver_solver","tags":"","loc":"proc/nlesolver_solver.html"},{"title":"destroy_nlesolver_variables – nlesolver-fortran","text":"private  subroutine destroy_nlesolver_variables(me) Destructor Type Bound nlesolver_type Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(out) :: me Source Code subroutine destroy_nlesolver_variables ( me ) implicit none class ( nlesolver_type ), intent ( out ) :: me me % message = 'Error: class has not been initialized' me % istat = - 999 end subroutine destroy_nlesolver_variables","tags":"","loc":"proc/destroy_nlesolver_variables.html"},{"title":"linear_solver – nlesolver-fortran","text":"private  subroutine linear_solver(m, n, a, b, x, info) Solve the linear system: , using a dense, direct method. if n=m : use LAPACK dgesv (LU decomposition) if n/=m : use LAPACK dgels (if m>n uses QR factorization,\n  if m<n uses LQ factorization) Arguments Type Intent Optional Attributes Name integer, intent(in) :: m number of rows in a integer, intent(in) :: n number of columns in a real(kind=wp), intent(in), dimension(m,n) :: a A matrix of the linear system real(kind=wp), intent(in), dimension(m) :: b RHS of the linear system real(kind=wp), intent(out), dimension(n) :: x the solution of the linear system. integer, intent(out) :: info output status flag ( =0 if success) Called by proc~~linear_solver~~CalledByGraph proc~linear_solver nlesolver_module::linear_solver proc~nlesolver_solver nlesolver_module::nlesolver_type%nlesolver_solver proc~nlesolver_solver->proc~linear_solver Help Graph Key Nodes of different colours represent the following: Graph Key Subroutine Subroutine Function Function Interface Interface Type Bound Procedure Type Bound Procedure Unknown Procedure Type Unknown Procedure Type Program Program This Page's Entity This Page's Entity Solid arrows point from a procedure to one which it calls. Dashed \narrows point from an interface to procedures which implement that interface.\nThis could include the module procedures in a generic interface or the\nimplementation in a submodule of an interface in a parent module. Source Code subroutine linear_solver ( m , n , a , b , x , info ) implicit none integer , intent ( in ) :: n !! number of columns in `a` integer , intent ( in ) :: m !! number of rows in `a` real ( wp ), dimension ( m , n ), intent ( in ) :: a !! `A` matrix of the linear system real ( wp ), dimension ( m ), intent ( in ) :: b !! RHS of the linear system real ( wp ), dimension ( n ), intent ( out ) :: x !! the solution of the linear system. integer , intent ( out ) :: info !! output status flag (`=0` if success) ! LAPACK routine interfaces: interface subroutine dgesv ( n , nrhs , a , lda , ipiv , b , ldb , info ) !! See: [?gesv](https://www.intel.com/content/www/us/en/develop/documentation/onemkl-developer-reference-fortran/top/lapack-routines/lapack-linear-equation-routines/lapack-linear-equation-driver-routines/gesv.html) import :: wp implicit none integer :: info integer :: lda integer :: ldb integer :: n integer :: nrhs integer :: ipiv ( * ) real ( wp ) :: a ( lda , * ) real ( wp ) :: b ( ldb , * ) end subroutine dgesv subroutine dgels ( trans , m , n , nrhs , a , lda , b , ldb , work , lwork , info ) !! See: [?gels](https://www.intel.com/content/www/us/en/develop/documentation/onemkl-developer-reference-fortran/top/lapack-routines/lapack-least-squares-and-eigenvalue-problem/lapack-least-squares-eigenvalue-problem-driver/linear-least-squares-lls-problems-lapack-driver/gels.html) import :: wp implicit none character :: trans integer :: info integer :: lda integer :: ldb integer :: lwork integer :: m integer :: n integer :: nrhs real ( wp ) :: a ( lda , * ) real ( wp ) :: b ( ldb , * ) real ( wp ) :: work ( * ) end subroutine dgels end interface integer , dimension (:), allocatable :: ipiv !! pivot indices array real ( wp ), dimension (:,:), allocatable :: bmat !! copy of `b` so it won't be overwritten real ( wp ), dimension (:), allocatable :: work !! work array for `dgels` real ( wp ), dimension (:,:), allocatable :: amat !! copy of `a` so it won't be overwritten integer :: lwork !! size of `work` allocate ( amat ( m , n )) allocate ( bmat ( max ( 1 , m , n ), 1 )) if ( n == m ) then !normal inverse allocate ( ipiv ( n )) amat = a bmat ( 1 : n , 1 ) = b call dgesv ( n , 1 , amat , n , ipiv , bmat , n , info ) x = bmat ( 1 : n , 1 ) else amat = a bmat = zero bmat ( 1 : m , 1 ) = b lwork = min ( m , n ) + max ( 1 , m , n ) allocate ( work ( lwork )) call dgels ( 'N' , m , n , 1 , amat , m , bmat , max ( 1 , m , n ), work , lwork , info ) x = bmat ( 1 : n , 1 ) end if end subroutine linear_solver","tags":"","loc":"proc/linear_solver.html"},{"title":"simple_step – nlesolver-fortran","text":"private  subroutine simple_step(me, xold, p, x, f, fvec, fjac, fjac_sparse) Take a simple step in the search direction of p * alpha . Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] Source Code subroutine simple_step ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] x = xold + p * me % alpha !evaluate the function at the new point: call me % func ( x , fvec ) f = norm2 ( fvec ) end subroutine simple_step","tags":"","loc":"proc/simple_step.html"},{"title":"backtracking_linesearch – nlesolver-fortran","text":"private  subroutine backtracking_linesearch(me, xold, p, x, f, fvec, fjac, fjac_sparse) Backtracking line search. See also Backtracking line search Note Either fjac or fjac_sparse should be present. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] Source Code subroutine backtracking_linesearch ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] integer :: i !! counter real ( wp ) :: slope !! local slope of the function of `alpha` along the search direction used for line search logical :: min_alpha_reached !! if the minimum step size is reached during the line search real ( wp ) :: alpha !! `alpha` for the line search real ( wp ) :: ftmp !! `f` value for linesearch real ( wp ) :: t !! used for line search real ( wp ), dimension (:), allocatable :: gradf !! line search objective function gradient vector real ( wp ), dimension (:), allocatable :: xtmp !! `x` value for linesearch real ( wp ), dimension (:), allocatable :: fvectmp !! `fvec` value for linesearch ! allocate arrays: allocate ( gradf ( me % n )) allocate ( xtmp ( me % n )) allocate ( fvectmp ( me % m )) ! compute the gradient of the function to be minimized ! (which in this case is 1/2 the norm of fvec). Use the chain ! rule and the Jacobian matrix already computed. if ( present ( fjac )) then ! dense do i = 1 , me % n gradf ( i ) = dot_product ( fvec , fjac (:, i )) end do else ! sparse do i = 1 , me % n gradf ( i ) = dot_product ( fvec , pack ( fjac_sparse , mask = me % icol == i )) end do end if slope = dot_product ( p , gradf ) t = - me % c * slope if ( me % verbose ) then write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        slope    = ' , slope write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        t        = ' , t end if ! perform the line search: min_alpha_reached = . false . alpha = me % alpha_max ! start with the largest step do xtmp = xold + p * alpha call me % func ( xtmp , fvectmp ) ftmp = norm2 ( fvectmp ) if ( me % verbose ) then write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        alpha    = ' , alpha , ' f       = ' , ftmp if ( f - ftmp >= alpha * t ) then write ( me % iunit , '(1P,2(A,1X,E16.6),1X,A)' ) '        f - ftmp = ' , f - ftmp , ' alpha*t = ' , alpha * t , ' [ACCEPTED]' else write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        f - ftmp = ' , f - ftmp , ' alpha*t = ' , alpha * t end if end if if ((( f - ftmp ) / 2.0_wp >= alpha * t ) . or . min_alpha_reached ) then if ( min_alpha_reached ) then write ( me % iunit , '(A)' ) '        Minimum alpha reached' end if ! Armijo-Goldstein condition is satisfied ! (or the min step has been reached) x = xtmp fvec = fvectmp f = ftmp exit end if alpha = alpha * me % tau ! reduce step size if ( alpha <= me % alpha_min ) then alpha = me % alpha_min min_alpha_reached = . true . ! will stop on the next step end if end do end subroutine backtracking_linesearch","tags":"","loc":"proc/backtracking_linesearch.html"},{"title":"exact_linesearch – nlesolver-fortran","text":"private  subroutine exact_linesearch(me, xold, p, x, f, fvec, fjac, fjac_sparse) An exact linesearch that uses a derivative-free minimizer to\nfind the minimum value of f(x) between x = xold + p * alpha_min and x = xold + p * alpha_max . Usually this is overkill and not necessary, but is here as an option for testing. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] Calls proc~~exact_linesearch~~CallsGraph proc~exact_linesearch nlesolver_module::exact_linesearch fmin fmin proc~exact_linesearch->fmin Help Graph Key Nodes of different colours represent the following: Graph Key Subroutine Subroutine Function Function Interface Interface Type Bound Procedure Type Bound Procedure Unknown Procedure Type Unknown Procedure Type Program Program This Page's Entity This Page's Entity Solid arrows point from a procedure to one which it calls. Dashed \narrows point from an interface to procedures which implement that interface.\nThis could include the module procedures in a generic interface or the\nimplementation in a submodule of an interface in a parent module. Source Code subroutine exact_linesearch ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] real ( wp ), dimension (:), allocatable :: xnew !! used in [[func_for_fmin]] real ( wp ) :: alpha_min allocate ( xnew ( me % n )) ! find the minimum value of f in the range of alphas: alpha_min = fmin ( func_for_fmin , me % alpha_min , me % alpha_max , me % fmin_tol ) if ( me % verbose ) write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        alpha_min = ' , alpha_min x = xold + p * alpha_min if ( all ( x == xnew )) then ! already computed in the func else call me % func ( x , fvec ) f = norm2 ( fvec ) end if contains real ( wp ) function func_for_fmin ( alpha ) !! function for [[fmin]] implicit none real ( wp ), intent ( in ) :: alpha !! indep variable xnew = xold + p * alpha call me % func ( xnew , fvec ) func_for_fmin = norm2 ( fvec ) ! return result f = func_for_fmin ! just in case this is the solution end function func_for_fmin end subroutine exact_linesearch","tags":"","loc":"proc/exact_linesearch.html"},{"title":"fixed_point_linesearch – nlesolver-fortran","text":"private  subroutine fixed_point_linesearch(me, xold, p, x, f, fvec, fjac, fjac_sparse) A simple search that just evaluates the function at a specified\nnumber of points and picks the one with the minimum function value. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] Source Code subroutine fixed_point_linesearch ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] integer :: i !! counter integer :: n_points !! number of points to compute real ( wp ), dimension (:), allocatable :: alphas_to_try !! set of `alpha` values to try real ( wp ), dimension (:), allocatable :: x_tmp !! temp `x` real ( wp ), dimension (:), allocatable :: fvec_tmp !! temp `fvec` real ( wp ) :: f_tmp !! temp `f` real ( wp ) :: step_size !! step size for `alpha` integer :: n !! number of steps to divide the interval ! 1 o-----------o ! 2 o-----o-----o ! 3 o---o---o---o n = me % n_intervals n_points = n + 1 allocate ( alphas_to_try ( n_points )) allocate ( x_tmp ( me % n )) allocate ( fvec_tmp ( me % m )) step_size = ( me % alpha_max - me % alpha_min ) / real ( n , wp ) ! compute the alphas: alphas_to_try ( 1 ) = me % alpha_min do i = 2 , n alphas_to_try ( i ) = alphas_to_try ( i - 1 ) + step_size end do alphas_to_try ( n_points ) = me % alpha_max ! now compute the functions at these alphas: f = big do i = 1 , n_points x_tmp = xold + p * alphas_to_try ( i ) ! evaluate the function at tthis point: call me % func ( x_tmp , fvec_tmp ) f_tmp = norm2 ( fvec_tmp ) if ( f_tmp <= f ) then ! new best point x = x_tmp f = f_tmp fvec = fvec_tmp end if end do end subroutine fixed_point_linesearch","tags":"","loc":"proc/fixed_point_linesearch.html"},{"title":"nlesolver_module – nlesolver-fortran","text":"A basic multidimensional nonlinear equation solver, using a Newton-Raphson type direct method. Features Works with square, under-determined, or over-determined systems. Uses LAPACK routines ( dgesv or dgels ) to solve the linear system. Has a Broyden update option. Has various line search options. References https://en.wikipedia.org/wiki/Backtracking_line_search http://projecteuclid.org/download/pdf_1/euclid.pjm/1102995080 http://help.agi.com/stk/index.htm#gator/eq-diffcorr.htm http://gmat.sourceforge.net/doc/R2015a/html/DifferentialCorrector.html Author Jacob Williams License BSD-3 Todo add an istat output to func and grad, for user stopping\n      or to take a smaller stop (if istat>0 take a smaller step, if istat<0 abort) Note The default real kind ( wp ) can be\n      changed using optional preprocessor flags.\n      This library was built with real kind: real(kind=real64) [8 bytes] Uses lusol_ez_module lsqr_module iso_fortran_env fmin_module module~~nlesolver_module~~UsesGraph module~nlesolver_module nlesolver_module fmin_module fmin_module module~nlesolver_module->fmin_module iso_fortran_env iso_fortran_env module~nlesolver_module->iso_fortran_env lsqr_module lsqr_module module~nlesolver_module->lsqr_module lusol_ez_module lusol_ez_module module~nlesolver_module->lusol_ez_module Help Graph Key Nodes of different colours represent the following: Graph Key Module Module Submodule Submodule Subroutine Subroutine Function Function Program Program This Page's Entity This Page's Entity Solid arrows point from a submodule to the (sub)module which it is\ndescended from. Dashed arrows point from a module or program unit to \nmodules which it uses. Variables Type Visibility Attributes Name Initial integer, public, parameter :: nlesolver_rk = real64 real kind used by this module [8 bytes] integer, private, parameter :: wp = nlesolver_rk local copy of nlesolver_rk with a shorter name real(kind=wp), private, parameter :: zero = 0.0_wp real(kind=wp), private, parameter :: one = 1.0_wp real(kind=wp), private, parameter :: two = 2.0_wp real(kind=wp), private, parameter :: eps = epsilon(one) machine real(kind=wp), private, parameter :: big = huge(one) Abstract Interfaces abstract interface private  subroutine func_func(me, x, f) compute the function Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(out), dimension(:) :: f abstract interface private  subroutine grad_func(me, x, g) compute the gradient of the function (Jacobian). Dense version. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(out), dimension(:,:) :: g abstract interface private  subroutine grad_func_sparse(me, x, g) compute the gradient of the function (Jacobian). Sparse version. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(out), dimension(:) :: g sparse jacobian. length is n_nonzeros abstract interface private  subroutine export_func(me, x, f, iter) export an iteration: Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(in), dimension(:) :: f integer, intent(in) :: iter iteration number abstract interface private  subroutine wait_func(me, user_stop) enable a user-triggered stop of the iterations: Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me logical, intent(out) :: user_stop abstract interface private  subroutine linesearch_func(me, xold, p, x, f, fvec, fjac, fjac_sparse) line search method. Note that not all inputs/outputs are\nused by all methods. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f input: current magnitude of fvec , output: new value of f real(kind=wp), intent(inout), dimension(me%m) :: fvec input: current function vector, output: new function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] Derived Types type, public :: nlesolver_type Nonlinear equations solver class. Components Type Visibility Attributes Name Initial integer, private :: n = 0 number of opt vars integer, private :: m = 0 number of constraints integer, private :: max_iter = 100 maximum number of iterations real(kind=wp), private :: tol = 1.0e-6_wp convergence tolerance for function values real(kind=wp), private :: alpha = 1.0_wp step length (when specified constant) real(kind=wp), private :: alpha_min = 0.1_wp minimum step length (when allowed to vary) real(kind=wp), private :: alpha_max = 1.0_wp maximum step length (when allowed to vary) real(kind=wp), private :: tolx = 1.0e-8_wp convergence tolerance for x real(kind=wp), private :: c = 0.5_wp backtracking linesearch parameter (0,1) real(kind=wp), private :: tau = 0.5_wp backtracking linesearch parameter (0,1) real(kind=wp), private :: fmin_tol = 1.0e-5_wp tolerance for \"exact\" linesearch integer, private :: n_intervals = 2 number of intervals for fixed point linesearch logical, private :: use_broyden = .false. if true, a Broyden update is used\nrather than computing the Jacobian\nat every step. The grad function is\nonly called for the initial evaluation. integer, private :: broyden_update_n = 4 if this value is >0 , the Broyden update\nis computed at most this many times before\nthe full Jacobian is recomputed. integer, private :: n_uphill_max = 5 maximum number of consecutive steps\nto allow where the value of f increases logical, private :: verbose = .false. verbose output printing integer, private :: iunit = output_unit output unit for printing (assumed to be open). character(len=:), private, allocatable :: message latest status message integer, private :: istat = -999 latest status message procedure( func_func ), private, pointer :: func => null() user-supplied routine to compute the function procedure( export_func ), private, pointer :: export_iteration => null() user-supplied routine to export iterations procedure( wait_func ), private, pointer :: user_input_check => null() user-supplied routine to enable user to stop iterations procedure( linesearch_func ), private, pointer :: linesearch => null() line search method (determined by step_mode user input in initialize ) integer, private :: sparsity_mode = 1 sparsity mode: Read more… integer, private :: n_nonzeros = -1 number of nonzero Jacobian elements (used for sparsity_mode > 1 ) integer, private, dimension(:), allocatable :: irow sparsity pattern nonzero elements row indices. integer, private, dimension(:), allocatable :: icol sparsity pattern nonzero elements column indices real(kind=wp), private :: atol = zero relative error in definition of A real(kind=wp), private :: btol = zero relative error in definition of b real(kind=wp), private :: conlim = zero An upper limit on cond(Abar) , the apparent\ncondition number of the matrix Abar . integer, private :: itnlim = 100 max iterations integer, private :: nout = 0 output unit for printing real(kind=wp), private :: damp = zero damp parameter for LSQR integer, private :: lusol_method = 0 procedure( grad_func ), private, pointer :: grad => null() user-supplied routine to compute the gradient of the function (dense version) procedure( grad_func_sparse ), private, pointer :: grad_sparse => null() user-supplied routine to compute the gradient of the function (sparse version) Type-Bound Procedures procedure, public :: initialize => initialize_nlesolver_variables procedure, public :: solve => nlesolver_solver procedure, public :: destroy => destroy_nlesolver_variables procedure, public :: status => get_status procedure, private :: set_status Subroutines private  subroutine set_status (me, istat, string, i, r) Set status flag and message. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(in) :: istat status code character(len=*), intent(in) :: string status message integer, intent(in), optional :: i an integer value to append real(kind=wp), intent(in), optional :: r a real value to append private  subroutine get_status (me, istat, message) Return the status code and message from the nlesolver_type class. Read more… Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(out), optional :: istat Integer status code. character(len=:), intent(out), optional, allocatable :: message Text status message private  subroutine initialize_nlesolver_variables (me, n, m, max_iter, tol, alpha, alpha_min, alpha_max, tolx, fmin_tol, backtrack_c, backtrack_tau, use_broyden, broyden_update_n, step_mode, func, grad, grad_sparse, export_iteration, user_input_check, verbose, iunit, n_uphill_max, n_intervals, sparsity_mode, irow, icol, atol, btol, conlim, damp, itnlim, nout, lusol_method) Constructor for the class. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(in) :: n number of optimization variables integer, intent(in) :: m number of constraints integer, intent(in) :: max_iter maximum number of iterations real(kind=wp), intent(in) :: tol function convergence tolerance real(kind=wp), intent(in), optional :: alpha constant step length for step_mode=1 (0,1] real(kind=wp), intent(in), optional :: alpha_min minimum step length (0,1] real(kind=wp), intent(in), optional :: alpha_max maximum step length (0,1] real(kind=wp), intent(in), optional :: tolx convergence tolerance for changes in x real(kind=wp), intent(in), optional :: fmin_tol convergence tolerance for fmin (used when step_mode=3 ) real(kind=wp), intent(in), optional :: backtrack_c backtracking linesearch parameter (0,1) real(kind=wp), intent(in), optional :: backtrack_tau backtracking linesearch parameter (0,1) logical, intent(in), optional :: use_broyden use a Broyden update (default is False) integer, intent(in), optional :: broyden_update_n For Broyden mode, update the full Jacobian\nat most every this many iterations (must be >1)\nIf <=1 then Jacobian is only computed on the\nfirst iteration. integer, intent(in), optional :: step_mode step mode: Read more… procedure( func_func ) :: func computes the function vector procedure( grad_func ), optional :: grad computes the jacobian [required for dense mode: sparsity_mode=1 ] procedure( grad_func_sparse ), optional :: grad_sparse computes the jacobian [required for sparse mode: sparsity_mode>1 ] procedure( export_func ), optional :: export_iteration function to export each iteration procedure( wait_func ), optional :: user_input_check check for user input (to stop solver if necessary) logical, intent(in), optional :: verbose for verbose status printing integer, intent(in), optional :: iunit unit for verbose printing (assumed to be open).\nby default this is output_unit . integer, intent(in), optional :: n_uphill_max maximum number of consecutive steps\nto allow where the value of f increases integer, intent(in), optional :: n_intervals number of intervals for fixed point linesearch integer, intent(in), optional :: sparsity_mode sparsity mode: Read more… integer, intent(in), optional, dimension(:) :: irow sparsity pattern nonzero elements row indices.\nmust be specified with icol and be the same length ( n_nonzeros ). integer, intent(in), optional, dimension(:) :: icol sparsity pattern nonzero elements column indices\nmust be specified with icol and be the same length ( n_nonzeros ). real(kind=wp), intent(in), optional :: atol LSQR : relative error in definition of A real(kind=wp), intent(in), optional :: btol LSQR : relative error in definition of b real(kind=wp), intent(in), optional :: conlim LSQR : An upper limit on cond(Abar) , the apparent\ncondition number of the matrix Abar . real(kind=wp), intent(in), optional :: damp LSQR : damp factor integer, intent(in), optional :: itnlim LSQR : max iterations integer, intent(in), optional :: nout LSQR : output unit for printing integer, intent(in), optional :: lusol_method private  subroutine nlesolver_solver (me, x) Main solver. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(inout), dimension(:) :: x private  subroutine destroy_nlesolver_variables (me) Destructor Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(out) :: me private  subroutine linear_solver (m, n, a, b, x, info) Solve the linear system: , using a dense, direct method. Read more… Arguments Type Intent Optional Attributes Name integer, intent(in) :: m number of rows in a integer, intent(in) :: n number of columns in a real(kind=wp), intent(in), dimension(m,n) :: a A matrix of the linear system real(kind=wp), intent(in), dimension(m) :: b RHS of the linear system real(kind=wp), intent(out), dimension(n) :: x the solution of the linear system. integer, intent(out) :: info output status flag ( =0 if success) private  subroutine simple_step (me, xold, p, x, f, fvec, fjac, fjac_sparse) Take a simple step in the search direction of p * alpha . Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] private  subroutine backtracking_linesearch (me, xold, p, x, f, fvec, fjac, fjac_sparse) Backtracking line search. Read more… Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] private  subroutine exact_linesearch (me, xold, p, x, f, fvec, fjac, fjac_sparse) An exact linesearch that uses a derivative-free minimizer to\nfind the minimum value of f(x) between x = xold + p * alpha_min and x = xold + p * alpha_max . Read more… Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] private  subroutine fixed_point_linesearch (me, xold, p, x, f, fvec, fjac, fjac_sparse) A simple search that just evaluates the function at a specified\nnumber of points and picks the one with the minimum function value. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse]","tags":"","loc":"module/nlesolver_module.html"},{"title":"nlesolver_module.F90 – nlesolver-fortran","text":"Source Code !****************************************************************************************************** !> !  A basic multidimensional nonlinear equation solver, using a Newton-Raphson type direct method. ! !### Features !  * Works with square, under-determined, or over-determined systems. !  * Uses LAPACK routines (`dgesv` or `dgels`) to solve the linear system. !  * Has a Broyden update option. !  * Has various line search options. ! !### References !  * https://en.wikipedia.org/wiki/Backtracking_line_search !  * http://projecteuclid.org/download/pdf_1/euclid.pjm/1102995080 !  * http://help.agi.com/stk/index.htm#gator/eq-diffcorr.htm !  * http://gmat.sourceforge.net/doc/R2015a/html/DifferentialCorrector.html ! !### Author !  * Jacob Williams ! !### License !  * BSD-3 ! !@todo add an `istat` output to func and grad, for user stopping !      or to take a smaller stop (if istat>0 take a smaller step, if istat<0 abort) ! !@note The default real kind (`wp`) can be !      changed using optional preprocessor flags. !      This library was built with real kind: #ifdef REAL32 !      `real(kind=real32)` [4 bytes] #elif REAL64 !      `real(kind=real64)` [8 bytes] #elif REAL128 !      `real(kind=real128)` [16 bytes] #else !      `real(kind=real64)` [8 bytes] #endif module nlesolver_module use iso_fortran_env use fmin_module , only : fmin use lsqr_module , only : lsqr_solver_ez use lusol_ez_module , only : solve , lusol_settings implicit none private #ifdef REAL32 integer , parameter , public :: nlesolver_rk = real32 !! real kind used by this module [4 bytes] #elif REAL64 integer , parameter , public :: nlesolver_rk = real64 !! real kind used by this module [8 bytes] #elif REAL128 integer , parameter , public :: nlesolver_rk = real128 !! real kind used by this module [16 bytes] #else integer , parameter , public :: nlesolver_rk = real64 !! real kind used by this module [8 bytes] #endif integer , parameter :: wp = nlesolver_rk !! local copy of `nlesolver_rk` with a shorter name real ( wp ), parameter :: zero = 0.0_wp real ( wp ), parameter :: one = 1.0_wp real ( wp ), parameter :: two = 2.0_wp real ( wp ), parameter :: eps = epsilon ( one ) !! machine  \\epsilon  real ( wp ), parameter :: big = huge ( one ) !********************************************************* type , public :: nlesolver_type !! Nonlinear equations solver class. private integer :: n = 0 !! number of opt vars integer :: m = 0 !! number of constraints integer :: max_iter = 100 !! maximum number of iterations real ( wp ) :: tol = 1.0e-6_wp !! convergence tolerance for function values real ( wp ) :: alpha = 1.0_wp !! step length (when specified constant) real ( wp ) :: alpha_min = 0.1_wp !! minimum step length (when allowed to vary) real ( wp ) :: alpha_max = 1.0_wp !! maximum step length (when allowed to vary) real ( wp ) :: tolx = 1.0e-8_wp !! convergence tolerance for `x` real ( wp ) :: c = 0.5_wp !! backtracking linesearch parameter (0,1) real ( wp ) :: tau = 0.5_wp !! backtracking linesearch parameter (0,1) real ( wp ) :: fmin_tol = 1.0e-5_wp !! tolerance for \"exact\" linesearch integer :: n_intervals = 2 !! number of intervals for fixed point linesearch logical :: use_broyden = . false . !! if true, a Broyden update is used !! rather than computing the Jacobian !! at every step. The `grad` function is !! only called for the initial evaluation. integer :: broyden_update_n = 4 !! if this value is `>0`, the Broyden update !! is computed at most this many times before !! the full Jacobian is recomputed. integer :: n_uphill_max = 5 !! maximum number of consecutive steps !! to allow where the value of `f` increases logical :: verbose = . false . !! verbose output printing integer :: iunit = output_unit !! output unit for printing (assumed to be open). character ( len = :), allocatable :: message !! latest status message integer :: istat = - 999 !! latest status message procedure ( func_func ), pointer :: func => null () !! user-supplied routine to compute the function procedure ( export_func ), pointer :: export_iteration => null () !! user-supplied routine to export iterations procedure ( wait_func ), pointer :: user_input_check => null () !! user-supplied routine to enable user to stop iterations procedure ( linesearch_func ), pointer :: linesearch => null () !! line search method (determined by `step_mode` user input in [[nlesolver_type:initialize]]) ! sparsity options: integer :: sparsity_mode = 1 !! sparsity mode: !! !! * 1 - assume dense (use dense solver) !! * 2 - assume sparse (use LSQR sparse solver). !! * 3 - assume sparse (use LUSOL sparse solver). integer :: n_nonzeros = - 1 !! number of nonzero Jacobian elements (used for `sparsity_mode > 1`) integer , dimension (:), allocatable :: irow !! sparsity pattern nonzero elements row indices. integer , dimension (:), allocatable :: icol !! sparsity pattern nonzero elements column indices ! LSQR parameters: real ( wp ) :: atol = zero !! relative error in definition of `A` real ( wp ) :: btol = zero !! relative error in definition of `b` real ( wp ) :: conlim = zero !! An upper limit on `cond(Abar)`, the apparent !! condition number of the matrix `Abar`. integer :: itnlim = 100 !! max iterations integer :: nout = 0 !! output unit for printing real ( wp ) :: damp = zero !! damp parameter for LSQR ! LUSOL parameters: integer :: lusol_method = 0 ! dense version: procedure ( grad_func ), pointer :: grad => null () !! user-supplied routine to compute the gradient of the function (dense version) ! sparse version: procedure ( grad_func_sparse ), pointer :: grad_sparse => null () !! user-supplied routine to compute the gradient of the function (sparse version) contains private procedure , public :: initialize => initialize_nlesolver_variables procedure , public :: solve => nlesolver_solver procedure , public :: destroy => destroy_nlesolver_variables procedure , public :: status => get_status procedure :: set_status end type nlesolver_type !********************************************************* abstract interface subroutine func_func ( me , x , f ) !! compute the function import :: wp , nlesolver_type implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension (:), intent ( in ) :: x real ( wp ), dimension (:), intent ( out ) :: f end subroutine func_func subroutine grad_func ( me , x , g ) !! compute the gradient of the function (Jacobian). Dense version. import :: wp , nlesolver_type implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension (:), intent ( in ) :: x real ( wp ), dimension (:,:), intent ( out ) :: g end subroutine grad_func subroutine grad_func_sparse ( me , x , g ) !! compute the gradient of the function (Jacobian). Sparse version. import :: wp , nlesolver_type implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension (:), intent ( in ) :: x real ( wp ), dimension (:), intent ( out ) :: g !! sparse jacobian. length is `n_nonzeros` end subroutine grad_func_sparse subroutine export_func ( me , x , f , iter ) !! export an iteration: import :: wp , nlesolver_type implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension (:), intent ( in ) :: x real ( wp ), dimension (:), intent ( in ) :: f integer , intent ( in ) :: iter !! iteration number end subroutine export_func subroutine wait_func ( me , user_stop ) !! enable a user-triggered stop of the iterations: import :: wp , nlesolver_type implicit none class ( nlesolver_type ), intent ( inout ) :: me logical , intent ( out ) :: user_stop end subroutine wait_func subroutine linesearch_func ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) !! line search method. Note that not all inputs/outputs are !! used by all methods. import :: wp , nlesolver_type implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! * input: current magnitude of `fvec`, !! * output: new value of `f` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! * input: current function vector, !! * output: new function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] end subroutine linesearch_func end interface contains !******************************************************************************************************* !***************************************************************************************** !> !  Set status flag and message. subroutine set_status ( me , istat , string , i , r ) implicit none class ( nlesolver_type ), intent ( inout ) :: me integer , intent ( in ) :: istat !! status code character ( len =* ), intent ( in ) :: string !! status message integer , intent ( in ), optional :: i !! an integer value to append real ( wp ), intent ( in ), optional :: r !! a real value to append character ( len = 256 ) :: numstr !! for number fo string conversion character ( len = :), allocatable :: message !! the full message to log integer :: iostat !! write `iostat` code message = trim ( string ) if ( present ( i )) then numstr = '' write ( numstr , fmt =* , iostat = iostat ) i if ( iostat /= 0 ) numstr = '****' message = message // ' ' // trim ( adjustl ( numstr )) end if if ( present ( r )) then numstr = '' write ( numstr , fmt =* , iostat = iostat ) r if ( iostat /= 0 ) numstr = '****' message = message // ' ' // trim ( adjustl ( numstr )) end if if ( me % verbose ) then write ( me % iunit , '(A)' , iostat = iostat ) message end if ! store in the class: me % istat = istat me % message = message end subroutine set_status !***************************************************************************************** !***************************************************************************************** !> !  Return the status code and message from the [[nlesolver_type]] class. ! !### Status codes ! !  * -1   -- Error: Invalid alpha !  * -2   -- Error: Invalid alpha_min !  * -3   -- Error: Invalid alpha_max !  * -4   -- Error: Alpha_min must be < alpha_max !  * -5   -- Error: Invalid step_mode !  * -6   -- Error solving linear system !  * -7   -- Error: More than 5 steps in the uphill direction !  * -8   -- Error: Divide by zero when computing Broyden update !  * -9   -- Error: Out of memory !  * -10  -- Error: function routine is not associated !  * -11  -- Error: gradient routine is not associated !  * -12  -- Error: backtracking linesearch c must be in range (0, 1) !  * -13  -- Error: backtracking linesearch tau must be in range (0, 1) !  * -14  -- Error: must specify grad_sparse, irow, and icol for sparsity_mode > 1 !  * -15  -- Error: irow and icol must be the same length !  * -999 -- Error: class has not been initialized !  * 0    -- Class successfully initialized in [[nlesolver_type:initialize]] !  * 1    -- Required accuracy achieved !  * 2    -- Solution cannot be improved !  * 3    -- Maximum number of iterations reached !  * 4    -- Stopped by the user subroutine get_status ( me , istat , message ) implicit none class ( nlesolver_type ), intent ( inout ) :: me integer , intent ( out ), optional :: istat !! Integer status code. character ( len = :), allocatable , intent ( out ), optional :: message !! Text status message if ( present ( istat )) istat = me % istat if ( present ( message )) then if ( allocated ( me % message )) then message = trim ( me % message ) else message = 'Error: class has not been initialized' end if end if end subroutine get_status !***************************************************************************************** !***************************************************************************************** !> !  Constructor for the class. subroutine initialize_nlesolver_variables ( me ,& n , m , max_iter , tol , alpha , alpha_min , alpha_max , tolx , fmin_tol ,& backtrack_c , backtrack_tau ,& use_broyden , broyden_update_n , step_mode ,& func , grad , grad_sparse ,& export_iteration , user_input_check ,& verbose , iunit , n_uphill_max , n_intervals ,& sparsity_mode , irow , icol ,& atol , btol , conlim , damp , itnlim , nout ,& lusol_method ) implicit none class ( nlesolver_type ), intent ( inout ) :: me integer , intent ( in ) :: n !! number of optimization variables integer , intent ( in ) :: m !! number of constraints integer , intent ( in ) :: max_iter !! maximum number of iterations real ( wp ), intent ( in ) :: tol !! function convergence tolerance procedure ( func_func ) :: func !! computes the function vector procedure ( grad_func ), optional :: grad !! computes the jacobian [required for dense mode: `sparsity_mode=1`] procedure ( grad_func_sparse ), optional :: grad_sparse !! computes the jacobian [required for sparse mode: `sparsity_mode>1`] integer , intent ( in ), optional :: step_mode !! step mode: !! !!  * 1 = use the specified `alpha` (0,1] !!  * 2 = backtracking linesearch (between `alpha_min` and `alpha_max`) !!  * 3 = exact linesearch (between `alpha_min` and `alpha_max`) !!  * 4 = evaluate function at specified fixed points  (between `alpha_min` and `alpha_max`) real ( wp ), intent ( in ), optional :: alpha !! constant step length for `step_mode=1` (0,1] real ( wp ), intent ( in ), optional :: alpha_min !! minimum step length (0,1] real ( wp ), intent ( in ), optional :: alpha_max !! maximum step length (0,1] real ( wp ), intent ( in ), optional :: tolx !! convergence tolerance for changes in `x` real ( wp ), intent ( in ), optional :: fmin_tol !! convergence tolerance for [[fmin]] (used when `step_mode=3`) real ( wp ), intent ( in ), optional :: backtrack_c !! backtracking linesearch parameter (0,1) real ( wp ), intent ( in ), optional :: backtrack_tau !! backtracking linesearch parameter (0,1) logical , intent ( in ), optional :: use_broyden !! use a Broyden update (default is False) integer , intent ( in ), optional :: broyden_update_n !! For Broyden mode, update the full Jacobian !! at most every this many iterations (must be >1) !! If <=1 then Jacobian is only computed on the !! first iteration. procedure ( export_func ), optional :: export_iteration !! function to export each iteration procedure ( wait_func ), optional :: user_input_check !! check for user input (to stop solver if necessary) logical , intent ( in ), optional :: verbose !! for verbose status printing integer , intent ( in ), optional :: iunit !! unit for verbose printing (assumed to be open). !! by default this is `output_unit`. integer , intent ( in ), optional :: n_uphill_max !! maximum number of consecutive steps !! to allow where the value of `f` increases integer , intent ( in ), optional :: n_intervals !! number of intervals for fixed point linesearch integer , intent ( in ), optional :: sparsity_mode !! sparsity mode: !! !! * 1 - assume dense (use dense solver) !!   Must specify `grad` for this mode. !! * 2 - assume sparse (use LSQR sparse solver). !! * 3 - assume sparse (use LUSOL sparse solver). !! Must also specify `grad_sparse` and the `irow` and `icol` !! sparsity pattern for `mode>1`. integer , dimension (:), intent ( in ), optional :: irow !! sparsity pattern nonzero elements row indices. !! must be specified with `icol` and be the same length (`n_nonzeros`). integer , dimension (:), intent ( in ), optional :: icol !! sparsity pattern nonzero elements column indices !! must be specified with `icol` and be the same length (`n_nonzeros`). real ( wp ), intent ( in ), optional :: atol !! `LSQR`: relative error in definition of `A` real ( wp ), intent ( in ), optional :: btol !! `LSQR`: relative error in definition of `b` real ( wp ), intent ( in ), optional :: conlim !! `LSQR`: An upper limit on `cond(Abar)`, the apparent !! condition number of the matrix `Abar`. real ( wp ), intent ( in ), optional :: damp !! `LSQR`: damp factor integer , intent ( in ), optional :: itnlim !! `LSQR`: max iterations integer , intent ( in ), optional :: nout !! `LSQR`: output unit for printing integer , intent ( in ), optional :: lusol_method logical :: status_ok !! true if there were no errors status_ok = . true . !required: me % n = abs ( n ) me % m = abs ( m ) me % max_iter = abs ( max_iter ) me % tol = abs ( tol ) me % func => func if ( present ( grad )) me % grad => grad if ( present ( grad_sparse )) me % grad_sparse => grad_sparse !optional: if ( present ( step_mode )) then select case ( step_mode ) case ( 1 ) ! = use the specified `alpha` (0,1] me % linesearch => simple_step case ( 2 ) ! = backtracking linesearch (between `alpha_min` and `alpha_max`) me % linesearch => backtracking_linesearch case ( 3 ) ! = exact linesearch (between `alpha_min` and `alpha_max`) me % linesearch => exact_linesearch case ( 4 ) ! = evaluate function at specified fixed points (between `alpha_min` and `alpha_max`) me % linesearch => fixed_point_linesearch case default status_ok = . false . call me % set_status ( istat = - 5 , string = 'Error: invalid step_mode:' , i = step_mode ) return end select else me % linesearch => simple_step end if if ( present ( alpha )) me % alpha = abs ( alpha ) if ( present ( alpha_min )) me % alpha_min = abs ( alpha_min ) if ( present ( alpha_max )) me % alpha_max = abs ( alpha_max ) if ( present ( tolx )) me % tolx = abs ( tolx ) if ( present ( backtrack_c )) me % c = abs ( backtrack_c ) if ( present ( backtrack_tau )) me % tau = abs ( backtrack_tau ) if ( present ( use_broyden )) me % use_broyden = use_broyden if ( present ( broyden_update_n )) me % broyden_update_n = abs ( broyden_update_n ) if ( present ( verbose )) me % verbose = verbose if ( present ( iunit )) me % iunit = iunit if ( present ( n_uphill_max )) me % n_uphill_max = abs ( n_uphill_max ) if ( present ( n_intervals )) me % n_intervals = max ( abs ( n_intervals ), 1 ) if ( present ( fmin_tol )) me % fmin_tol = abs ( fmin_tol ) if ( present ( export_iteration )) me % export_iteration => export_iteration if ( present ( user_input_check )) me % user_input_check => user_input_check ! error checks: if ( me % alpha < zero . or . me % alpha > one ) then status_ok = . false . call me % set_status ( istat = - 1 , string = 'Error: invalid alpha:' , r = me % alpha ) return end if if ( me % alpha_min < zero . or . me % alpha_min > one ) then status_ok = . false . call me % set_status ( istat = - 2 , string = 'Error: invalid alpha_min:' , r = me % alpha_min ) return end if if ( me % alpha_max < zero . or . me % alpha_max > one ) then status_ok = . false . call me % set_status ( istat = - 3 , string = 'Error: invalid alpha_max:' , r = me % alpha_max ) return end if if ( me % alpha_max <= me % alpha_min ) then status_ok = . false . call me % set_status ( istat = - 4 , string = 'Error: alpha_min must be < alpha_max' ) return end if if ( me % c < zero . or . me % c > one ) then status_ok = . false . call me % set_status ( istat = - 12 , string = 'Error: backtracking linesearch c must be in range (0, 1):' , r = me % c ) return end if if ( me % tau < zero . or . me % tau > one ) then status_ok = . false . call me % set_status ( istat = - 13 , string = 'Error: backtracking linesearch tau must be in range (0, 1):' , r = me % tau ) return end if ! initialize: me % n_nonzeros = - 1 ! not used if ( allocated ( me % irow )) deallocate ( me % irow ) if ( allocated ( me % icol )) deallocate ( me % icol ) if ( present ( sparsity_mode )) then me % sparsity_mode = sparsity_mode if ( sparsity_mode > 1 ) then ! sparse solver method if ( present ( irow ) . and . present ( icol ) . and . present ( grad_sparse )) then if ( size ( irow ) == size ( icol )) then me % n_nonzeros = size ( irow ) me % irow = irow me % icol = icol else call me % set_status ( istat = - 15 , string = 'Error: irow and icol must be the same length' ) return end if else call me % set_status ( istat = - 14 , string = 'Error: must specify grad_sparse, irow, and icol for sparsity_mode > 1' ) return end if ! LSQR optional inputs: if ( present ( atol )) me % atol = atol if ( present ( btol )) me % btol = btol if ( present ( conlim )) me % conlim = conlim if ( present ( damp )) me % damp = damp if ( present ( itnlim )) me % itnlim = itnlim if ( present ( nout )) me % nout = nout ! LUSOL method if ( present ( nout )) me % lusol_method = lusol_method ! now now, some options are not available for sparse mode !...see if this is possible in sparse mode... TODO if ( me % use_broyden ) then call me % set_status ( istat = - 16 , string = 'Error: broyden method not available for sparse solver' ) return end if end if end if if ( status_ok ) then call me % set_status ( istat = 0 , string = 'Class successfully initialized' ) end if end subroutine initialize_nlesolver_variables !***************************************************************************************** !***************************************************************************************** !> !  Main solver. subroutine nlesolver_solver ( me , x ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension (:), intent ( inout ) :: x real ( wp ), dimension (:) , allocatable :: fvec !! function vector real ( wp ), dimension (:,:), allocatable :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), allocatable :: fjac_sparse !! jacobian matrix [sparse] real ( wp ), dimension (:) , allocatable :: rhs !! linear system right-hand side real ( wp ), dimension (:) , allocatable :: p !! search direction real ( wp ), dimension (:) , allocatable :: xold !! previous value of `x` real ( wp ), dimension (:) , allocatable :: prev_fvec !! previous function vector real ( wp ), dimension (:,:), allocatable :: prev_fjac !! previous jacobian matrix real ( wp ), dimension (:,:), allocatable :: delf !! used for Broyden (rank 2 for `matmul`) real ( wp ), dimension (:,:), allocatable :: delx !! used for Broyden (rank 2 for `matmul`) logical :: user_stop !! user stop button flag integer :: info !! status flag from the [[linear_solver]] integer :: iter !! iteration counter real ( wp ) :: f !! magnitude of `fvec` real ( wp ) :: fold !! previous value of `f` integer :: n_uphill !! number of steps taken in the \"uphill\" direction !! (where `f` is increasing) real ( wp ) :: delxmag2 !! used for Broyden logical :: recompute_jac !! if using Broyden, and we want to call the user !! jacobian routine instead integer :: broyden_counter !! number of times the broyden update has been used integer :: alloc_stat !! allocation status flag type ( lsqr_solver_ez ) :: sparse_solver !! sparse LSQR solver class type ( lusol_settings ) :: lusol_options if ( me % istat < 0 ) return ! class was not initialized properly if (. not . associated ( me % func )) then call me % set_status ( istat = - 10 , string = 'Error: function routine is not associated' ) return end if if ( me % sparsity_mode == 1 . and . . not . associated ( me % grad )) then call me % set_status ( istat = - 11 , string = 'Error: gradient routine is not associated' ) return end if if ( me % sparsity_mode > 1 . and . . not . associated ( me % grad_sparse )) then call me % set_status ( istat = - 11 , string = 'Error: gradient routine is not associated' ) return end if ! initialize: iter = 0 n_uphill = 0 recompute_jac = . false . broyden_counter = 0 ! allocate the arrays: alloc_stat = 0 if ( alloc_stat == 0 ) allocate ( fvec ( me % m ) , stat = alloc_stat ) if ( me % sparsity_mode == 1 ) then ! dense if ( alloc_stat == 0 ) allocate ( fjac ( me % m , me % n ) , stat = alloc_stat ) else ! sparse if ( alloc_stat == 0 ) allocate ( fjac_sparse ( me % n_nonzeros ) , stat = alloc_stat ) end if if ( alloc_stat == 0 ) allocate ( rhs ( me % m ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( p ( me % n ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( xold ( me % n ) , stat = alloc_stat ) if ( me % use_broyden ) then ! only need these for broyden: if ( alloc_stat == 0 ) allocate ( prev_fvec ( me % m ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( prev_fjac ( me % m , me % n ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( delf ( me % m , 1 ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( delx ( me % n , 1 ) , stat = alloc_stat ) end if if ( alloc_stat /= 0 ) then call me % set_status ( istat = - 9 , string = 'Error: Out of memory' ) return else me % istat = - 998 me % message = 'Unknown error' end if ! evaluate the function: call me % func ( x , fvec ) f = norm2 ( fvec ) ! check to see if initial guess is a root: if ( f <= me % tol ) then call me % set_status ( istat = 1 , string = 'Required accuracy achieved' ) else ! main iteration loop: do iter = 1 , me % max_iter ! Export the current iteration: if ( associated ( me % export_iteration )) call me % export_iteration ( x , fvec , iter ) ! Check for user stop: if ( associated ( me % user_input_check )) then call me % user_input_check ( user_stop ) if ( user_stop ) then call me % set_status ( istat = 4 , string = 'Stopped by the user' ) exit end if end if if ( me % use_broyden . and . . not . recompute_jac ) then if ( iter == 1 ) then ! always compute Jacobian on the first iteration call me % grad ( x , fjac ) broyden_counter = 0 else ! and use Broyden update to estimate Jacobian ! for subsequent iterations. ! note: fvec was computed the last iteration delx (:, 1 ) = x - xold delf (:, 1 ) = fvec - prev_fvec delxmag2 = dot_product ( delx (:, 1 ), delx (:, 1 )) if ( delxmag2 < eps ) then call me % set_status ( istat = - 8 , & string = 'Error: Divide by zero when computing Broyden update' ) exit end if ! Jacobian estimate: fjac = prev_fjac + & matmul (( delf - matmul ( prev_fjac , delx )),& transpose ( delx )) / delxmag2 broyden_counter = broyden_counter + 1 end if prev_fjac = fjac prev_fvec = fvec else ! compute the jacobian: select case ( me % sparsity_mode ) case ( 1 ) call me % grad ( x , fjac ) case ( 2 :) call me % grad_sparse ( x , fjac_sparse ) end select recompute_jac = . false . ! for broyden broyden_counter = 0 end if xold = x fold = f ! compute the search direction p by solving linear system: rhs = - fvec ! RHS of the linear system select case ( me % sparsity_mode ) case ( 1 ) ! use dense solver call linear_solver ( me % m , me % n , fjac , rhs , p , info ) case ( 2 ) ! initialize the LSQR sparse solver call sparse_solver % initialize ( me % m , me % n , fjac_sparse , me % irow , me % icol ,& atol = me % atol , & btol = me % btol , & conlim = me % conlim , & itnlim = me % itnlim , & nout = me % nout ) call sparse_solver % solve ( rhs , me % damp , p , info ) ! solve the linear system ! check convergence: select case ( info ) case ( 4 ) call me % set_status ( istat = - 1004 , & string = 'LSQR Error: The system appears to be ill-conditioned. istop =' , i = info ) exit case ( 5 ) call me % set_status ( istat = - 1005 , & string = 'LSQR Error: The iteration limit was reached. istop =' , i = info ) exit case default info = 0 end select case ( 3 ) ! use lusol solver lusol_options % method = me % lusol_method ! 0    =>  TPP: Threshold Partial   Pivoting. ! 1    =>  TRP: Threshold Rook      Pivoting. ! 2    =>  TCP: Threshold Complete  Pivoting. call solve ( me % n , me % m , me % n_nonzeros , me % irow , me % icol , fjac_sparse , rhs , p , info ,& settings = lusol_options ) end select ! check for errors: if ( info /= 0 ) then call me % set_status ( istat = - 6 , string = 'Error solving linear system. info =' , i = info ) exit else ! next step, using the specified method: call me % linesearch ( xold , p , x , f , fvec , fjac , fjac_sparse ) ! keep track of the number of steps in the \"uphill\" direction: if ( f > fold ) then n_uphill = n_uphill + 1 else n_uphill = 0 end if ! check for stopping conditions if ( f <= me % tol ) then call me % set_status ( istat = 1 , string = 'Required accuracy achieved' ) exit elseif ( maxval ( abs ( x - xold )) <= me % tolx ) then call me % set_status ( istat = 2 , string = 'Solution cannot be improved' ) exit elseif ( iter == me % max_iter ) then call me % set_status ( istat = 3 , string = 'Maximum number of iterations reached' ) exit elseif ( n_uphill > me % n_uphill_max ) then call me % set_status ( istat = 5 , string = 'Too many steps in the uphill direction' ) exit elseif ( me % use_broyden ) then ! If delxmag2 is too small when using broyden, just ! call the user-supplied jacobian function to avoid ! a divide by zero on the next step. This should ! normally only happen when the solution is almost converged. if ( norm2 ( x - xold ) ** 2 <= eps ) then recompute_jac = . true . else if ( me % broyden_update_n > 0 ) then ! Note that we also recompute if we have taken an uphill step if ( broyden_counter == me % broyden_update_n . or . n_uphill > 0 ) then ! time to recompute the full jacobian recompute_jac = . true . end if end if end if endif end if end do !end of iterations loop end if !Export the last iteration: iter = iter + 1 if ( associated ( me % export_iteration )) call me % export_iteration ( x , fvec , iter ) end subroutine nlesolver_solver !***************************************************************************************** !***************************************************************************************** !> !   Destructor subroutine destroy_nlesolver_variables ( me ) implicit none class ( nlesolver_type ), intent ( out ) :: me me % message = 'Error: class has not been initialized' me % istat = - 999 end subroutine destroy_nlesolver_variables !***************************************************************************************** !***************************************************************************************** !> !  Solve the linear system:  Ax = b , using a dense, direct method. ! !  * if `n=m` : use LAPACK `dgesv` (LU decomposition) !  * if `n/=m` : use LAPACK `dgels` (if m>n uses QR factorization, !    if m<n uses LQ factorization) subroutine linear_solver ( m , n , a , b , x , info ) implicit none integer , intent ( in ) :: n !! number of columns in `a` integer , intent ( in ) :: m !! number of rows in `a` real ( wp ), dimension ( m , n ), intent ( in ) :: a !! `A` matrix of the linear system real ( wp ), dimension ( m ), intent ( in ) :: b !! RHS of the linear system real ( wp ), dimension ( n ), intent ( out ) :: x !! the solution of the linear system. integer , intent ( out ) :: info !! output status flag (`=0` if success) ! LAPACK routine interfaces: interface subroutine dgesv ( n , nrhs , a , lda , ipiv , b , ldb , info ) !! See: [?gesv](https://www.intel.com/content/www/us/en/develop/documentation/onemkl-developer-reference-fortran/top/lapack-routines/lapack-linear-equation-routines/lapack-linear-equation-driver-routines/gesv.html) import :: wp implicit none integer :: info integer :: lda integer :: ldb integer :: n integer :: nrhs integer :: ipiv ( * ) real ( wp ) :: a ( lda , * ) real ( wp ) :: b ( ldb , * ) end subroutine dgesv subroutine dgels ( trans , m , n , nrhs , a , lda , b , ldb , work , lwork , info ) !! See: [?gels](https://www.intel.com/content/www/us/en/develop/documentation/onemkl-developer-reference-fortran/top/lapack-routines/lapack-least-squares-and-eigenvalue-problem/lapack-least-squares-eigenvalue-problem-driver/linear-least-squares-lls-problems-lapack-driver/gels.html) import :: wp implicit none character :: trans integer :: info integer :: lda integer :: ldb integer :: lwork integer :: m integer :: n integer :: nrhs real ( wp ) :: a ( lda , * ) real ( wp ) :: b ( ldb , * ) real ( wp ) :: work ( * ) end subroutine dgels end interface integer , dimension (:), allocatable :: ipiv !! pivot indices array real ( wp ), dimension (:,:), allocatable :: bmat !! copy of `b` so it won't be overwritten real ( wp ), dimension (:), allocatable :: work !! work array for `dgels` real ( wp ), dimension (:,:), allocatable :: amat !! copy of `a` so it won't be overwritten integer :: lwork !! size of `work` allocate ( amat ( m , n )) allocate ( bmat ( max ( 1 , m , n ), 1 )) if ( n == m ) then !normal inverse allocate ( ipiv ( n )) amat = a bmat ( 1 : n , 1 ) = b call dgesv ( n , 1 , amat , n , ipiv , bmat , n , info ) x = bmat ( 1 : n , 1 ) else amat = a bmat = zero bmat ( 1 : m , 1 ) = b lwork = min ( m , n ) + max ( 1 , m , n ) allocate ( work ( lwork )) call dgels ( 'N' , m , n , 1 , amat , m , bmat , max ( 1 , m , n ), work , lwork , info ) x = bmat ( 1 : n , 1 ) end if end subroutine linear_solver !***************************************************************************************** !***************************************************************************************** !> !  Take a simple step in the search direction of `p * alpha`. subroutine simple_step ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] x = xold + p * me % alpha !evaluate the function at the new point: call me % func ( x , fvec ) f = norm2 ( fvec ) end subroutine simple_step !***************************************************************************************** !***************************************************************************************** !> !  Backtracking line search. ! !### See also !  * [Backtracking line search](https://en.wikipedia.org/wiki/Backtracking_line_search) ! !@note Either `fjac` or `fjac_sparse` should be present. subroutine backtracking_linesearch ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] integer :: i !! counter real ( wp ) :: slope !! local slope of the function of `alpha` along the search direction used for line search logical :: min_alpha_reached !! if the minimum step size is reached during the line search real ( wp ) :: alpha !! `alpha` for the line search real ( wp ) :: ftmp !! `f` value for linesearch real ( wp ) :: t !! used for line search real ( wp ), dimension (:), allocatable :: gradf !! line search objective function gradient vector real ( wp ), dimension (:), allocatable :: xtmp !! `x` value for linesearch real ( wp ), dimension (:), allocatable :: fvectmp !! `fvec` value for linesearch ! allocate arrays: allocate ( gradf ( me % n )) allocate ( xtmp ( me % n )) allocate ( fvectmp ( me % m )) ! compute the gradient of the function to be minimized ! (which in this case is 1/2 the norm of fvec). Use the chain ! rule and the Jacobian matrix already computed. if ( present ( fjac )) then ! dense do i = 1 , me % n gradf ( i ) = dot_product ( fvec , fjac (:, i )) end do else ! sparse do i = 1 , me % n gradf ( i ) = dot_product ( fvec , pack ( fjac_sparse , mask = me % icol == i )) end do end if slope = dot_product ( p , gradf ) t = - me % c * slope if ( me % verbose ) then write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        slope    = ' , slope write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        t        = ' , t end if ! perform the line search: min_alpha_reached = . false . alpha = me % alpha_max ! start with the largest step do xtmp = xold + p * alpha call me % func ( xtmp , fvectmp ) ftmp = norm2 ( fvectmp ) if ( me % verbose ) then write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        alpha    = ' , alpha , ' f       = ' , ftmp if ( f - ftmp >= alpha * t ) then write ( me % iunit , '(1P,2(A,1X,E16.6),1X,A)' ) '        f - ftmp = ' , f - ftmp , ' alpha*t = ' , alpha * t , ' [ACCEPTED]' else write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        f - ftmp = ' , f - ftmp , ' alpha*t = ' , alpha * t end if end if if ((( f - ftmp ) / 2.0_wp >= alpha * t ) . or . min_alpha_reached ) then if ( min_alpha_reached ) then write ( me % iunit , '(A)' ) '        Minimum alpha reached' end if ! Armijo-Goldstein condition is satisfied ! (or the min step has been reached) x = xtmp fvec = fvectmp f = ftmp exit end if alpha = alpha * me % tau ! reduce step size if ( alpha <= me % alpha_min ) then alpha = me % alpha_min min_alpha_reached = . true . ! will stop on the next step end if end do end subroutine backtracking_linesearch !***************************************************************************************** !***************************************************************************************** !> !  An exact linesearch that uses a derivative-free minimizer to !  find the minimum value of `f(x)` between !  `x = xold + p * alpha_min` and !  `x = xold + p * alpha_max`. ! !  Usually this is overkill and not necessary, but is here as an option for testing. subroutine exact_linesearch ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] real ( wp ), dimension (:), allocatable :: xnew !! used in [[func_for_fmin]] real ( wp ) :: alpha_min allocate ( xnew ( me % n )) ! find the minimum value of f in the range of alphas: alpha_min = fmin ( func_for_fmin , me % alpha_min , me % alpha_max , me % fmin_tol ) if ( me % verbose ) write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        alpha_min = ' , alpha_min x = xold + p * alpha_min if ( all ( x == xnew )) then ! already computed in the func else call me % func ( x , fvec ) f = norm2 ( fvec ) end if contains real ( wp ) function func_for_fmin ( alpha ) !! function for [[fmin]] implicit none real ( wp ), intent ( in ) :: alpha !! indep variable xnew = xold + p * alpha call me % func ( xnew , fvec ) func_for_fmin = norm2 ( fvec ) ! return result f = func_for_fmin ! just in case this is the solution end function func_for_fmin end subroutine exact_linesearch !***************************************************************************************** !***************************************************************************************** !> !  A simple search that just evaluates the function at a specified !  number of points and picks the one with the minimum function value. subroutine fixed_point_linesearch ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] integer :: i !! counter integer :: n_points !! number of points to compute real ( wp ), dimension (:), allocatable :: alphas_to_try !! set of `alpha` values to try real ( wp ), dimension (:), allocatable :: x_tmp !! temp `x` real ( wp ), dimension (:), allocatable :: fvec_tmp !! temp `fvec` real ( wp ) :: f_tmp !! temp `f` real ( wp ) :: step_size !! step size for `alpha` integer :: n !! number of steps to divide the interval ! 1 o-----------o ! 2 o-----o-----o ! 3 o---o---o---o n = me % n_intervals n_points = n + 1 allocate ( alphas_to_try ( n_points )) allocate ( x_tmp ( me % n )) allocate ( fvec_tmp ( me % m )) step_size = ( me % alpha_max - me % alpha_min ) / real ( n , wp ) ! compute the alphas: alphas_to_try ( 1 ) = me % alpha_min do i = 2 , n alphas_to_try ( i ) = alphas_to_try ( i - 1 ) + step_size end do alphas_to_try ( n_points ) = me % alpha_max ! now compute the functions at these alphas: f = big do i = 1 , n_points x_tmp = xold + p * alphas_to_try ( i ) ! evaluate the function at tthis point: call me % func ( x_tmp , fvec_tmp ) f_tmp = norm2 ( fvec_tmp ) if ( f_tmp <= f ) then ! new best point x = x_tmp f = f_tmp fvec = fvec_tmp end if end do end subroutine fixed_point_linesearch !***************************************************************************************** !****************************************************************************************************** end module nlesolver_module !******************************************************************************************************","tags":"","loc":"sourcefile/nlesolver_module.f90.html"}]}
\ No newline at end of file
+var tipuesearch = {"pages":[{"title":" nlesolver-fortran ","text":"nlesolver-fortran Nonlinear Equation Solver with Modern Fortran. A basic Newton-Raphson type nonlinear equation solver for dense systems with m functions of n input variables. A work in progress. Status Features Is object-oriented. Works with square, under-determined, or over-determined systems. Three different methods to solve the linear system: LAPACK routines ( dgesv or dgels ) for dense systems: If n=m , uses dgesv (LU decomposition). If n/=m , uses dgels (if m>n uses QR factorization, if m<n uses LQ factorization). lsqr -- a conjugate-gradient type method for solving sparse linear equations and sparse least-squares problems. lusol -- A sparse LU factorization for square and rectangular matrices, with Bartels-Golub-Reid updates for column replacement and other rank-1 modifications. Has a Broyden update option. Has various line search options. use a specified constant step size (0,1] backtracking linesearch method exact linesearch method using fmin minimizer evaluate function at specified fixed points Compiling A Fortran Package Manager file is also included, so that the library and tests cases can be compiled with FPM. For example: fpm build --profile release\nfpm test --profile release By default, the library is built with double precision ( real64 ) real values. Explicitly specifying the real kind can be done using the following preprocessor flags: Preprocessor flag Kind Number of bytes REAL32 real(kind=real32) 4 REAL64 real(kind=real64) 8 REAL128 real(kind=real128) 16 For example, to build a single precision version of the library, use: fpm build --profile release --flag \"-DREAL32\" To use nlesolver within your fpm project, add the following to your fpm.toml file: [dependencies] nlesolver-fortran = { git = \"https://github.com/jacobwilliams/nlesolver-fortran.git\" } Or to use a specific version: [dependencies] nlesolver-fortran = { git = \"https://github.com/jacobwilliams/nlesolver-fortran.git\" , tag = \"1.1.0\" } Note that LAPACK is required to build. The fmin , lsqr , and lusol libraries are also dependencies (which will be automatically downloaded by fpm). Documentation The API documentation for the current master branch can be found here .  This is generated by processing the source files with FORD . License The NLESolver-Fortran source code and related files and documentation are distributed under a permissive free software license (BSD-3). References C. G. Broyden, \" A Class of Methods for Solving Nonlinear Simultaneous Equations \", Math. Comp. 19 (1965), 577-593 L. K. Schubert, \" Modification of a Quasi-Newton Method for Nonlinear Equations with a Sparse Jacobian \", Mathematics of Computation, Vol. 24, No. 109 (Jan., 1970), pp. 27-30. See also MINPACK -- Modernized Minpack: for solving nonlinear equations and nonlinear least squares problems LUSOL Stanford University Systems Optimization Laboratory qr_mumps -- a software package for the solution of sparse, linear\n  systems on multicore computers. Developer Info Jacob Williams","tags":"home","loc":"index.html"},{"title":"nlesolver_type – nlesolver-fortran ","text":"type, public :: nlesolver_type Nonlinear equations solver class. Components Type Visibility Attributes Name Initial integer, private :: n = 0 number of opt vars integer, private :: m = 0 number of constraints integer, private :: max_iter = 100 maximum number of iterations real(kind=wp), private :: tol = 1.0e-6_wp convergence tolerance for function values real(kind=wp), private :: alpha = 1.0_wp step length (when specified constant) real(kind=wp), private :: alpha_min = 0.1_wp minimum step length (when allowed to vary) real(kind=wp), private :: alpha_max = 1.0_wp maximum step length (when allowed to vary) real(kind=wp), private :: tolx = 1.0e-8_wp convergence tolerance for x real(kind=wp), private :: c = 0.5_wp backtracking linesearch parameter (0,1) real(kind=wp), private :: tau = 0.5_wp backtracking linesearch parameter (0,1) real(kind=wp), private :: fmin_tol = 1.0e-5_wp tolerance for \"exact\" linesearch integer, private :: n_intervals = 2 number of intervals for fixed point linesearch logical, private :: use_broyden = .false. if true, a Broyden update is used\nrather than computing the Jacobian\nat every step. The grad function is\nonly called for the initial evaluation. integer, private :: broyden_update_n = 4 if this value is >0 , the Broyden update\nis computed at most this many times before\nthe full Jacobian is recomputed. integer, private :: n_uphill_max = 5 maximum number of consecutive steps\nto allow where the value of f increases logical, private :: verbose = .false. verbose output printing integer, private :: iunit = output_unit output unit for printing (assumed to be open). character(len=:), private, allocatable :: message latest status message integer, private :: istat = -999 latest status message procedure( func_func ), private, pointer :: func => null() user-supplied routine to compute the function procedure( export_func ), private, pointer :: export_iteration => null() user-supplied routine to export iterations procedure( wait_func ), private, pointer :: user_input_check => null() user-supplied routine to enable user to stop iterations procedure( linesearch_func ), private, pointer :: linesearch => null() line search method (determined by step_mode user input in initialize ) integer, private :: sparsity_mode = 1 sparsity mode: 1 - assume dense (use dense solver) 2 - assume sparse (use LSQR sparse solver). 3 - assume sparse (use LUSOL sparse solver). integer, private :: n_nonzeros = -1 number of nonzero Jacobian elements (used for sparsity_mode > 1 ) integer, private, dimension(:), allocatable :: irow sparsity pattern nonzero elements row indices. integer, private, dimension(:), allocatable :: icol sparsity pattern nonzero elements column indices real(kind=wp), private :: atol = zero relative error in definition of A real(kind=wp), private :: btol = zero relative error in definition of b real(kind=wp), private :: conlim = zero An upper limit on cond(Abar) , the apparent\ncondition number of the matrix Abar . integer, private :: itnlim = 100 max iterations integer, private :: nout = 0 output unit for printing real(kind=wp), private :: damp = zero damp parameter for LSQR integer, private :: lusol_method = 0 0 => TPP: Threshold Partial   Pivoting. 1 => TRP: Threshold Rook      Pivoting. 2 => TCP: Threshold Complete  Pivoting. procedure( grad_func ), private, pointer :: grad => null() user-supplied routine to compute the gradient of the function (dense version) procedure( grad_func_sparse ), private, pointer :: grad_sparse => null() user-supplied routine to compute the gradient of the function (sparse version) Type-Bound Procedures procedure, public :: initialize => initialize_nlesolver_variables private  subroutine initialize_nlesolver_variables (me, n, m, max_iter, tol, alpha, alpha_min, alpha_max, tolx, fmin_tol, backtrack_c, backtrack_tau, use_broyden, broyden_update_n, step_mode, func, grad, grad_sparse, export_iteration, user_input_check, verbose, iunit, n_uphill_max, n_intervals, sparsity_mode, irow, icol, atol, btol, conlim, damp, itnlim, nout, lusol_method) Constructor for the class. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(in) :: n number of optimization variables integer, intent(in) :: m number of constraints integer, intent(in) :: max_iter maximum number of iterations real(kind=wp), intent(in) :: tol function convergence tolerance real(kind=wp), intent(in), optional :: alpha constant step length for step_mode=1 (0,1] real(kind=wp), intent(in), optional :: alpha_min minimum step length (0,1] real(kind=wp), intent(in), optional :: alpha_max maximum step length (0,1] real(kind=wp), intent(in), optional :: tolx convergence tolerance for changes in x real(kind=wp), intent(in), optional :: fmin_tol convergence tolerance for fmin (used when step_mode=3 ) real(kind=wp), intent(in), optional :: backtrack_c backtracking linesearch parameter (0,1) real(kind=wp), intent(in), optional :: backtrack_tau backtracking linesearch parameter (0,1) logical, intent(in), optional :: use_broyden use a Broyden update (default is False) integer, intent(in), optional :: broyden_update_n For Broyden mode, update the full Jacobian\nat most every this many iterations (must be >1)\nIf <=1 then Jacobian is only computed on the\nfirst iteration. integer, intent(in), optional :: step_mode step mode: Read more… procedure( func_func ) :: func computes the function vector procedure( grad_func ), optional :: grad computes the jacobian [required for dense mode: sparsity_mode=1 ] procedure( grad_func_sparse ), optional :: grad_sparse computes the jacobian [required for sparse mode: sparsity_mode>1 ] procedure( export_func ), optional :: export_iteration function to export each iteration procedure( wait_func ), optional :: user_input_check check for user input (to stop solver if necessary) logical, intent(in), optional :: verbose for verbose status printing integer, intent(in), optional :: iunit unit for verbose printing (assumed to be open).\nby default this is output_unit . integer, intent(in), optional :: n_uphill_max maximum number of consecutive steps\nto allow where the value of f increases integer, intent(in), optional :: n_intervals number of intervals for fixed point linesearch integer, intent(in), optional :: sparsity_mode sparsity mode: Read more… integer, intent(in), optional, dimension(:) :: irow sparsity pattern nonzero elements row indices.\nmust be specified with icol and be the same length ( n_nonzeros ). integer, intent(in), optional, dimension(:) :: icol sparsity pattern nonzero elements column indices\nmust be specified with icol and be the same length ( n_nonzeros ). real(kind=wp), intent(in), optional :: atol LSQR : relative error in definition of A real(kind=wp), intent(in), optional :: btol LSQR : relative error in definition of b real(kind=wp), intent(in), optional :: conlim LSQR : An upper limit on cond(Abar) , the apparent\ncondition number of the matrix Abar . real(kind=wp), intent(in), optional :: damp LSQR : damp factor integer, intent(in), optional :: itnlim LSQR : max iterations integer, intent(in), optional :: nout LSQR : output unit for printing integer, intent(in), optional :: lusol_method LUSOL method: Read more… procedure, public :: solve => nlesolver_solver private  subroutine nlesolver_solver (me, x) Main solver. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(inout), dimension(:) :: x procedure, public :: destroy => destroy_nlesolver_variables private  subroutine destroy_nlesolver_variables (me) Destructor Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(out) :: me procedure, public :: status => get_status private  subroutine get_status (me, istat, message) Return the status code and message from the nlesolver_type class. Read more… Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(out), optional :: istat Integer status code. character(len=:), intent(out), optional, allocatable :: message Text status message procedure, private :: set_status private  subroutine set_status (me, istat, string, i, r) Set status flag and message. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(in) :: istat status code character(len=*), intent(in) :: string status message integer, intent(in), optional :: i an integer value to append real(kind=wp), intent(in), optional :: r a real value to append Source Code type , public :: nlesolver_type !! Nonlinear equations solver class. private integer :: n = 0 !! number of opt vars integer :: m = 0 !! number of constraints integer :: max_iter = 100 !! maximum number of iterations real ( wp ) :: tol = 1.0e-6_wp !! convergence tolerance for function values real ( wp ) :: alpha = 1.0_wp !! step length (when specified constant) real ( wp ) :: alpha_min = 0.1_wp !! minimum step length (when allowed to vary) real ( wp ) :: alpha_max = 1.0_wp !! maximum step length (when allowed to vary) real ( wp ) :: tolx = 1.0e-8_wp !! convergence tolerance for `x` real ( wp ) :: c = 0.5_wp !! backtracking linesearch parameter (0,1) real ( wp ) :: tau = 0.5_wp !! backtracking linesearch parameter (0,1) real ( wp ) :: fmin_tol = 1.0e-5_wp !! tolerance for \"exact\" linesearch integer :: n_intervals = 2 !! number of intervals for fixed point linesearch logical :: use_broyden = . false . !! if true, a Broyden update is used !! rather than computing the Jacobian !! at every step. The `grad` function is !! only called for the initial evaluation. integer :: broyden_update_n = 4 !! if this value is `>0`, the Broyden update !! is computed at most this many times before !! the full Jacobian is recomputed. integer :: n_uphill_max = 5 !! maximum number of consecutive steps !! to allow where the value of `f` increases logical :: verbose = . false . !! verbose output printing integer :: iunit = output_unit !! output unit for printing (assumed to be open). character ( len = :), allocatable :: message !! latest status message integer :: istat = - 999 !! latest status message procedure ( func_func ), pointer :: func => null () !! user-supplied routine to compute the function procedure ( export_func ), pointer :: export_iteration => null () !! user-supplied routine to export iterations procedure ( wait_func ), pointer :: user_input_check => null () !! user-supplied routine to enable user to stop iterations procedure ( linesearch_func ), pointer :: linesearch => null () !! line search method (determined by `step_mode` user input in [[nlesolver_type:initialize]]) ! sparsity options: integer :: sparsity_mode = 1 !! sparsity mode: !! !! * 1 - assume dense (use dense solver) !! * 2 - assume sparse (use LSQR sparse solver). !! * 3 - assume sparse (use LUSOL sparse solver). integer :: n_nonzeros = - 1 !! number of nonzero Jacobian elements (used for `sparsity_mode > 1`) integer , dimension (:), allocatable :: irow !! sparsity pattern nonzero elements row indices. integer , dimension (:), allocatable :: icol !! sparsity pattern nonzero elements column indices ! LSQR parameters: real ( wp ) :: atol = zero !! relative error in definition of `A` real ( wp ) :: btol = zero !! relative error in definition of `b` real ( wp ) :: conlim = zero !! An upper limit on `cond(Abar)`, the apparent !! condition number of the matrix `Abar`. integer :: itnlim = 100 !! max iterations integer :: nout = 0 !! output unit for printing real ( wp ) :: damp = zero !! damp parameter for LSQR ! LUSOL parameters: integer :: lusol_method = 0 !! * 0 => TPP: Threshold Partial   Pivoting. !! * 1 => TRP: Threshold Rook      Pivoting. !! * 2 => TCP: Threshold Complete  Pivoting. ! dense version: procedure ( grad_func ), pointer :: grad => null () !! user-supplied routine to compute the gradient of the function (dense version) ! sparse version: procedure ( grad_func_sparse ), pointer :: grad_sparse => null () !! user-supplied routine to compute the gradient of the function (sparse version) contains private procedure , public :: initialize => initialize_nlesolver_variables procedure , public :: solve => nlesolver_solver procedure , public :: destroy => destroy_nlesolver_variables procedure , public :: status => get_status procedure :: set_status end type nlesolver_type","tags":"","loc":"type/nlesolver_type.html"},{"title":"func_func – nlesolver-fortran","text":"interface private  subroutine func_func(me, x, f) Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(out), dimension(:) :: f Description compute the function","tags":"","loc":"interface/func_func.html"},{"title":"grad_func – nlesolver-fortran","text":"interface private  subroutine grad_func(me, x, g) Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(out), dimension(:,:) :: g Description compute the gradient of the function (Jacobian). Dense version.","tags":"","loc":"interface/grad_func.html"},{"title":"grad_func_sparse – nlesolver-fortran","text":"interface private  subroutine grad_func_sparse(me, x, g) Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(out), dimension(:) :: g sparse jacobian. length is n_nonzeros Description compute the gradient of the function (Jacobian). Sparse version.","tags":"","loc":"interface/grad_func_sparse.html"},{"title":"export_func – nlesolver-fortran","text":"interface private  subroutine export_func(me, x, f, iter) Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(in), dimension(:) :: f integer, intent(in) :: iter iteration number Description export an iteration:","tags":"","loc":"interface/export_func.html"},{"title":"wait_func – nlesolver-fortran","text":"interface private  subroutine wait_func(me, user_stop) Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me logical, intent(out) :: user_stop Description enable a user-triggered stop of the iterations:","tags":"","loc":"interface/wait_func.html"},{"title":"linesearch_func – nlesolver-fortran","text":"interface private  subroutine linesearch_func(me, xold, p, x, f, fvec, fjac, fjac_sparse) Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f input: current magnitude of fvec , output: new value of f real(kind=wp), intent(inout), dimension(me%m) :: fvec input: current function vector, output: new function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] Description line search method. Note that not all inputs/outputs are\nused by all methods.","tags":"","loc":"interface/linesearch_func.html"},{"title":"set_status – nlesolver-fortran","text":"private  subroutine set_status(me, istat, string, i, r) Set status flag and message. Type Bound nlesolver_type Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(in) :: istat status code character(len=*), intent(in) :: string status message integer, intent(in), optional :: i an integer value to append real(kind=wp), intent(in), optional :: r a real value to append Called by proc~~set_status~~CalledByGraph proc~set_status nlesolver_module::nlesolver_type%set_status proc~initialize_nlesolver_variables nlesolver_module::nlesolver_type%initialize_nlesolver_variables proc~initialize_nlesolver_variables->proc~set_status proc~nlesolver_solver nlesolver_module::nlesolver_type%nlesolver_solver proc~nlesolver_solver->proc~set_status Help Graph Key Nodes of different colours represent the following: Graph Key Subroutine Subroutine Function Function Interface Interface Type Bound Procedure Type Bound Procedure Unknown Procedure Type Unknown Procedure Type Program Program This Page's Entity This Page's Entity Solid arrows point from a procedure to one which it calls. Dashed \narrows point from an interface to procedures which implement that interface.\nThis could include the module procedures in a generic interface or the\nimplementation in a submodule of an interface in a parent module. Source Code subroutine set_status ( me , istat , string , i , r ) implicit none class ( nlesolver_type ), intent ( inout ) :: me integer , intent ( in ) :: istat !! status code character ( len =* ), intent ( in ) :: string !! status message integer , intent ( in ), optional :: i !! an integer value to append real ( wp ), intent ( in ), optional :: r !! a real value to append character ( len = 256 ) :: numstr !! for number fo string conversion character ( len = :), allocatable :: message !! the full message to log integer :: iostat !! write `iostat` code message = trim ( string ) if ( present ( i )) then numstr = '' write ( numstr , fmt =* , iostat = iostat ) i if ( iostat /= 0 ) numstr = '****' message = message // ' ' // trim ( adjustl ( numstr )) end if if ( present ( r )) then numstr = '' write ( numstr , fmt =* , iostat = iostat ) r if ( iostat /= 0 ) numstr = '****' message = message // ' ' // trim ( adjustl ( numstr )) end if if ( me % verbose ) then write ( me % iunit , '(A)' , iostat = iostat ) message end if ! store in the class: me % istat = istat me % message = message end subroutine set_status","tags":"","loc":"proc/set_status.html"},{"title":"get_status – nlesolver-fortran","text":"private  subroutine get_status(me, istat, message) Return the status code and message from the nlesolver_type class. Status codes -1   -- Error: Invalid alpha -2   -- Error: Invalid alpha_min -3   -- Error: Invalid alpha_max -4   -- Error: Alpha_min must be < alpha_max -5   -- Error: Invalid step_mode -6   -- Error solving linear system -7   -- Error: More than 5 steps in the uphill direction -8   -- Error: Divide by zero when computing Broyden update -9   -- Error: Out of memory -10  -- Error: function routine is not associated -11  -- Error: gradient routine is not associated -12  -- Error: backtracking linesearch c must be in range (0, 1) -13  -- Error: backtracking linesearch tau must be in range (0, 1) -14  -- Error: must specify grad_sparse, irow, and icol for sparsity_mode > 1 -15  -- Error: irow and icol must be the same length -999 -- Error: class has not been initialized 0    -- Class successfully initialized in initialize 1    -- Required accuracy achieved 2    -- Solution cannot be improved 3    -- Maximum number of iterations reached 4    -- Stopped by the user Type Bound nlesolver_type Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(out), optional :: istat Integer status code. character(len=:), intent(out), optional, allocatable :: message Text status message Source Code subroutine get_status ( me , istat , message ) implicit none class ( nlesolver_type ), intent ( inout ) :: me integer , intent ( out ), optional :: istat !! Integer status code. character ( len = :), allocatable , intent ( out ), optional :: message !! Text status message if ( present ( istat )) istat = me % istat if ( present ( message )) then if ( allocated ( me % message )) then message = trim ( me % message ) else message = 'Error: class has not been initialized' end if end if end subroutine get_status","tags":"","loc":"proc/get_status.html"},{"title":"initialize_nlesolver_variables – nlesolver-fortran","text":"private  subroutine initialize_nlesolver_variables(me, n, m, max_iter, tol, alpha, alpha_min, alpha_max, tolx, fmin_tol, backtrack_c, backtrack_tau, use_broyden, broyden_update_n, step_mode, func, grad, grad_sparse, export_iteration, user_input_check, verbose, iunit, n_uphill_max, n_intervals, sparsity_mode, irow, icol, atol, btol, conlim, damp, itnlim, nout, lusol_method) Constructor for the class. Type Bound nlesolver_type Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(in) :: n number of optimization variables integer, intent(in) :: m number of constraints integer, intent(in) :: max_iter maximum number of iterations real(kind=wp), intent(in) :: tol function convergence tolerance real(kind=wp), intent(in), optional :: alpha constant step length for step_mode=1 (0,1] real(kind=wp), intent(in), optional :: alpha_min minimum step length (0,1] real(kind=wp), intent(in), optional :: alpha_max maximum step length (0,1] real(kind=wp), intent(in), optional :: tolx convergence tolerance for changes in x real(kind=wp), intent(in), optional :: fmin_tol convergence tolerance for fmin (used when step_mode=3 ) real(kind=wp), intent(in), optional :: backtrack_c backtracking linesearch parameter (0,1) real(kind=wp), intent(in), optional :: backtrack_tau backtracking linesearch parameter (0,1) logical, intent(in), optional :: use_broyden use a Broyden update (default is False) integer, intent(in), optional :: broyden_update_n For Broyden mode, update the full Jacobian\nat most every this many iterations (must be >1)\nIf <=1 then Jacobian is only computed on the\nfirst iteration. integer, intent(in), optional :: step_mode step mode: 1 = use the specified alpha (0,1] 2 = backtracking linesearch (between alpha_min and alpha_max ) 3 = exact linesearch (between alpha_min and alpha_max ) 4 = evaluate function at specified fixed points  (between alpha_min and alpha_max ) procedure( func_func ) :: func computes the function vector procedure( grad_func ), optional :: grad computes the jacobian [required for dense mode: sparsity_mode=1 ] procedure( grad_func_sparse ), optional :: grad_sparse computes the jacobian [required for sparse mode: sparsity_mode>1 ] procedure( export_func ), optional :: export_iteration function to export each iteration procedure( wait_func ), optional :: user_input_check check for user input (to stop solver if necessary) logical, intent(in), optional :: verbose for verbose status printing integer, intent(in), optional :: iunit unit for verbose printing (assumed to be open).\nby default this is output_unit . integer, intent(in), optional :: n_uphill_max maximum number of consecutive steps\nto allow where the value of f increases integer, intent(in), optional :: n_intervals number of intervals for fixed point linesearch integer, intent(in), optional :: sparsity_mode sparsity mode: 1 - assume dense (use dense solver)\n  Must specify grad for this mode. 2 - assume sparse (use LSQR sparse solver). 3 - assume sparse (use LUSOL sparse solver).\nMust also specify grad_sparse and the irow and icol sparsity pattern for mode>1 . integer, intent(in), optional, dimension(:) :: irow sparsity pattern nonzero elements row indices.\nmust be specified with icol and be the same length ( n_nonzeros ). integer, intent(in), optional, dimension(:) :: icol sparsity pattern nonzero elements column indices\nmust be specified with icol and be the same length ( n_nonzeros ). real(kind=wp), intent(in), optional :: atol LSQR : relative error in definition of A real(kind=wp), intent(in), optional :: btol LSQR : relative error in definition of b real(kind=wp), intent(in), optional :: conlim LSQR : An upper limit on cond(Abar) , the apparent\ncondition number of the matrix Abar . real(kind=wp), intent(in), optional :: damp LSQR : damp factor integer, intent(in), optional :: itnlim LSQR : max iterations integer, intent(in), optional :: nout LSQR : output unit for printing integer, intent(in), optional :: lusol_method LUSOL method: 0 => TPP: Threshold Partial   Pivoting. 1 => TRP: Threshold Rook      Pivoting. 2 => TCP: Threshold Complete  Pivoting. Calls proc~~initialize_nlesolver_variables~~CallsGraph proc~initialize_nlesolver_variables nlesolver_module::nlesolver_type%initialize_nlesolver_variables proc~set_status nlesolver_module::nlesolver_type%set_status proc~initialize_nlesolver_variables->proc~set_status Help Graph Key Nodes of different colours represent the following: Graph Key Subroutine Subroutine Function Function Interface Interface Type Bound Procedure Type Bound Procedure Unknown Procedure Type Unknown Procedure Type Program Program This Page's Entity This Page's Entity Solid arrows point from a procedure to one which it calls. Dashed \narrows point from an interface to procedures which implement that interface.\nThis could include the module procedures in a generic interface or the\nimplementation in a submodule of an interface in a parent module. Source Code subroutine initialize_nlesolver_variables ( me ,& n , m , max_iter , tol , alpha , alpha_min , alpha_max , tolx , fmin_tol ,& backtrack_c , backtrack_tau ,& use_broyden , broyden_update_n , step_mode ,& func , grad , grad_sparse ,& export_iteration , user_input_check ,& verbose , iunit , n_uphill_max , n_intervals ,& sparsity_mode , irow , icol ,& atol , btol , conlim , damp , itnlim , nout ,& lusol_method ) implicit none class ( nlesolver_type ), intent ( inout ) :: me integer , intent ( in ) :: n !! number of optimization variables integer , intent ( in ) :: m !! number of constraints integer , intent ( in ) :: max_iter !! maximum number of iterations real ( wp ), intent ( in ) :: tol !! function convergence tolerance procedure ( func_func ) :: func !! computes the function vector procedure ( grad_func ), optional :: grad !! computes the jacobian [required for dense mode: `sparsity_mode=1`] procedure ( grad_func_sparse ), optional :: grad_sparse !! computes the jacobian [required for sparse mode: `sparsity_mode>1`] integer , intent ( in ), optional :: step_mode !! step mode: !! !!  * 1 = use the specified `alpha` (0,1] !!  * 2 = backtracking linesearch (between `alpha_min` and `alpha_max`) !!  * 3 = exact linesearch (between `alpha_min` and `alpha_max`) !!  * 4 = evaluate function at specified fixed points  (between `alpha_min` and `alpha_max`) real ( wp ), intent ( in ), optional :: alpha !! constant step length for `step_mode=1` (0,1] real ( wp ), intent ( in ), optional :: alpha_min !! minimum step length (0,1] real ( wp ), intent ( in ), optional :: alpha_max !! maximum step length (0,1] real ( wp ), intent ( in ), optional :: tolx !! convergence tolerance for changes in `x` real ( wp ), intent ( in ), optional :: fmin_tol !! convergence tolerance for [[fmin]] (used when `step_mode=3`) real ( wp ), intent ( in ), optional :: backtrack_c !! backtracking linesearch parameter (0,1) real ( wp ), intent ( in ), optional :: backtrack_tau !! backtracking linesearch parameter (0,1) logical , intent ( in ), optional :: use_broyden !! use a Broyden update (default is False) integer , intent ( in ), optional :: broyden_update_n !! For Broyden mode, update the full Jacobian !! at most every this many iterations (must be >1) !! If <=1 then Jacobian is only computed on the !! first iteration. procedure ( export_func ), optional :: export_iteration !! function to export each iteration procedure ( wait_func ), optional :: user_input_check !! check for user input (to stop solver if necessary) logical , intent ( in ), optional :: verbose !! for verbose status printing integer , intent ( in ), optional :: iunit !! unit for verbose printing (assumed to be open). !! by default this is `output_unit`. integer , intent ( in ), optional :: n_uphill_max !! maximum number of consecutive steps !! to allow where the value of `f` increases integer , intent ( in ), optional :: n_intervals !! number of intervals for fixed point linesearch integer , intent ( in ), optional :: sparsity_mode !! sparsity mode: !! !! * 1 - assume dense (use dense solver) !!   Must specify `grad` for this mode. !! * 2 - assume sparse (use LSQR sparse solver). !! * 3 - assume sparse (use LUSOL sparse solver). !! Must also specify `grad_sparse` and the `irow` and `icol` !! sparsity pattern for `mode>1`. integer , dimension (:), intent ( in ), optional :: irow !! sparsity pattern nonzero elements row indices. !! must be specified with `icol` and be the same length (`n_nonzeros`). integer , dimension (:), intent ( in ), optional :: icol !! sparsity pattern nonzero elements column indices !! must be specified with `icol` and be the same length (`n_nonzeros`). real ( wp ), intent ( in ), optional :: atol !! `LSQR`: relative error in definition of `A` real ( wp ), intent ( in ), optional :: btol !! `LSQR`: relative error in definition of `b` real ( wp ), intent ( in ), optional :: conlim !! `LSQR`: An upper limit on `cond(Abar)`, the apparent !! condition number of the matrix `Abar`. real ( wp ), intent ( in ), optional :: damp !! `LSQR`: damp factor integer , intent ( in ), optional :: itnlim !! `LSQR`: max iterations integer , intent ( in ), optional :: nout !! `LSQR`: output unit for printing integer , intent ( in ), optional :: lusol_method !! `LUSOL` method: !! !! * 0 => TPP: Threshold Partial   Pivoting. !! * 1 => TRP: Threshold Rook      Pivoting. !! * 2 => TCP: Threshold Complete  Pivoting. logical :: status_ok !! true if there were no errors status_ok = . true . !required: me % n = abs ( n ) me % m = abs ( m ) me % max_iter = abs ( max_iter ) me % tol = abs ( tol ) me % func => func if ( present ( grad )) me % grad => grad if ( present ( grad_sparse )) me % grad_sparse => grad_sparse !optional: if ( present ( step_mode )) then select case ( step_mode ) case ( 1 ) ! = use the specified `alpha` (0,1] me % linesearch => simple_step case ( 2 ) ! = backtracking linesearch (between `alpha_min` and `alpha_max`) me % linesearch => backtracking_linesearch case ( 3 ) ! = exact linesearch (between `alpha_min` and `alpha_max`) me % linesearch => exact_linesearch case ( 4 ) ! = evaluate function at specified fixed points (between `alpha_min` and `alpha_max`) me % linesearch => fixed_point_linesearch case default status_ok = . false . call me % set_status ( istat = - 5 , string = 'Error: invalid step_mode:' , i = step_mode ) return end select else me % linesearch => simple_step end if if ( present ( alpha )) me % alpha = abs ( alpha ) if ( present ( alpha_min )) me % alpha_min = abs ( alpha_min ) if ( present ( alpha_max )) me % alpha_max = abs ( alpha_max ) if ( present ( tolx )) me % tolx = abs ( tolx ) if ( present ( backtrack_c )) me % c = abs ( backtrack_c ) if ( present ( backtrack_tau )) me % tau = abs ( backtrack_tau ) if ( present ( use_broyden )) me % use_broyden = use_broyden if ( present ( broyden_update_n )) me % broyden_update_n = abs ( broyden_update_n ) if ( present ( verbose )) me % verbose = verbose if ( present ( iunit )) me % iunit = iunit if ( present ( n_uphill_max )) me % n_uphill_max = abs ( n_uphill_max ) if ( present ( n_intervals )) me % n_intervals = max ( abs ( n_intervals ), 1 ) if ( present ( fmin_tol )) me % fmin_tol = abs ( fmin_tol ) if ( present ( export_iteration )) me % export_iteration => export_iteration if ( present ( user_input_check )) me % user_input_check => user_input_check ! error checks: if ( me % alpha < zero . or . me % alpha > one ) then status_ok = . false . call me % set_status ( istat = - 1 , string = 'Error: invalid alpha:' , r = me % alpha ) return end if if ( me % alpha_min < zero . or . me % alpha_min > one ) then status_ok = . false . call me % set_status ( istat = - 2 , string = 'Error: invalid alpha_min:' , r = me % alpha_min ) return end if if ( me % alpha_max < zero . or . me % alpha_max > one ) then status_ok = . false . call me % set_status ( istat = - 3 , string = 'Error: invalid alpha_max:' , r = me % alpha_max ) return end if if ( me % alpha_max <= me % alpha_min ) then status_ok = . false . call me % set_status ( istat = - 4 , string = 'Error: alpha_min must be < alpha_max' ) return end if if ( me % c < zero . or . me % c > one ) then status_ok = . false . call me % set_status ( istat = - 12 , string = 'Error: backtracking linesearch c must be in range (0, 1):' , r = me % c ) return end if if ( me % tau < zero . or . me % tau > one ) then status_ok = . false . call me % set_status ( istat = - 13 , string = 'Error: backtracking linesearch tau must be in range (0, 1):' , r = me % tau ) return end if ! initialize: me % n_nonzeros = - 1 ! not used if ( allocated ( me % irow )) deallocate ( me % irow ) if ( allocated ( me % icol )) deallocate ( me % icol ) if ( present ( sparsity_mode )) then me % sparsity_mode = sparsity_mode if ( sparsity_mode > 1 ) then ! sparse solver method if ( present ( irow ) . and . present ( icol ) . and . present ( grad_sparse )) then if ( size ( irow ) == size ( icol )) then me % n_nonzeros = size ( irow ) me % irow = irow me % icol = icol else call me % set_status ( istat = - 15 , string = 'Error: irow and icol must be the same length' ) return end if else call me % set_status ( istat = - 14 , string = 'Error: must specify grad_sparse, irow, and icol for sparsity_mode > 1' ) return end if ! LSQR optional inputs: if ( present ( atol )) me % atol = atol if ( present ( btol )) me % btol = btol if ( present ( conlim )) me % conlim = conlim if ( present ( damp )) me % damp = damp if ( present ( itnlim )) me % itnlim = itnlim if ( present ( nout )) me % nout = nout ! LUSOL method if ( present ( nout )) me % lusol_method = lusol_method end if end if if ( status_ok ) then call me % set_status ( istat = 0 , string = 'Class successfully initialized' ) end if end subroutine initialize_nlesolver_variables","tags":"","loc":"proc/initialize_nlesolver_variables.html"},{"title":"nlesolver_solver – nlesolver-fortran","text":"private  subroutine nlesolver_solver(me, x) Main solver. Type Bound nlesolver_type Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(inout), dimension(:) :: x Calls proc~~nlesolver_solver~~CallsGraph proc~nlesolver_solver nlesolver_module::nlesolver_type%nlesolver_solver initialize initialize proc~nlesolver_solver->initialize proc~linear_solver nlesolver_module::linear_solver proc~nlesolver_solver->proc~linear_solver proc~set_status nlesolver_module::nlesolver_type%set_status proc~nlesolver_solver->proc~set_status solve solve proc~nlesolver_solver->solve Help Graph Key Nodes of different colours represent the following: Graph Key Subroutine Subroutine Function Function Interface Interface Type Bound Procedure Type Bound Procedure Unknown Procedure Type Unknown Procedure Type Program Program This Page's Entity This Page's Entity Solid arrows point from a procedure to one which it calls. Dashed \narrows point from an interface to procedures which implement that interface.\nThis could include the module procedures in a generic interface or the\nimplementation in a submodule of an interface in a parent module. Source Code subroutine nlesolver_solver ( me , x ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension (:), intent ( inout ) :: x real ( wp ), dimension (:) , allocatable :: fvec !! function vector real ( wp ), dimension (:,:), allocatable :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), allocatable :: fjac_sparse !! jacobian matrix [sparse] real ( wp ), dimension (:), allocatable :: prev_fjac_sparse !! previous jacobian matrix [sparse] real ( wp ), dimension (:) , allocatable :: rhs !! linear system right-hand side real ( wp ), dimension (:) , allocatable :: p !! search direction real ( wp ), dimension (:) , allocatable :: xold !! previous value of `x` real ( wp ), dimension (:) , allocatable :: prev_fvec !! previous function vector real ( wp ), dimension (:,:), allocatable :: prev_fjac !! previous jacobian matrix real ( wp ), dimension (:,:), allocatable :: delf !! used for Broyden (rank 2 for `matmul`) real ( wp ), dimension (:,:), allocatable :: delx !! used for Broyden (rank 2 for `matmul`) logical :: user_stop !! user stop button flag integer :: info !! status flag from the [[linear_solver]] integer :: iter !! iteration counter real ( wp ) :: f !! magnitude of `fvec` real ( wp ) :: fold !! previous value of `f` integer :: n_uphill !! number of steps taken in the \"uphill\" direction !! (where `f` is increasing) real ( wp ) :: delxmag2 !! used for Broyden logical :: recompute_jac !! if using Broyden, and we want to call the user !! jacobian routine instead integer :: broyden_counter !! number of times the broyden update has been used integer :: alloc_stat !! allocation status flag type ( lsqr_solver_ez ) :: sparse_solver !! sparse LSQR solver class type ( lusol_settings ) :: lusol_options integer :: i !! counter integer , dimension (:), allocatable :: idx , index_array !! for sparse indexing character ( len = 10 ) :: i_str !! string version of `i` for row string if ( me % istat < 0 ) return ! class was not initialized properly if (. not . associated ( me % func )) then call me % set_status ( istat = - 10 , string = 'Error: function routine is not associated' ) return end if if ( me % sparsity_mode == 1 . and . . not . associated ( me % grad )) then call me % set_status ( istat = - 11 , string = 'Error: gradient routine is not associated' ) return end if if ( me % sparsity_mode > 1 . and . . not . associated ( me % grad_sparse )) then call me % set_status ( istat = - 11 , string = 'Error: gradient routine is not associated' ) return end if ! initialize: iter = 0 n_uphill = 0 recompute_jac = . false . broyden_counter = 0 ! allocate the arrays: alloc_stat = 0 if ( alloc_stat == 0 ) allocate ( fvec ( me % m ) , stat = alloc_stat ) if ( me % sparsity_mode == 1 ) then ! dense if ( alloc_stat == 0 ) allocate ( fjac ( me % m , me % n ) , stat = alloc_stat ) else ! sparse if ( alloc_stat == 0 ) allocate ( fjac_sparse ( me % n_nonzeros ) , stat = alloc_stat ) if ( me % use_broyden . and . alloc_stat == 0 ) allocate ( prev_fjac_sparse ( me % n_nonzeros ) , stat = alloc_stat ) end if if ( alloc_stat == 0 ) allocate ( rhs ( me % m ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( p ( me % n ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( xold ( me % n ) , stat = alloc_stat ) if ( me % use_broyden ) then ! only need these for broyden: if ( alloc_stat == 0 ) allocate ( prev_fvec ( me % m ) , stat = alloc_stat ) if ( me % sparsity_mode /= 1 . and . alloc_stat == 0 ) then allocate ( prev_fjac ( me % m , me % n ) , stat = alloc_stat ) index_array = [( i , i = 1 , me % n_nonzeros )] ! an array to index the sparse jacobian elements end if if ( alloc_stat == 0 ) allocate ( delf ( me % m , 1 ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( delx ( me % n , 1 ) , stat = alloc_stat ) end if if ( alloc_stat /= 0 ) then call me % set_status ( istat = - 9 , string = 'Error: Out of memory' ) return else me % istat = - 998 me % message = 'Unknown error' end if ! evaluate the function: call me % func ( x , fvec ) f = norm2 ( fvec ) ! check to see if initial guess is a root: if ( f <= me % tol ) then call me % set_status ( istat = 1 , string = 'Required accuracy achieved' ) else ! main iteration loop: do iter = 1 , me % max_iter ! Export the current iteration: if ( associated ( me % export_iteration )) call me % export_iteration ( x , fvec , iter ) ! Check for user stop: if ( associated ( me % user_input_check )) then call me % user_input_check ( user_stop ) if ( user_stop ) then call me % set_status ( istat = 4 , string = 'Stopped by the user' ) exit end if end if if ( me % use_broyden . and . . not . recompute_jac ) then if ( iter == 1 ) then ! always compute Jacobian on the first iteration !call me%grad(x,fjac) select case ( me % sparsity_mode ) case ( 1 ) call me % grad ( x , fjac ) case ( 2 :) call me % grad_sparse ( x , fjac_sparse ) end select broyden_counter = 0 else ! and use Broyden update to estimate Jacobian ! for subsequent iterations. ! note: fvec was computed the last iteration delx (:, 1 ) = x - xold delf (:, 1 ) = fvec - prev_fvec if ( me % sparsity_mode == 1 ) then ! dense delxmag2 = dot_product ( delx (:, 1 ), delx (:, 1 )) if ( delxmag2 < eps ) then call me % set_status ( istat = - 8 , & string = 'Error: Divide by zero when computing Broyden update' ) exit end if ! Jacobian estimate: ! This is the equation from wikipedia : https://en.wikipedia.org/wiki/Broyden%27s_method fjac = prev_fjac + matmul (( delf - matmul ( prev_fjac , delx )), transpose ( delx )) / delxmag2 ! see also: eqn 4 in Schubert, which is different ... else ! using a sparse option ! Just a row-by-row version of the fjac equation above. ! see L.K. Schubert, 1970 do i = 1 , me % m idx = pack ( index_array , mask = me % irow == i ) ! the nonzero elements in this row if ( size ( idx ) == 0 ) cycle ! no non-zeros in this row associate ( dx => delx ( me % icol ( idx ),:)) ! nonzero x vec for this row delxmag2 = dot_product ( dx (:, 1 ), dx (:, 1 )) ! only those x's for this row if ( delxmag2 < eps ) then write ( i_str , '(I10)' ) i call me % set_status ( istat = - 8 , & string = 'Error: Divide by zero when computing sparse Broyden update for row ' // & trim ( adjustl ( i_str ))) exit end if fjac_sparse ( idx ) = prev_fjac_sparse ( idx ) + & matmul (( delf ( i , 1 ) - matmul ( prev_fjac_sparse ( idx ), dx )), transpose ( dx )) / delxmag2 end associate end do end if broyden_counter = broyden_counter + 1 end if prev_fvec = fvec if ( me % sparsity_mode == 1 ) then prev_fjac = fjac else prev_fjac_sparse = fjac_sparse end if else ! compute the jacobian: select case ( me % sparsity_mode ) case ( 1 ) call me % grad ( x , fjac ) case ( 2 :) call me % grad_sparse ( x , fjac_sparse ) end select recompute_jac = . false . ! for broyden broyden_counter = 0 end if xold = x fold = f ! compute the search direction p by solving linear system: rhs = - fvec ! RHS of the linear system select case ( me % sparsity_mode ) case ( 1 ) ! use dense solver call linear_solver ( me % m , me % n , fjac , rhs , p , info ) case ( 2 ) ! initialize the LSQR sparse solver call sparse_solver % initialize ( me % m , me % n , fjac_sparse , me % irow , me % icol ,& atol = me % atol , & btol = me % btol , & conlim = me % conlim , & itnlim = me % itnlim , & nout = me % nout ) call sparse_solver % solve ( rhs , me % damp , p , info ) ! solve the linear system ! check convergence: select case ( info ) case ( 4 ) call me % set_status ( istat = - 1004 , & string = 'LSQR Error: The system appears to be ill-conditioned. istop =' , i = info ) exit case ( 5 ) call me % set_status ( istat = - 1005 , & string = 'LSQR Error: The iteration limit was reached. istop =' , i = info ) exit case default info = 0 end select case ( 3 ) ! use lusol solver lusol_options % method = me % lusol_method call solve ( me % n , me % m , me % n_nonzeros , me % irow , me % icol , fjac_sparse , rhs , p , info ,& settings = lusol_options ) end select ! check for errors: if ( info /= 0 ) then call me % set_status ( istat = - 6 , string = 'Error solving linear system. info =' , i = info ) exit else ! next step, using the specified method: call me % linesearch ( xold , p , x , f , fvec , fjac , fjac_sparse ) ! keep track of the number of steps in the \"uphill\" direction: if ( f > fold ) then n_uphill = n_uphill + 1 else n_uphill = 0 end if ! check for stopping conditions if ( f <= me % tol ) then call me % set_status ( istat = 1 , string = 'Required accuracy achieved' ) exit elseif ( maxval ( abs ( x - xold )) <= me % tolx ) then call me % set_status ( istat = 2 , string = 'Solution cannot be improved' ) exit elseif ( iter == me % max_iter ) then call me % set_status ( istat = 3 , string = 'Maximum number of iterations reached' ) exit elseif ( n_uphill > me % n_uphill_max ) then call me % set_status ( istat = 5 , string = 'Too many steps in the uphill direction' ) exit elseif ( me % use_broyden ) then ! If delxmag2 is too small when using broyden, just ! call the user-supplied jacobian function to avoid ! a divide by zero on the next step. This should ! normally only happen when the solution is almost converged. if ( norm2 ( x - xold ) ** 2 <= eps ) then recompute_jac = . true . else if ( me % broyden_update_n > 0 ) then ! Note that we also recompute if we have taken an uphill step if ( broyden_counter == me % broyden_update_n . or . n_uphill > 0 ) then ! time to recompute the full jacobian recompute_jac = . true . end if end if end if endif end if end do !end of iterations loop end if !Export the last iteration: iter = iter + 1 if ( associated ( me % export_iteration )) call me % export_iteration ( x , fvec , iter ) end subroutine nlesolver_solver","tags":"","loc":"proc/nlesolver_solver.html"},{"title":"destroy_nlesolver_variables – nlesolver-fortran","text":"private  subroutine destroy_nlesolver_variables(me) Destructor Type Bound nlesolver_type Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(out) :: me Source Code subroutine destroy_nlesolver_variables ( me ) implicit none class ( nlesolver_type ), intent ( out ) :: me me % message = 'Error: class has not been initialized' me % istat = - 999 end subroutine destroy_nlesolver_variables","tags":"","loc":"proc/destroy_nlesolver_variables.html"},{"title":"linear_solver – nlesolver-fortran","text":"private  subroutine linear_solver(m, n, a, b, x, info) Solve the linear system: , using a dense, direct method. if n=m : use LAPACK dgesv (LU decomposition) if n/=m : use LAPACK dgels (if m>n uses QR factorization,\n  if m<n uses LQ factorization) Arguments Type Intent Optional Attributes Name integer, intent(in) :: m number of rows in a integer, intent(in) :: n number of columns in a real(kind=wp), intent(in), dimension(m,n) :: a A matrix of the linear system real(kind=wp), intent(in), dimension(m) :: b RHS of the linear system real(kind=wp), intent(out), dimension(n) :: x the solution of the linear system. integer, intent(out) :: info output status flag ( =0 if success) Called by proc~~linear_solver~~CalledByGraph proc~linear_solver nlesolver_module::linear_solver proc~nlesolver_solver nlesolver_module::nlesolver_type%nlesolver_solver proc~nlesolver_solver->proc~linear_solver Help Graph Key Nodes of different colours represent the following: Graph Key Subroutine Subroutine Function Function Interface Interface Type Bound Procedure Type Bound Procedure Unknown Procedure Type Unknown Procedure Type Program Program This Page's Entity This Page's Entity Solid arrows point from a procedure to one which it calls. Dashed \narrows point from an interface to procedures which implement that interface.\nThis could include the module procedures in a generic interface or the\nimplementation in a submodule of an interface in a parent module. Source Code subroutine linear_solver ( m , n , a , b , x , info ) implicit none integer , intent ( in ) :: n !! number of columns in `a` integer , intent ( in ) :: m !! number of rows in `a` real ( wp ), dimension ( m , n ), intent ( in ) :: a !! `A` matrix of the linear system real ( wp ), dimension ( m ), intent ( in ) :: b !! RHS of the linear system real ( wp ), dimension ( n ), intent ( out ) :: x !! the solution of the linear system. integer , intent ( out ) :: info !! output status flag (`=0` if success) ! LAPACK routine interfaces: interface subroutine dgesv ( n , nrhs , a , lda , ipiv , b , ldb , info ) !! See: [?gesv](https://www.intel.com/content/www/us/en/develop/documentation/onemkl-developer-reference-fortran/top/lapack-routines/lapack-linear-equation-routines/lapack-linear-equation-driver-routines/gesv.html) import :: wp implicit none integer :: info integer :: lda integer :: ldb integer :: n integer :: nrhs integer :: ipiv ( * ) real ( wp ) :: a ( lda , * ) real ( wp ) :: b ( ldb , * ) end subroutine dgesv subroutine dgels ( trans , m , n , nrhs , a , lda , b , ldb , work , lwork , info ) !! See: [?gels](https://www.intel.com/content/www/us/en/develop/documentation/onemkl-developer-reference-fortran/top/lapack-routines/lapack-least-squares-and-eigenvalue-problem/lapack-least-squares-eigenvalue-problem-driver/linear-least-squares-lls-problems-lapack-driver/gels.html) import :: wp implicit none character :: trans integer :: info integer :: lda integer :: ldb integer :: lwork integer :: m integer :: n integer :: nrhs real ( wp ) :: a ( lda , * ) real ( wp ) :: b ( ldb , * ) real ( wp ) :: work ( * ) end subroutine dgels end interface integer , dimension (:), allocatable :: ipiv !! pivot indices array real ( wp ), dimension (:,:), allocatable :: bmat !! copy of `b` so it won't be overwritten real ( wp ), dimension (:), allocatable :: work !! work array for `dgels` real ( wp ), dimension (:,:), allocatable :: amat !! copy of `a` so it won't be overwritten integer :: lwork !! size of `work` allocate ( amat ( m , n )) allocate ( bmat ( max ( 1 , m , n ), 1 )) if ( n == m ) then !normal inverse allocate ( ipiv ( n )) amat = a bmat ( 1 : n , 1 ) = b call dgesv ( n , 1 , amat , n , ipiv , bmat , n , info ) x = bmat ( 1 : n , 1 ) else amat = a bmat = zero bmat ( 1 : m , 1 ) = b lwork = min ( m , n ) + max ( 1 , m , n ) allocate ( work ( lwork )) call dgels ( 'N' , m , n , 1 , amat , m , bmat , max ( 1 , m , n ), work , lwork , info ) x = bmat ( 1 : n , 1 ) end if end subroutine linear_solver","tags":"","loc":"proc/linear_solver.html"},{"title":"simple_step – nlesolver-fortran","text":"private  subroutine simple_step(me, xold, p, x, f, fvec, fjac, fjac_sparse) Take a simple step in the search direction of p * alpha . Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] Source Code subroutine simple_step ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] x = xold + p * me % alpha !evaluate the function at the new point: call me % func ( x , fvec ) f = norm2 ( fvec ) end subroutine simple_step","tags":"","loc":"proc/simple_step.html"},{"title":"backtracking_linesearch – nlesolver-fortran","text":"private  subroutine backtracking_linesearch(me, xold, p, x, f, fvec, fjac, fjac_sparse) Backtracking line search. See also Backtracking line search Note Either fjac or fjac_sparse should be present. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] Source Code subroutine backtracking_linesearch ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] integer :: i !! counter real ( wp ) :: slope !! local slope of the function of `alpha` along the search direction used for line search logical :: min_alpha_reached !! if the minimum step size is reached during the line search real ( wp ) :: alpha !! `alpha` for the line search real ( wp ) :: ftmp !! `f` value for linesearch real ( wp ) :: t !! used for line search real ( wp ), dimension (:), allocatable :: gradf !! line search objective function gradient vector real ( wp ), dimension (:), allocatable :: xtmp !! `x` value for linesearch real ( wp ), dimension (:), allocatable :: fvectmp !! `fvec` value for linesearch ! allocate arrays: allocate ( gradf ( me % n )) allocate ( xtmp ( me % n )) allocate ( fvectmp ( me % m )) ! compute the gradient of the function to be minimized ! (which in this case is 1/2 the norm of fvec). Use the chain ! rule and the Jacobian matrix already computed. if ( present ( fjac )) then ! dense do i = 1 , me % n gradf ( i ) = dot_product ( fvec , fjac (:, i )) end do else ! sparse do i = 1 , me % n gradf ( i ) = dot_product ( fvec , pack ( fjac_sparse , mask = me % icol == i )) end do end if slope = dot_product ( p , gradf ) t = - me % c * slope if ( me % verbose ) then write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        slope    = ' , slope write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        t        = ' , t end if ! perform the line search: min_alpha_reached = . false . alpha = me % alpha_max ! start with the largest step do xtmp = xold + p * alpha call me % func ( xtmp , fvectmp ) ftmp = norm2 ( fvectmp ) if ( me % verbose ) then write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        alpha    = ' , alpha , ' f       = ' , ftmp if ( f - ftmp >= alpha * t ) then write ( me % iunit , '(1P,2(A,1X,E16.6),1X,A)' ) '        f - ftmp = ' , f - ftmp , ' alpha*t = ' , alpha * t , ' [ACCEPTED]' else write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        f - ftmp = ' , f - ftmp , ' alpha*t = ' , alpha * t end if end if if ((( f - ftmp ) / 2.0_wp >= alpha * t ) . or . min_alpha_reached ) then if ( me % verbose . and . min_alpha_reached ) then write ( me % iunit , '(A)' ) '        Minimum alpha reached' end if ! Armijo-Goldstein condition is satisfied ! (or the min step has been reached) x = xtmp fvec = fvectmp f = ftmp exit end if alpha = alpha * me % tau ! reduce step size if ( alpha <= me % alpha_min ) then alpha = me % alpha_min min_alpha_reached = . true . ! will stop on the next step end if end do end subroutine backtracking_linesearch","tags":"","loc":"proc/backtracking_linesearch.html"},{"title":"exact_linesearch – nlesolver-fortran","text":"private  subroutine exact_linesearch(me, xold, p, x, f, fvec, fjac, fjac_sparse) An exact linesearch that uses a derivative-free minimizer to\nfind the minimum value of f(x) between x = xold + p * alpha_min and x = xold + p * alpha_max . Usually this is overkill and not necessary, but is here as an option for testing. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] Calls proc~~exact_linesearch~~CallsGraph proc~exact_linesearch nlesolver_module::exact_linesearch fmin fmin proc~exact_linesearch->fmin Help Graph Key Nodes of different colours represent the following: Graph Key Subroutine Subroutine Function Function Interface Interface Type Bound Procedure Type Bound Procedure Unknown Procedure Type Unknown Procedure Type Program Program This Page's Entity This Page's Entity Solid arrows point from a procedure to one which it calls. Dashed \narrows point from an interface to procedures which implement that interface.\nThis could include the module procedures in a generic interface or the\nimplementation in a submodule of an interface in a parent module. Source Code subroutine exact_linesearch ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] real ( wp ), dimension (:), allocatable :: xnew !! used in [[func_for_fmin]] real ( wp ) :: alpha_min allocate ( xnew ( me % n )) ! find the minimum value of f in the range of alphas: alpha_min = fmin ( func_for_fmin , me % alpha_min , me % alpha_max , me % fmin_tol ) if ( me % verbose ) write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        alpha_min = ' , alpha_min x = xold + p * alpha_min if ( all ( x == xnew )) then ! already computed in the func else call me % func ( x , fvec ) f = norm2 ( fvec ) end if contains real ( wp ) function func_for_fmin ( alpha ) !! function for [[fmin]] implicit none real ( wp ), intent ( in ) :: alpha !! indep variable xnew = xold + p * alpha call me % func ( xnew , fvec ) func_for_fmin = norm2 ( fvec ) ! return result f = func_for_fmin ! just in case this is the solution end function func_for_fmin end subroutine exact_linesearch","tags":"","loc":"proc/exact_linesearch.html"},{"title":"fixed_point_linesearch – nlesolver-fortran","text":"private  subroutine fixed_point_linesearch(me, xold, p, x, f, fvec, fjac, fjac_sparse) A simple search that just evaluates the function at a specified\nnumber of points and picks the one with the minimum function value. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] Source Code subroutine fixed_point_linesearch ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] integer :: i !! counter integer :: n_points !! number of points to compute real ( wp ), dimension (:), allocatable :: alphas_to_try !! set of `alpha` values to try real ( wp ), dimension (:), allocatable :: x_tmp !! temp `x` real ( wp ), dimension (:), allocatable :: fvec_tmp !! temp `fvec` real ( wp ) :: f_tmp !! temp `f` real ( wp ) :: step_size !! step size for `alpha` integer :: n !! number of steps to divide the interval ! 1 o-----------o ! 2 o-----o-----o ! 3 o---o---o---o n = me % n_intervals n_points = n + 1 allocate ( alphas_to_try ( n_points )) allocate ( x_tmp ( me % n )) allocate ( fvec_tmp ( me % m )) step_size = ( me % alpha_max - me % alpha_min ) / real ( n , wp ) ! compute the alphas: alphas_to_try ( 1 ) = me % alpha_min do i = 2 , n alphas_to_try ( i ) = alphas_to_try ( i - 1 ) + step_size end do alphas_to_try ( n_points ) = me % alpha_max ! now compute the functions at these alphas: f = big do i = 1 , n_points x_tmp = xold + p * alphas_to_try ( i ) ! evaluate the function at tthis point: call me % func ( x_tmp , fvec_tmp ) f_tmp = norm2 ( fvec_tmp ) if ( f_tmp <= f ) then ! new best point x = x_tmp f = f_tmp fvec = fvec_tmp end if end do end subroutine fixed_point_linesearch","tags":"","loc":"proc/fixed_point_linesearch.html"},{"title":"nlesolver_module – nlesolver-fortran","text":"A basic multidimensional nonlinear equation solver, using a Newton-Raphson type direct method. Features Works with square, under-determined, or over-determined systems. Uses LAPACK routines ( dgesv or dgels ) to solve the linear system. Has a Broyden update option. Has various line search options. References https://en.wikipedia.org/wiki/Backtracking_line_search http://projecteuclid.org/download/pdf_1/euclid.pjm/1102995080 http://help.agi.com/stk/index.htm#gator/eq-diffcorr.htm http://gmat.sourceforge.net/doc/R2015a/html/DifferentialCorrector.html Author Jacob Williams License BSD-3 Todo add an istat output to func and grad, for user stopping\n      or to take a smaller stop (if istat>0 take a smaller step, if istat<0 abort) Note The default real kind ( wp ) can be\n      changed using optional preprocessor flags.\n      This library was built with real kind: real(kind=real64) [8 bytes] Uses fmin_module lusol_ez_module iso_fortran_env lsqr_module module~~nlesolver_module~~UsesGraph module~nlesolver_module nlesolver_module fmin_module fmin_module module~nlesolver_module->fmin_module iso_fortran_env iso_fortran_env module~nlesolver_module->iso_fortran_env lsqr_module lsqr_module module~nlesolver_module->lsqr_module lusol_ez_module lusol_ez_module module~nlesolver_module->lusol_ez_module Help Graph Key Nodes of different colours represent the following: Graph Key Module Module Submodule Submodule Subroutine Subroutine Function Function Program Program This Page's Entity This Page's Entity Solid arrows point from a submodule to the (sub)module which it is\ndescended from. Dashed arrows point from a module or program unit to \nmodules which it uses. Variables Type Visibility Attributes Name Initial integer, public, parameter :: nlesolver_rk = real64 real kind used by this module [8 bytes] integer, private, parameter :: wp = nlesolver_rk local copy of nlesolver_rk with a shorter name real(kind=wp), private, parameter :: zero = 0.0_wp real(kind=wp), private, parameter :: one = 1.0_wp real(kind=wp), private, parameter :: two = 2.0_wp real(kind=wp), private, parameter :: eps = epsilon(one) machine real(kind=wp), private, parameter :: big = huge(one) Abstract Interfaces abstract interface private  subroutine func_func(me, x, f) compute the function Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(out), dimension(:) :: f abstract interface private  subroutine grad_func(me, x, g) compute the gradient of the function (Jacobian). Dense version. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(out), dimension(:,:) :: g abstract interface private  subroutine grad_func_sparse(me, x, g) compute the gradient of the function (Jacobian). Sparse version. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(out), dimension(:) :: g sparse jacobian. length is n_nonzeros abstract interface private  subroutine export_func(me, x, f, iter) export an iteration: Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(:) :: x real(kind=wp), intent(in), dimension(:) :: f integer, intent(in) :: iter iteration number abstract interface private  subroutine wait_func(me, user_stop) enable a user-triggered stop of the iterations: Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me logical, intent(out) :: user_stop abstract interface private  subroutine linesearch_func(me, xold, p, x, f, fvec, fjac, fjac_sparse) line search method. Note that not all inputs/outputs are\nused by all methods. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f input: current magnitude of fvec , output: new value of f real(kind=wp), intent(inout), dimension(me%m) :: fvec input: current function vector, output: new function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] Derived Types type, public :: nlesolver_type Nonlinear equations solver class. Components Type Visibility Attributes Name Initial integer, private :: n = 0 number of opt vars integer, private :: m = 0 number of constraints integer, private :: max_iter = 100 maximum number of iterations real(kind=wp), private :: tol = 1.0e-6_wp convergence tolerance for function values real(kind=wp), private :: alpha = 1.0_wp step length (when specified constant) real(kind=wp), private :: alpha_min = 0.1_wp minimum step length (when allowed to vary) real(kind=wp), private :: alpha_max = 1.0_wp maximum step length (when allowed to vary) real(kind=wp), private :: tolx = 1.0e-8_wp convergence tolerance for x real(kind=wp), private :: c = 0.5_wp backtracking linesearch parameter (0,1) real(kind=wp), private :: tau = 0.5_wp backtracking linesearch parameter (0,1) real(kind=wp), private :: fmin_tol = 1.0e-5_wp tolerance for \"exact\" linesearch integer, private :: n_intervals = 2 number of intervals for fixed point linesearch logical, private :: use_broyden = .false. if true, a Broyden update is used\nrather than computing the Jacobian\nat every step. The grad function is\nonly called for the initial evaluation. integer, private :: broyden_update_n = 4 if this value is >0 , the Broyden update\nis computed at most this many times before\nthe full Jacobian is recomputed. integer, private :: n_uphill_max = 5 maximum number of consecutive steps\nto allow where the value of f increases logical, private :: verbose = .false. verbose output printing integer, private :: iunit = output_unit output unit for printing (assumed to be open). character(len=:), private, allocatable :: message latest status message integer, private :: istat = -999 latest status message procedure( func_func ), private, pointer :: func => null() user-supplied routine to compute the function procedure( export_func ), private, pointer :: export_iteration => null() user-supplied routine to export iterations procedure( wait_func ), private, pointer :: user_input_check => null() user-supplied routine to enable user to stop iterations procedure( linesearch_func ), private, pointer :: linesearch => null() line search method (determined by step_mode user input in initialize ) integer, private :: sparsity_mode = 1 sparsity mode: Read more… integer, private :: n_nonzeros = -1 number of nonzero Jacobian elements (used for sparsity_mode > 1 ) integer, private, dimension(:), allocatable :: irow sparsity pattern nonzero elements row indices. integer, private, dimension(:), allocatable :: icol sparsity pattern nonzero elements column indices real(kind=wp), private :: atol = zero relative error in definition of A real(kind=wp), private :: btol = zero relative error in definition of b real(kind=wp), private :: conlim = zero An upper limit on cond(Abar) , the apparent\ncondition number of the matrix Abar . integer, private :: itnlim = 100 max iterations integer, private :: nout = 0 output unit for printing real(kind=wp), private :: damp = zero damp parameter for LSQR integer, private :: lusol_method = 0 Read more… procedure( grad_func ), private, pointer :: grad => null() user-supplied routine to compute the gradient of the function (dense version) procedure( grad_func_sparse ), private, pointer :: grad_sparse => null() user-supplied routine to compute the gradient of the function (sparse version) Type-Bound Procedures procedure, public :: initialize => initialize_nlesolver_variables procedure, public :: solve => nlesolver_solver procedure, public :: destroy => destroy_nlesolver_variables procedure, public :: status => get_status procedure, private :: set_status Subroutines private  subroutine set_status (me, istat, string, i, r) Set status flag and message. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(in) :: istat status code character(len=*), intent(in) :: string status message integer, intent(in), optional :: i an integer value to append real(kind=wp), intent(in), optional :: r a real value to append private  subroutine get_status (me, istat, message) Return the status code and message from the nlesolver_type class. Read more… Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(out), optional :: istat Integer status code. character(len=:), intent(out), optional, allocatable :: message Text status message private  subroutine initialize_nlesolver_variables (me, n, m, max_iter, tol, alpha, alpha_min, alpha_max, tolx, fmin_tol, backtrack_c, backtrack_tau, use_broyden, broyden_update_n, step_mode, func, grad, grad_sparse, export_iteration, user_input_check, verbose, iunit, n_uphill_max, n_intervals, sparsity_mode, irow, icol, atol, btol, conlim, damp, itnlim, nout, lusol_method) Constructor for the class. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me integer, intent(in) :: n number of optimization variables integer, intent(in) :: m number of constraints integer, intent(in) :: max_iter maximum number of iterations real(kind=wp), intent(in) :: tol function convergence tolerance real(kind=wp), intent(in), optional :: alpha constant step length for step_mode=1 (0,1] real(kind=wp), intent(in), optional :: alpha_min minimum step length (0,1] real(kind=wp), intent(in), optional :: alpha_max maximum step length (0,1] real(kind=wp), intent(in), optional :: tolx convergence tolerance for changes in x real(kind=wp), intent(in), optional :: fmin_tol convergence tolerance for fmin (used when step_mode=3 ) real(kind=wp), intent(in), optional :: backtrack_c backtracking linesearch parameter (0,1) real(kind=wp), intent(in), optional :: backtrack_tau backtracking linesearch parameter (0,1) logical, intent(in), optional :: use_broyden use a Broyden update (default is False) integer, intent(in), optional :: broyden_update_n For Broyden mode, update the full Jacobian\nat most every this many iterations (must be >1)\nIf <=1 then Jacobian is only computed on the\nfirst iteration. integer, intent(in), optional :: step_mode step mode: Read more… procedure( func_func ) :: func computes the function vector procedure( grad_func ), optional :: grad computes the jacobian [required for dense mode: sparsity_mode=1 ] procedure( grad_func_sparse ), optional :: grad_sparse computes the jacobian [required for sparse mode: sparsity_mode>1 ] procedure( export_func ), optional :: export_iteration function to export each iteration procedure( wait_func ), optional :: user_input_check check for user input (to stop solver if necessary) logical, intent(in), optional :: verbose for verbose status printing integer, intent(in), optional :: iunit unit for verbose printing (assumed to be open).\nby default this is output_unit . integer, intent(in), optional :: n_uphill_max maximum number of consecutive steps\nto allow where the value of f increases integer, intent(in), optional :: n_intervals number of intervals for fixed point linesearch integer, intent(in), optional :: sparsity_mode sparsity mode: Read more… integer, intent(in), optional, dimension(:) :: irow sparsity pattern nonzero elements row indices.\nmust be specified with icol and be the same length ( n_nonzeros ). integer, intent(in), optional, dimension(:) :: icol sparsity pattern nonzero elements column indices\nmust be specified with icol and be the same length ( n_nonzeros ). real(kind=wp), intent(in), optional :: atol LSQR : relative error in definition of A real(kind=wp), intent(in), optional :: btol LSQR : relative error in definition of b real(kind=wp), intent(in), optional :: conlim LSQR : An upper limit on cond(Abar) , the apparent\ncondition number of the matrix Abar . real(kind=wp), intent(in), optional :: damp LSQR : damp factor integer, intent(in), optional :: itnlim LSQR : max iterations integer, intent(in), optional :: nout LSQR : output unit for printing integer, intent(in), optional :: lusol_method LUSOL method: Read more… private  subroutine nlesolver_solver (me, x) Main solver. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(inout), dimension(:) :: x private  subroutine destroy_nlesolver_variables (me) Destructor Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(out) :: me private  subroutine linear_solver (m, n, a, b, x, info) Solve the linear system: , using a dense, direct method. Read more… Arguments Type Intent Optional Attributes Name integer, intent(in) :: m number of rows in a integer, intent(in) :: n number of columns in a real(kind=wp), intent(in), dimension(m,n) :: a A matrix of the linear system real(kind=wp), intent(in), dimension(m) :: b RHS of the linear system real(kind=wp), intent(out), dimension(n) :: x the solution of the linear system. integer, intent(out) :: info output status flag ( =0 if success) private  subroutine simple_step (me, xold, p, x, f, fvec, fjac, fjac_sparse) Take a simple step in the search direction of p * alpha . Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] private  subroutine backtracking_linesearch (me, xold, p, x, f, fvec, fjac, fjac_sparse) Backtracking line search. Read more… Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] private  subroutine exact_linesearch (me, xold, p, x, f, fvec, fjac, fjac_sparse) An exact linesearch that uses a derivative-free minimizer to\nfind the minimum value of f(x) between x = xold + p * alpha_min and x = xold + p * alpha_max . Read more… Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse] private  subroutine fixed_point_linesearch (me, xold, p, x, f, fvec, fjac, fjac_sparse) A simple search that just evaluates the function at a specified\nnumber of points and picks the one with the minimum function value. Arguments Type Intent Optional Attributes Name class( nlesolver_type ), intent(inout) :: me real(kind=wp), intent(in), dimension(me%n) :: xold previous value of x real(kind=wp), intent(in), dimension(me%n) :: p search direction real(kind=wp), intent(out), dimension(me%n) :: x new x real(kind=wp), intent(inout) :: f magnitude of fvec real(kind=wp), intent(inout), dimension(me%m) :: fvec function vector real(kind=wp), intent(in), optional, dimension(:,:) :: fjac jacobian matrix [dense] real(kind=wp), intent(in), optional, dimension(:) :: fjac_sparse jacobian matrix [sparse]","tags":"","loc":"module/nlesolver_module.html"},{"title":"nlesolver_module.F90 – nlesolver-fortran","text":"Source Code !****************************************************************************************************** !> !  A basic multidimensional nonlinear equation solver, using a Newton-Raphson type direct method. ! !### Features !  * Works with square, under-determined, or over-determined systems. !  * Uses LAPACK routines (`dgesv` or `dgels`) to solve the linear system. !  * Has a Broyden update option. !  * Has various line search options. ! !### References !  * https://en.wikipedia.org/wiki/Backtracking_line_search !  * http://projecteuclid.org/download/pdf_1/euclid.pjm/1102995080 !  * http://help.agi.com/stk/index.htm#gator/eq-diffcorr.htm !  * http://gmat.sourceforge.net/doc/R2015a/html/DifferentialCorrector.html ! !### Author !  * Jacob Williams ! !### License !  * BSD-3 ! !@todo add an `istat` output to func and grad, for user stopping !      or to take a smaller stop (if istat>0 take a smaller step, if istat<0 abort) ! !@note The default real kind (`wp`) can be !      changed using optional preprocessor flags. !      This library was built with real kind: #ifdef REAL32 !      `real(kind=real32)` [4 bytes] #elif REAL64 !      `real(kind=real64)` [8 bytes] #elif REAL128 !      `real(kind=real128)` [16 bytes] #else !      `real(kind=real64)` [8 bytes] #endif module nlesolver_module use iso_fortran_env use fmin_module , only : fmin use lsqr_module , only : lsqr_solver_ez use lusol_ez_module , only : solve , lusol_settings implicit none private #ifdef REAL32 integer , parameter , public :: nlesolver_rk = real32 !! real kind used by this module [4 bytes] #elif REAL64 integer , parameter , public :: nlesolver_rk = real64 !! real kind used by this module [8 bytes] #elif REAL128 integer , parameter , public :: nlesolver_rk = real128 !! real kind used by this module [16 bytes] #else integer , parameter , public :: nlesolver_rk = real64 !! real kind used by this module [8 bytes] #endif integer , parameter :: wp = nlesolver_rk !! local copy of `nlesolver_rk` with a shorter name real ( wp ), parameter :: zero = 0.0_wp real ( wp ), parameter :: one = 1.0_wp real ( wp ), parameter :: two = 2.0_wp real ( wp ), parameter :: eps = epsilon ( one ) !! machine  \\epsilon  real ( wp ), parameter :: big = huge ( one ) !********************************************************* type , public :: nlesolver_type !! Nonlinear equations solver class. private integer :: n = 0 !! number of opt vars integer :: m = 0 !! number of constraints integer :: max_iter = 100 !! maximum number of iterations real ( wp ) :: tol = 1.0e-6_wp !! convergence tolerance for function values real ( wp ) :: alpha = 1.0_wp !! step length (when specified constant) real ( wp ) :: alpha_min = 0.1_wp !! minimum step length (when allowed to vary) real ( wp ) :: alpha_max = 1.0_wp !! maximum step length (when allowed to vary) real ( wp ) :: tolx = 1.0e-8_wp !! convergence tolerance for `x` real ( wp ) :: c = 0.5_wp !! backtracking linesearch parameter (0,1) real ( wp ) :: tau = 0.5_wp !! backtracking linesearch parameter (0,1) real ( wp ) :: fmin_tol = 1.0e-5_wp !! tolerance for \"exact\" linesearch integer :: n_intervals = 2 !! number of intervals for fixed point linesearch logical :: use_broyden = . false . !! if true, a Broyden update is used !! rather than computing the Jacobian !! at every step. The `grad` function is !! only called for the initial evaluation. integer :: broyden_update_n = 4 !! if this value is `>0`, the Broyden update !! is computed at most this many times before !! the full Jacobian is recomputed. integer :: n_uphill_max = 5 !! maximum number of consecutive steps !! to allow where the value of `f` increases logical :: verbose = . false . !! verbose output printing integer :: iunit = output_unit !! output unit for printing (assumed to be open). character ( len = :), allocatable :: message !! latest status message integer :: istat = - 999 !! latest status message procedure ( func_func ), pointer :: func => null () !! user-supplied routine to compute the function procedure ( export_func ), pointer :: export_iteration => null () !! user-supplied routine to export iterations procedure ( wait_func ), pointer :: user_input_check => null () !! user-supplied routine to enable user to stop iterations procedure ( linesearch_func ), pointer :: linesearch => null () !! line search method (determined by `step_mode` user input in [[nlesolver_type:initialize]]) ! sparsity options: integer :: sparsity_mode = 1 !! sparsity mode: !! !! * 1 - assume dense (use dense solver) !! * 2 - assume sparse (use LSQR sparse solver). !! * 3 - assume sparse (use LUSOL sparse solver). integer :: n_nonzeros = - 1 !! number of nonzero Jacobian elements (used for `sparsity_mode > 1`) integer , dimension (:), allocatable :: irow !! sparsity pattern nonzero elements row indices. integer , dimension (:), allocatable :: icol !! sparsity pattern nonzero elements column indices ! LSQR parameters: real ( wp ) :: atol = zero !! relative error in definition of `A` real ( wp ) :: btol = zero !! relative error in definition of `b` real ( wp ) :: conlim = zero !! An upper limit on `cond(Abar)`, the apparent !! condition number of the matrix `Abar`. integer :: itnlim = 100 !! max iterations integer :: nout = 0 !! output unit for printing real ( wp ) :: damp = zero !! damp parameter for LSQR ! LUSOL parameters: integer :: lusol_method = 0 !! * 0 => TPP: Threshold Partial   Pivoting. !! * 1 => TRP: Threshold Rook      Pivoting. !! * 2 => TCP: Threshold Complete  Pivoting. ! dense version: procedure ( grad_func ), pointer :: grad => null () !! user-supplied routine to compute the gradient of the function (dense version) ! sparse version: procedure ( grad_func_sparse ), pointer :: grad_sparse => null () !! user-supplied routine to compute the gradient of the function (sparse version) contains private procedure , public :: initialize => initialize_nlesolver_variables procedure , public :: solve => nlesolver_solver procedure , public :: destroy => destroy_nlesolver_variables procedure , public :: status => get_status procedure :: set_status end type nlesolver_type !********************************************************* abstract interface subroutine func_func ( me , x , f ) !! compute the function import :: wp , nlesolver_type implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension (:), intent ( in ) :: x real ( wp ), dimension (:), intent ( out ) :: f end subroutine func_func subroutine grad_func ( me , x , g ) !! compute the gradient of the function (Jacobian). Dense version. import :: wp , nlesolver_type implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension (:), intent ( in ) :: x real ( wp ), dimension (:,:), intent ( out ) :: g end subroutine grad_func subroutine grad_func_sparse ( me , x , g ) !! compute the gradient of the function (Jacobian). Sparse version. import :: wp , nlesolver_type implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension (:), intent ( in ) :: x real ( wp ), dimension (:), intent ( out ) :: g !! sparse jacobian. length is `n_nonzeros` end subroutine grad_func_sparse subroutine export_func ( me , x , f , iter ) !! export an iteration: import :: wp , nlesolver_type implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension (:), intent ( in ) :: x real ( wp ), dimension (:), intent ( in ) :: f integer , intent ( in ) :: iter !! iteration number end subroutine export_func subroutine wait_func ( me , user_stop ) !! enable a user-triggered stop of the iterations: import :: wp , nlesolver_type implicit none class ( nlesolver_type ), intent ( inout ) :: me logical , intent ( out ) :: user_stop end subroutine wait_func subroutine linesearch_func ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) !! line search method. Note that not all inputs/outputs are !! used by all methods. import :: wp , nlesolver_type implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! * input: current magnitude of `fvec`, !! * output: new value of `f` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! * input: current function vector, !! * output: new function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] end subroutine linesearch_func end interface contains !******************************************************************************************************* !***************************************************************************************** !> !  Set status flag and message. subroutine set_status ( me , istat , string , i , r ) implicit none class ( nlesolver_type ), intent ( inout ) :: me integer , intent ( in ) :: istat !! status code character ( len =* ), intent ( in ) :: string !! status message integer , intent ( in ), optional :: i !! an integer value to append real ( wp ), intent ( in ), optional :: r !! a real value to append character ( len = 256 ) :: numstr !! for number fo string conversion character ( len = :), allocatable :: message !! the full message to log integer :: iostat !! write `iostat` code message = trim ( string ) if ( present ( i )) then numstr = '' write ( numstr , fmt =* , iostat = iostat ) i if ( iostat /= 0 ) numstr = '****' message = message // ' ' // trim ( adjustl ( numstr )) end if if ( present ( r )) then numstr = '' write ( numstr , fmt =* , iostat = iostat ) r if ( iostat /= 0 ) numstr = '****' message = message // ' ' // trim ( adjustl ( numstr )) end if if ( me % verbose ) then write ( me % iunit , '(A)' , iostat = iostat ) message end if ! store in the class: me % istat = istat me % message = message end subroutine set_status !***************************************************************************************** !***************************************************************************************** !> !  Return the status code and message from the [[nlesolver_type]] class. ! !### Status codes ! !  * -1   -- Error: Invalid alpha !  * -2   -- Error: Invalid alpha_min !  * -3   -- Error: Invalid alpha_max !  * -4   -- Error: Alpha_min must be < alpha_max !  * -5   -- Error: Invalid step_mode !  * -6   -- Error solving linear system !  * -7   -- Error: More than 5 steps in the uphill direction !  * -8   -- Error: Divide by zero when computing Broyden update !  * -9   -- Error: Out of memory !  * -10  -- Error: function routine is not associated !  * -11  -- Error: gradient routine is not associated !  * -12  -- Error: backtracking linesearch c must be in range (0, 1) !  * -13  -- Error: backtracking linesearch tau must be in range (0, 1) !  * -14  -- Error: must specify grad_sparse, irow, and icol for sparsity_mode > 1 !  * -15  -- Error: irow and icol must be the same length !  * -999 -- Error: class has not been initialized !  * 0    -- Class successfully initialized in [[nlesolver_type:initialize]] !  * 1    -- Required accuracy achieved !  * 2    -- Solution cannot be improved !  * 3    -- Maximum number of iterations reached !  * 4    -- Stopped by the user subroutine get_status ( me , istat , message ) implicit none class ( nlesolver_type ), intent ( inout ) :: me integer , intent ( out ), optional :: istat !! Integer status code. character ( len = :), allocatable , intent ( out ), optional :: message !! Text status message if ( present ( istat )) istat = me % istat if ( present ( message )) then if ( allocated ( me % message )) then message = trim ( me % message ) else message = 'Error: class has not been initialized' end if end if end subroutine get_status !***************************************************************************************** !***************************************************************************************** !> !  Constructor for the class. subroutine initialize_nlesolver_variables ( me ,& n , m , max_iter , tol , alpha , alpha_min , alpha_max , tolx , fmin_tol ,& backtrack_c , backtrack_tau ,& use_broyden , broyden_update_n , step_mode ,& func , grad , grad_sparse ,& export_iteration , user_input_check ,& verbose , iunit , n_uphill_max , n_intervals ,& sparsity_mode , irow , icol ,& atol , btol , conlim , damp , itnlim , nout ,& lusol_method ) implicit none class ( nlesolver_type ), intent ( inout ) :: me integer , intent ( in ) :: n !! number of optimization variables integer , intent ( in ) :: m !! number of constraints integer , intent ( in ) :: max_iter !! maximum number of iterations real ( wp ), intent ( in ) :: tol !! function convergence tolerance procedure ( func_func ) :: func !! computes the function vector procedure ( grad_func ), optional :: grad !! computes the jacobian [required for dense mode: `sparsity_mode=1`] procedure ( grad_func_sparse ), optional :: grad_sparse !! computes the jacobian [required for sparse mode: `sparsity_mode>1`] integer , intent ( in ), optional :: step_mode !! step mode: !! !!  * 1 = use the specified `alpha` (0,1] !!  * 2 = backtracking linesearch (between `alpha_min` and `alpha_max`) !!  * 3 = exact linesearch (between `alpha_min` and `alpha_max`) !!  * 4 = evaluate function at specified fixed points  (between `alpha_min` and `alpha_max`) real ( wp ), intent ( in ), optional :: alpha !! constant step length for `step_mode=1` (0,1] real ( wp ), intent ( in ), optional :: alpha_min !! minimum step length (0,1] real ( wp ), intent ( in ), optional :: alpha_max !! maximum step length (0,1] real ( wp ), intent ( in ), optional :: tolx !! convergence tolerance for changes in `x` real ( wp ), intent ( in ), optional :: fmin_tol !! convergence tolerance for [[fmin]] (used when `step_mode=3`) real ( wp ), intent ( in ), optional :: backtrack_c !! backtracking linesearch parameter (0,1) real ( wp ), intent ( in ), optional :: backtrack_tau !! backtracking linesearch parameter (0,1) logical , intent ( in ), optional :: use_broyden !! use a Broyden update (default is False) integer , intent ( in ), optional :: broyden_update_n !! For Broyden mode, update the full Jacobian !! at most every this many iterations (must be >1) !! If <=1 then Jacobian is only computed on the !! first iteration. procedure ( export_func ), optional :: export_iteration !! function to export each iteration procedure ( wait_func ), optional :: user_input_check !! check for user input (to stop solver if necessary) logical , intent ( in ), optional :: verbose !! for verbose status printing integer , intent ( in ), optional :: iunit !! unit for verbose printing (assumed to be open). !! by default this is `output_unit`. integer , intent ( in ), optional :: n_uphill_max !! maximum number of consecutive steps !! to allow where the value of `f` increases integer , intent ( in ), optional :: n_intervals !! number of intervals for fixed point linesearch integer , intent ( in ), optional :: sparsity_mode !! sparsity mode: !! !! * 1 - assume dense (use dense solver) !!   Must specify `grad` for this mode. !! * 2 - assume sparse (use LSQR sparse solver). !! * 3 - assume sparse (use LUSOL sparse solver). !! Must also specify `grad_sparse` and the `irow` and `icol` !! sparsity pattern for `mode>1`. integer , dimension (:), intent ( in ), optional :: irow !! sparsity pattern nonzero elements row indices. !! must be specified with `icol` and be the same length (`n_nonzeros`). integer , dimension (:), intent ( in ), optional :: icol !! sparsity pattern nonzero elements column indices !! must be specified with `icol` and be the same length (`n_nonzeros`). real ( wp ), intent ( in ), optional :: atol !! `LSQR`: relative error in definition of `A` real ( wp ), intent ( in ), optional :: btol !! `LSQR`: relative error in definition of `b` real ( wp ), intent ( in ), optional :: conlim !! `LSQR`: An upper limit on `cond(Abar)`, the apparent !! condition number of the matrix `Abar`. real ( wp ), intent ( in ), optional :: damp !! `LSQR`: damp factor integer , intent ( in ), optional :: itnlim !! `LSQR`: max iterations integer , intent ( in ), optional :: nout !! `LSQR`: output unit for printing integer , intent ( in ), optional :: lusol_method !! `LUSOL` method: !! !! * 0 => TPP: Threshold Partial   Pivoting. !! * 1 => TRP: Threshold Rook      Pivoting. !! * 2 => TCP: Threshold Complete  Pivoting. logical :: status_ok !! true if there were no errors status_ok = . true . !required: me % n = abs ( n ) me % m = abs ( m ) me % max_iter = abs ( max_iter ) me % tol = abs ( tol ) me % func => func if ( present ( grad )) me % grad => grad if ( present ( grad_sparse )) me % grad_sparse => grad_sparse !optional: if ( present ( step_mode )) then select case ( step_mode ) case ( 1 ) ! = use the specified `alpha` (0,1] me % linesearch => simple_step case ( 2 ) ! = backtracking linesearch (between `alpha_min` and `alpha_max`) me % linesearch => backtracking_linesearch case ( 3 ) ! = exact linesearch (between `alpha_min` and `alpha_max`) me % linesearch => exact_linesearch case ( 4 ) ! = evaluate function at specified fixed points (between `alpha_min` and `alpha_max`) me % linesearch => fixed_point_linesearch case default status_ok = . false . call me % set_status ( istat = - 5 , string = 'Error: invalid step_mode:' , i = step_mode ) return end select else me % linesearch => simple_step end if if ( present ( alpha )) me % alpha = abs ( alpha ) if ( present ( alpha_min )) me % alpha_min = abs ( alpha_min ) if ( present ( alpha_max )) me % alpha_max = abs ( alpha_max ) if ( present ( tolx )) me % tolx = abs ( tolx ) if ( present ( backtrack_c )) me % c = abs ( backtrack_c ) if ( present ( backtrack_tau )) me % tau = abs ( backtrack_tau ) if ( present ( use_broyden )) me % use_broyden = use_broyden if ( present ( broyden_update_n )) me % broyden_update_n = abs ( broyden_update_n ) if ( present ( verbose )) me % verbose = verbose if ( present ( iunit )) me % iunit = iunit if ( present ( n_uphill_max )) me % n_uphill_max = abs ( n_uphill_max ) if ( present ( n_intervals )) me % n_intervals = max ( abs ( n_intervals ), 1 ) if ( present ( fmin_tol )) me % fmin_tol = abs ( fmin_tol ) if ( present ( export_iteration )) me % export_iteration => export_iteration if ( present ( user_input_check )) me % user_input_check => user_input_check ! error checks: if ( me % alpha < zero . or . me % alpha > one ) then status_ok = . false . call me % set_status ( istat = - 1 , string = 'Error: invalid alpha:' , r = me % alpha ) return end if if ( me % alpha_min < zero . or . me % alpha_min > one ) then status_ok = . false . call me % set_status ( istat = - 2 , string = 'Error: invalid alpha_min:' , r = me % alpha_min ) return end if if ( me % alpha_max < zero . or . me % alpha_max > one ) then status_ok = . false . call me % set_status ( istat = - 3 , string = 'Error: invalid alpha_max:' , r = me % alpha_max ) return end if if ( me % alpha_max <= me % alpha_min ) then status_ok = . false . call me % set_status ( istat = - 4 , string = 'Error: alpha_min must be < alpha_max' ) return end if if ( me % c < zero . or . me % c > one ) then status_ok = . false . call me % set_status ( istat = - 12 , string = 'Error: backtracking linesearch c must be in range (0, 1):' , r = me % c ) return end if if ( me % tau < zero . or . me % tau > one ) then status_ok = . false . call me % set_status ( istat = - 13 , string = 'Error: backtracking linesearch tau must be in range (0, 1):' , r = me % tau ) return end if ! initialize: me % n_nonzeros = - 1 ! not used if ( allocated ( me % irow )) deallocate ( me % irow ) if ( allocated ( me % icol )) deallocate ( me % icol ) if ( present ( sparsity_mode )) then me % sparsity_mode = sparsity_mode if ( sparsity_mode > 1 ) then ! sparse solver method if ( present ( irow ) . and . present ( icol ) . and . present ( grad_sparse )) then if ( size ( irow ) == size ( icol )) then me % n_nonzeros = size ( irow ) me % irow = irow me % icol = icol else call me % set_status ( istat = - 15 , string = 'Error: irow and icol must be the same length' ) return end if else call me % set_status ( istat = - 14 , string = 'Error: must specify grad_sparse, irow, and icol for sparsity_mode > 1' ) return end if ! LSQR optional inputs: if ( present ( atol )) me % atol = atol if ( present ( btol )) me % btol = btol if ( present ( conlim )) me % conlim = conlim if ( present ( damp )) me % damp = damp if ( present ( itnlim )) me % itnlim = itnlim if ( present ( nout )) me % nout = nout ! LUSOL method if ( present ( nout )) me % lusol_method = lusol_method end if end if if ( status_ok ) then call me % set_status ( istat = 0 , string = 'Class successfully initialized' ) end if end subroutine initialize_nlesolver_variables !***************************************************************************************** !***************************************************************************************** !> !  Main solver. subroutine nlesolver_solver ( me , x ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension (:), intent ( inout ) :: x real ( wp ), dimension (:) , allocatable :: fvec !! function vector real ( wp ), dimension (:,:), allocatable :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), allocatable :: fjac_sparse !! jacobian matrix [sparse] real ( wp ), dimension (:), allocatable :: prev_fjac_sparse !! previous jacobian matrix [sparse] real ( wp ), dimension (:) , allocatable :: rhs !! linear system right-hand side real ( wp ), dimension (:) , allocatable :: p !! search direction real ( wp ), dimension (:) , allocatable :: xold !! previous value of `x` real ( wp ), dimension (:) , allocatable :: prev_fvec !! previous function vector real ( wp ), dimension (:,:), allocatable :: prev_fjac !! previous jacobian matrix real ( wp ), dimension (:,:), allocatable :: delf !! used for Broyden (rank 2 for `matmul`) real ( wp ), dimension (:,:), allocatable :: delx !! used for Broyden (rank 2 for `matmul`) logical :: user_stop !! user stop button flag integer :: info !! status flag from the [[linear_solver]] integer :: iter !! iteration counter real ( wp ) :: f !! magnitude of `fvec` real ( wp ) :: fold !! previous value of `f` integer :: n_uphill !! number of steps taken in the \"uphill\" direction !! (where `f` is increasing) real ( wp ) :: delxmag2 !! used for Broyden logical :: recompute_jac !! if using Broyden, and we want to call the user !! jacobian routine instead integer :: broyden_counter !! number of times the broyden update has been used integer :: alloc_stat !! allocation status flag type ( lsqr_solver_ez ) :: sparse_solver !! sparse LSQR solver class type ( lusol_settings ) :: lusol_options integer :: i !! counter integer , dimension (:), allocatable :: idx , index_array !! for sparse indexing character ( len = 10 ) :: i_str !! string version of `i` for row string if ( me % istat < 0 ) return ! class was not initialized properly if (. not . associated ( me % func )) then call me % set_status ( istat = - 10 , string = 'Error: function routine is not associated' ) return end if if ( me % sparsity_mode == 1 . and . . not . associated ( me % grad )) then call me % set_status ( istat = - 11 , string = 'Error: gradient routine is not associated' ) return end if if ( me % sparsity_mode > 1 . and . . not . associated ( me % grad_sparse )) then call me % set_status ( istat = - 11 , string = 'Error: gradient routine is not associated' ) return end if ! initialize: iter = 0 n_uphill = 0 recompute_jac = . false . broyden_counter = 0 ! allocate the arrays: alloc_stat = 0 if ( alloc_stat == 0 ) allocate ( fvec ( me % m ) , stat = alloc_stat ) if ( me % sparsity_mode == 1 ) then ! dense if ( alloc_stat == 0 ) allocate ( fjac ( me % m , me % n ) , stat = alloc_stat ) else ! sparse if ( alloc_stat == 0 ) allocate ( fjac_sparse ( me % n_nonzeros ) , stat = alloc_stat ) if ( me % use_broyden . and . alloc_stat == 0 ) allocate ( prev_fjac_sparse ( me % n_nonzeros ) , stat = alloc_stat ) end if if ( alloc_stat == 0 ) allocate ( rhs ( me % m ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( p ( me % n ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( xold ( me % n ) , stat = alloc_stat ) if ( me % use_broyden ) then ! only need these for broyden: if ( alloc_stat == 0 ) allocate ( prev_fvec ( me % m ) , stat = alloc_stat ) if ( me % sparsity_mode /= 1 . and . alloc_stat == 0 ) then allocate ( prev_fjac ( me % m , me % n ) , stat = alloc_stat ) index_array = [( i , i = 1 , me % n_nonzeros )] ! an array to index the sparse jacobian elements end if if ( alloc_stat == 0 ) allocate ( delf ( me % m , 1 ) , stat = alloc_stat ) if ( alloc_stat == 0 ) allocate ( delx ( me % n , 1 ) , stat = alloc_stat ) end if if ( alloc_stat /= 0 ) then call me % set_status ( istat = - 9 , string = 'Error: Out of memory' ) return else me % istat = - 998 me % message = 'Unknown error' end if ! evaluate the function: call me % func ( x , fvec ) f = norm2 ( fvec ) ! check to see if initial guess is a root: if ( f <= me % tol ) then call me % set_status ( istat = 1 , string = 'Required accuracy achieved' ) else ! main iteration loop: do iter = 1 , me % max_iter ! Export the current iteration: if ( associated ( me % export_iteration )) call me % export_iteration ( x , fvec , iter ) ! Check for user stop: if ( associated ( me % user_input_check )) then call me % user_input_check ( user_stop ) if ( user_stop ) then call me % set_status ( istat = 4 , string = 'Stopped by the user' ) exit end if end if if ( me % use_broyden . and . . not . recompute_jac ) then if ( iter == 1 ) then ! always compute Jacobian on the first iteration !call me%grad(x,fjac) select case ( me % sparsity_mode ) case ( 1 ) call me % grad ( x , fjac ) case ( 2 :) call me % grad_sparse ( x , fjac_sparse ) end select broyden_counter = 0 else ! and use Broyden update to estimate Jacobian ! for subsequent iterations. ! note: fvec was computed the last iteration delx (:, 1 ) = x - xold delf (:, 1 ) = fvec - prev_fvec if ( me % sparsity_mode == 1 ) then ! dense delxmag2 = dot_product ( delx (:, 1 ), delx (:, 1 )) if ( delxmag2 < eps ) then call me % set_status ( istat = - 8 , & string = 'Error: Divide by zero when computing Broyden update' ) exit end if ! Jacobian estimate: ! This is the equation from wikipedia : https://en.wikipedia.org/wiki/Broyden%27s_method fjac = prev_fjac + matmul (( delf - matmul ( prev_fjac , delx )), transpose ( delx )) / delxmag2 ! see also: eqn 4 in Schubert, which is different ... else ! using a sparse option ! Just a row-by-row version of the fjac equation above. ! see L.K. Schubert, 1970 do i = 1 , me % m idx = pack ( index_array , mask = me % irow == i ) ! the nonzero elements in this row if ( size ( idx ) == 0 ) cycle ! no non-zeros in this row associate ( dx => delx ( me % icol ( idx ),:)) ! nonzero x vec for this row delxmag2 = dot_product ( dx (:, 1 ), dx (:, 1 )) ! only those x's for this row if ( delxmag2 < eps ) then write ( i_str , '(I10)' ) i call me % set_status ( istat = - 8 , & string = 'Error: Divide by zero when computing sparse Broyden update for row ' // & trim ( adjustl ( i_str ))) exit end if fjac_sparse ( idx ) = prev_fjac_sparse ( idx ) + & matmul (( delf ( i , 1 ) - matmul ( prev_fjac_sparse ( idx ), dx )), transpose ( dx )) / delxmag2 end associate end do end if broyden_counter = broyden_counter + 1 end if prev_fvec = fvec if ( me % sparsity_mode == 1 ) then prev_fjac = fjac else prev_fjac_sparse = fjac_sparse end if else ! compute the jacobian: select case ( me % sparsity_mode ) case ( 1 ) call me % grad ( x , fjac ) case ( 2 :) call me % grad_sparse ( x , fjac_sparse ) end select recompute_jac = . false . ! for broyden broyden_counter = 0 end if xold = x fold = f ! compute the search direction p by solving linear system: rhs = - fvec ! RHS of the linear system select case ( me % sparsity_mode ) case ( 1 ) ! use dense solver call linear_solver ( me % m , me % n , fjac , rhs , p , info ) case ( 2 ) ! initialize the LSQR sparse solver call sparse_solver % initialize ( me % m , me % n , fjac_sparse , me % irow , me % icol ,& atol = me % atol , & btol = me % btol , & conlim = me % conlim , & itnlim = me % itnlim , & nout = me % nout ) call sparse_solver % solve ( rhs , me % damp , p , info ) ! solve the linear system ! check convergence: select case ( info ) case ( 4 ) call me % set_status ( istat = - 1004 , & string = 'LSQR Error: The system appears to be ill-conditioned. istop =' , i = info ) exit case ( 5 ) call me % set_status ( istat = - 1005 , & string = 'LSQR Error: The iteration limit was reached. istop =' , i = info ) exit case default info = 0 end select case ( 3 ) ! use lusol solver lusol_options % method = me % lusol_method call solve ( me % n , me % m , me % n_nonzeros , me % irow , me % icol , fjac_sparse , rhs , p , info ,& settings = lusol_options ) end select ! check for errors: if ( info /= 0 ) then call me % set_status ( istat = - 6 , string = 'Error solving linear system. info =' , i = info ) exit else ! next step, using the specified method: call me % linesearch ( xold , p , x , f , fvec , fjac , fjac_sparse ) ! keep track of the number of steps in the \"uphill\" direction: if ( f > fold ) then n_uphill = n_uphill + 1 else n_uphill = 0 end if ! check for stopping conditions if ( f <= me % tol ) then call me % set_status ( istat = 1 , string = 'Required accuracy achieved' ) exit elseif ( maxval ( abs ( x - xold )) <= me % tolx ) then call me % set_status ( istat = 2 , string = 'Solution cannot be improved' ) exit elseif ( iter == me % max_iter ) then call me % set_status ( istat = 3 , string = 'Maximum number of iterations reached' ) exit elseif ( n_uphill > me % n_uphill_max ) then call me % set_status ( istat = 5 , string = 'Too many steps in the uphill direction' ) exit elseif ( me % use_broyden ) then ! If delxmag2 is too small when using broyden, just ! call the user-supplied jacobian function to avoid ! a divide by zero on the next step. This should ! normally only happen when the solution is almost converged. if ( norm2 ( x - xold ) ** 2 <= eps ) then recompute_jac = . true . else if ( me % broyden_update_n > 0 ) then ! Note that we also recompute if we have taken an uphill step if ( broyden_counter == me % broyden_update_n . or . n_uphill > 0 ) then ! time to recompute the full jacobian recompute_jac = . true . end if end if end if endif end if end do !end of iterations loop end if !Export the last iteration: iter = iter + 1 if ( associated ( me % export_iteration )) call me % export_iteration ( x , fvec , iter ) end subroutine nlesolver_solver !***************************************************************************************** !***************************************************************************************** !> !   Destructor subroutine destroy_nlesolver_variables ( me ) implicit none class ( nlesolver_type ), intent ( out ) :: me me % message = 'Error: class has not been initialized' me % istat = - 999 end subroutine destroy_nlesolver_variables !***************************************************************************************** !***************************************************************************************** !> !  Solve the linear system:  Ax = b , using a dense, direct method. ! !  * if `n=m` : use LAPACK `dgesv` (LU decomposition) !  * if `n/=m` : use LAPACK `dgels` (if m>n uses QR factorization, !    if m<n uses LQ factorization) subroutine linear_solver ( m , n , a , b , x , info ) implicit none integer , intent ( in ) :: n !! number of columns in `a` integer , intent ( in ) :: m !! number of rows in `a` real ( wp ), dimension ( m , n ), intent ( in ) :: a !! `A` matrix of the linear system real ( wp ), dimension ( m ), intent ( in ) :: b !! RHS of the linear system real ( wp ), dimension ( n ), intent ( out ) :: x !! the solution of the linear system. integer , intent ( out ) :: info !! output status flag (`=0` if success) ! LAPACK routine interfaces: interface subroutine dgesv ( n , nrhs , a , lda , ipiv , b , ldb , info ) !! See: [?gesv](https://www.intel.com/content/www/us/en/develop/documentation/onemkl-developer-reference-fortran/top/lapack-routines/lapack-linear-equation-routines/lapack-linear-equation-driver-routines/gesv.html) import :: wp implicit none integer :: info integer :: lda integer :: ldb integer :: n integer :: nrhs integer :: ipiv ( * ) real ( wp ) :: a ( lda , * ) real ( wp ) :: b ( ldb , * ) end subroutine dgesv subroutine dgels ( trans , m , n , nrhs , a , lda , b , ldb , work , lwork , info ) !! See: [?gels](https://www.intel.com/content/www/us/en/develop/documentation/onemkl-developer-reference-fortran/top/lapack-routines/lapack-least-squares-and-eigenvalue-problem/lapack-least-squares-eigenvalue-problem-driver/linear-least-squares-lls-problems-lapack-driver/gels.html) import :: wp implicit none character :: trans integer :: info integer :: lda integer :: ldb integer :: lwork integer :: m integer :: n integer :: nrhs real ( wp ) :: a ( lda , * ) real ( wp ) :: b ( ldb , * ) real ( wp ) :: work ( * ) end subroutine dgels end interface integer , dimension (:), allocatable :: ipiv !! pivot indices array real ( wp ), dimension (:,:), allocatable :: bmat !! copy of `b` so it won't be overwritten real ( wp ), dimension (:), allocatable :: work !! work array for `dgels` real ( wp ), dimension (:,:), allocatable :: amat !! copy of `a` so it won't be overwritten integer :: lwork !! size of `work` allocate ( amat ( m , n )) allocate ( bmat ( max ( 1 , m , n ), 1 )) if ( n == m ) then !normal inverse allocate ( ipiv ( n )) amat = a bmat ( 1 : n , 1 ) = b call dgesv ( n , 1 , amat , n , ipiv , bmat , n , info ) x = bmat ( 1 : n , 1 ) else amat = a bmat = zero bmat ( 1 : m , 1 ) = b lwork = min ( m , n ) + max ( 1 , m , n ) allocate ( work ( lwork )) call dgels ( 'N' , m , n , 1 , amat , m , bmat , max ( 1 , m , n ), work , lwork , info ) x = bmat ( 1 : n , 1 ) end if end subroutine linear_solver !***************************************************************************************** !***************************************************************************************** !> !  Take a simple step in the search direction of `p * alpha`. subroutine simple_step ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] x = xold + p * me % alpha !evaluate the function at the new point: call me % func ( x , fvec ) f = norm2 ( fvec ) end subroutine simple_step !***************************************************************************************** !***************************************************************************************** !> !  Backtracking line search. ! !### See also !  * [Backtracking line search](https://en.wikipedia.org/wiki/Backtracking_line_search) ! !@note Either `fjac` or `fjac_sparse` should be present. subroutine backtracking_linesearch ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] integer :: i !! counter real ( wp ) :: slope !! local slope of the function of `alpha` along the search direction used for line search logical :: min_alpha_reached !! if the minimum step size is reached during the line search real ( wp ) :: alpha !! `alpha` for the line search real ( wp ) :: ftmp !! `f` value for linesearch real ( wp ) :: t !! used for line search real ( wp ), dimension (:), allocatable :: gradf !! line search objective function gradient vector real ( wp ), dimension (:), allocatable :: xtmp !! `x` value for linesearch real ( wp ), dimension (:), allocatable :: fvectmp !! `fvec` value for linesearch ! allocate arrays: allocate ( gradf ( me % n )) allocate ( xtmp ( me % n )) allocate ( fvectmp ( me % m )) ! compute the gradient of the function to be minimized ! (which in this case is 1/2 the norm of fvec). Use the chain ! rule and the Jacobian matrix already computed. if ( present ( fjac )) then ! dense do i = 1 , me % n gradf ( i ) = dot_product ( fvec , fjac (:, i )) end do else ! sparse do i = 1 , me % n gradf ( i ) = dot_product ( fvec , pack ( fjac_sparse , mask = me % icol == i )) end do end if slope = dot_product ( p , gradf ) t = - me % c * slope if ( me % verbose ) then write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        slope    = ' , slope write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        t        = ' , t end if ! perform the line search: min_alpha_reached = . false . alpha = me % alpha_max ! start with the largest step do xtmp = xold + p * alpha call me % func ( xtmp , fvectmp ) ftmp = norm2 ( fvectmp ) if ( me % verbose ) then write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        alpha    = ' , alpha , ' f       = ' , ftmp if ( f - ftmp >= alpha * t ) then write ( me % iunit , '(1P,2(A,1X,E16.6),1X,A)' ) '        f - ftmp = ' , f - ftmp , ' alpha*t = ' , alpha * t , ' [ACCEPTED]' else write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        f - ftmp = ' , f - ftmp , ' alpha*t = ' , alpha * t end if end if if ((( f - ftmp ) / 2.0_wp >= alpha * t ) . or . min_alpha_reached ) then if ( me % verbose . and . min_alpha_reached ) then write ( me % iunit , '(A)' ) '        Minimum alpha reached' end if ! Armijo-Goldstein condition is satisfied ! (or the min step has been reached) x = xtmp fvec = fvectmp f = ftmp exit end if alpha = alpha * me % tau ! reduce step size if ( alpha <= me % alpha_min ) then alpha = me % alpha_min min_alpha_reached = . true . ! will stop on the next step end if end do end subroutine backtracking_linesearch !***************************************************************************************** !***************************************************************************************** !> !  An exact linesearch that uses a derivative-free minimizer to !  find the minimum value of `f(x)` between !  `x = xold + p * alpha_min` and !  `x = xold + p * alpha_max`. ! !  Usually this is overkill and not necessary, but is here as an option for testing. subroutine exact_linesearch ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] real ( wp ), dimension (:), allocatable :: xnew !! used in [[func_for_fmin]] real ( wp ) :: alpha_min allocate ( xnew ( me % n )) ! find the minimum value of f in the range of alphas: alpha_min = fmin ( func_for_fmin , me % alpha_min , me % alpha_max , me % fmin_tol ) if ( me % verbose ) write ( me % iunit , '(1P,*(A,1X,E16.6))' ) '        alpha_min = ' , alpha_min x = xold + p * alpha_min if ( all ( x == xnew )) then ! already computed in the func else call me % func ( x , fvec ) f = norm2 ( fvec ) end if contains real ( wp ) function func_for_fmin ( alpha ) !! function for [[fmin]] implicit none real ( wp ), intent ( in ) :: alpha !! indep variable xnew = xold + p * alpha call me % func ( xnew , fvec ) func_for_fmin = norm2 ( fvec ) ! return result f = func_for_fmin ! just in case this is the solution end function func_for_fmin end subroutine exact_linesearch !***************************************************************************************** !***************************************************************************************** !> !  A simple search that just evaluates the function at a specified !  number of points and picks the one with the minimum function value. subroutine fixed_point_linesearch ( me , xold , p , x , f , fvec , fjac , fjac_sparse ) implicit none class ( nlesolver_type ), intent ( inout ) :: me real ( wp ), dimension ( me % n ), intent ( in ) :: xold !! previous value of `x` real ( wp ), dimension ( me % n ), intent ( in ) :: p !! search direction real ( wp ), dimension ( me % n ), intent ( out ) :: x !! new `x` real ( wp ), intent ( inout ) :: f !! magnitude of `fvec` real ( wp ), dimension ( me % m ), intent ( inout ) :: fvec !! function vector real ( wp ), dimension (:,:), intent ( in ), optional :: fjac !! jacobian matrix [dense] real ( wp ), dimension (:), intent ( in ), optional :: fjac_sparse !! jacobian matrix [sparse] integer :: i !! counter integer :: n_points !! number of points to compute real ( wp ), dimension (:), allocatable :: alphas_to_try !! set of `alpha` values to try real ( wp ), dimension (:), allocatable :: x_tmp !! temp `x` real ( wp ), dimension (:), allocatable :: fvec_tmp !! temp `fvec` real ( wp ) :: f_tmp !! temp `f` real ( wp ) :: step_size !! step size for `alpha` integer :: n !! number of steps to divide the interval ! 1 o-----------o ! 2 o-----o-----o ! 3 o---o---o---o n = me % n_intervals n_points = n + 1 allocate ( alphas_to_try ( n_points )) allocate ( x_tmp ( me % n )) allocate ( fvec_tmp ( me % m )) step_size = ( me % alpha_max - me % alpha_min ) / real ( n , wp ) ! compute the alphas: alphas_to_try ( 1 ) = me % alpha_min do i = 2 , n alphas_to_try ( i ) = alphas_to_try ( i - 1 ) + step_size end do alphas_to_try ( n_points ) = me % alpha_max ! now compute the functions at these alphas: f = big do i = 1 , n_points x_tmp = xold + p * alphas_to_try ( i ) ! evaluate the function at tthis point: call me % func ( x_tmp , fvec_tmp ) f_tmp = norm2 ( fvec_tmp ) if ( f_tmp <= f ) then ! new best point x = x_tmp f = f_tmp fvec = fvec_tmp end if end do end subroutine fixed_point_linesearch !***************************************************************************************** !****************************************************************************************************** end module nlesolver_module !******************************************************************************************************","tags":"","loc":"sourcefile/nlesolver_module.f90.html"}]}
\ No newline at end of file
diff --git a/type/nlesolver_type.html b/type/nlesolver_type.html
index 8e7417b..f34368a 100644
--- a/type/nlesolver_type.html
+++ b/type/nlesolver_type.html
@@ -77,7 +77,7 @@ <h1>nlesolver_type
             <li class="list-inline-item" id="statements"><i class="fa fa-list-ol"></i>
               <a data-bs-toggle="tooltip"
                  data-bs-placement="bottom" data-html="true"
-                 title="<p>100.0% of total for derived types.</p>Including implementation: 408 statements, 100.0% of total for derived types.">46 statements</a>
+                 title="<p>100.0% of total for derived types.</p>Including implementation: 437 statements, 100.0% of total for derived types.">46 statements</a>
             </li>
 
             <li class="list-inline-item" id="source-file">
@@ -807,7 +807,11 @@ <h2>Components</h2>
 <td> =</td>
                 <td>0</td>
             <td>
-                
+                <ul>
+<li>0 =&gt; TPP: Threshold Partial   Pivoting.</li>
+<li>1 =&gt; TRP: Threshold Rook      Pivoting.</li>
+<li>2 =&gt; TCP: Threshold Complete  Pivoting.</li>
+</ul>
             </td>
         </tr>
         <tr>
@@ -1031,7 +1035,7 @@ <h4>Arguments</h4>
             <td>::</td>
             <td><strong>fmin_tol</strong></td>
             <td>
-<p>convergence tolerance for <a>fmin</a> (used when <code>step_mode=3</code>)</p>
+<p>convergence tolerance for <a href="../https:/jacobwilliams.github.io/fmin/proc/fmin.html">fmin</a> (used when <code>step_mode=3</code>)</p>
             </td>
         </tr>
         <tr>
@@ -1399,7 +1403,7 @@ <h4>Arguments</h4>
             <td>::</td>
             <td><strong>lusol_method</strong></td>
             <td>
-
+<p><code>LUSOL</code> method:</p><a href="../proc/initialize_nlesolver_variables.html#variable-lusol_method~2" class="pull-right"><emph>Read more&hellip;</emph></a>
             </td>
         </tr>
     </tbody>
@@ -1793,7 +1797,9 @@ <h3><span class="anchor" id="src"></span>Source Code</h3>
 <span class="w">        </span><span class="kt">real</span><span class="p">(</span><span class="n">wp</span><span class="p">)</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">damp</span><span class="w">    </span><span class="o">=</span><span class="w"> </span><span class="n">zero</span><span class="w">  </span><span class="c">!! damp parameter for LSQR</span>
 
 <span class="w">        </span><span class="c">! LUSOL parameters:</span>
-<span class="w">        </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">lusol_method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span>
+<span class="w">        </span><span class="kt">integer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">lusol_method</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="w"> </span><span class="c">!! * 0 =&gt; TPP: Threshold Partial   Pivoting.</span>
+<span class="w">                                    </span><span class="c">!! * 1 =&gt; TRP: Threshold Rook      Pivoting.</span>
+<span class="w">                                    </span><span class="c">!! * 2 =&gt; TCP: Threshold Complete  Pivoting.</span>
 
 <span class="w">        </span><span class="c">! dense version:</span>
 <span class="w">        </span><span class="k">procedure</span><span class="p">(</span><span class="n">grad_func</span><span class="p">),</span><span class="k">pointer</span><span class="w"> </span><span class="kd">::</span><span class="w"> </span><span class="n">grad</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="nb">null</span><span class="p">()</span><span class="w"> </span><span class="c">!! user-supplied routine to compute the gradient of the function (dense version)</span>