diff --git a/src/common.hpp b/src/common.hpp
index c9749be..05b722f 100644
--- a/src/common.hpp
+++ b/src/common.hpp
@@ -96,8 +96,8 @@ inline MatrixType RandomUniform(const Eigen::Index numRows,
 
 struct Options
 {
-    int ichunk{0}, chunksize{10000}, K{2}, C{10}, nadmix{1000}, nimpute{40}, nthreads{1}, seed{999};
-    int gridsize{1}, refillHaps{0};
+    int ichunk{0}, chunksize{50000}, K{2}, C{10}, nadmix{1000}, nimpute{40}, nthreads{1}, seed{999};
+    int gridsize{1}, refillHaps{0}, buffer{0};
     double ltol{1e-1}, info{0}, tol_pi{0.99}, tol_r{1e-5};
     double ptol{1e-6}; // threshold for P
     double ftol{1e-6}; // threshold for F
@@ -140,7 +140,8 @@ struct Pars
         P = MyFloat1D(iP.data(), iP.data() + iP.size());
         Q = MyFloat1D(iQ.data(), iQ.data() + iQ.size());
         er = MyFloat1D(ier.data(), ier.data() + ier.size());
-        for(size_t k = 0; k < iF.size(); k++) F.emplace_back(MyFloat1D(iF[k].data(), iF[k].data() + iF[k].size()));
+        for(size_t k = 0; k < iF.size(); k++)
+            F.emplace_back(MyFloat1D(iF[k].data(), iF[k].data() + iF[k].size()));
     }
     int K, C, M, N;
     MyFloat1D P, Q;
@@ -367,8 +368,8 @@ inline MyArr1D get_emission_by_site(const MyArr1D & gli, const MyArr1D & P, doub
             {
                 for(g2 = 0; g2 <= 1; g2++)
                 {
-                    emit(z12) +=
-                        gli(g1 + g2) * (g1 * P(z1) + (1 - g1) * (1 - P(z1))) * (g2 * P(z2) + (1 - g2) * (1 - P(z2)));
+                    emit(z12) += gli(g1 + g2) * (g1 * P(z1) + (1 - g1) * (1 - P(z1)))
+                                 * (g2 * P(z2) + (1 - g2) * (1 - P(z2)));
                 }
             }
         }
@@ -453,8 +454,8 @@ inline auto forward_backwards_diploid(const MyArr2D & emit, const MyArr2D & R, c
             {
                 z12 = z1 * C + z2;
                 alpha(z12, s) = emit(z12, s)
-                                * (alpha(z12, s - 1) * R(0, s) + PI(z1, s) * sumTmp1(z2) + PI(z2, s) * sumTmp1(z1)
-                                   + PI(z1, s) * PI(z2, s) * constTmp);
+                                * (alpha(z12, s - 1) * R(0, s) + PI(z1, s) * sumTmp1(z2)
+                                   + PI(z2, s) * sumTmp1(z1) + PI(z1, s) * PI(z2, s) * constTmp);
             }
         }
         cs(s) = 1.0 / alpha.col(s).sum();
@@ -483,7 +484,8 @@ inline auto forward_backwards_diploid(const MyArr2D & emit, const MyArr2D & R, c
             {
                 z12 = z1 * C + z2;
                 // apply scaling
-                beta(z12, s) = (beta_mult_emit(z12) * R(0, s + 1) + sumTmp1(z1) + sumTmp1(z2) + constTmp) * cs(s + 1);
+                beta(z12, s) =
+                    (beta_mult_emit(z12) * R(0, s + 1) + sumTmp1(z1) + sumTmp1(z2) + constTmp) * cs(s + 1);
             }
         }
     }
diff --git a/src/io.cpp b/src/io.cpp
index d6491c8..3ce6bf2 100644
--- a/src/io.cpp
+++ b/src/io.cpp
@@ -488,28 +488,6 @@ void chunk_beagle_genotype_likelihoods(const std::unique_ptr<BigAss> & genome, c
     // now evenly split last two chunks of each chromosome
 }
 
-void update_bigass_inplace(const std::unique_ptr<BigAss> & genome)
-{
-    int ic, ndiff;
-    for(ic = 0, genome->nsnps = 0; ic < genome->nchunks; ic++) genome->nsnps += genome->pos[ic].size();
-    for(ic = 0; ic < genome->nchunks; ic++)
-    {
-        if(ic == 0) continue; // assume the first chunksize is not greater than the defined
-        if((int)genome->pos[ic - 1].size() < genome->chunksize)
-        {
-            ndiff = genome->chunksize - genome->pos[ic - 1].size();
-            if((int)genome->pos[ic].size() >= ndiff)
-            {
-                genome->pos[ic - 1].insert(genome->pos[ic - 1].end(), genome->pos[ic].begin(),
-                                           genome->pos[ic].begin() + ndiff);
-                Int1D(genome->pos[ic].begin() + ndiff, genome->pos[ic].end()).swap(genome->pos[ic]);
-            }
-            else
-                break;
-        }
-    }
-}
-
 size_t count_lines(std::string fpath)
 {
     std::ifstream ifs(fpath);
@@ -627,3 +605,31 @@ void init_bigass(const std::unique_ptr<BigAss> & genome, const Options & opts)
         cao.error("number of grids should be same as snps if B=1");
     cao.done(tim.date(), "elapsed time for parsing beagle file", std::fixed, tim.reltime(), " secs");
 }
+
+/*
+ * if buffer is desired, re-split chunks
+ */
+void update_bigass(const std::unique_ptr<BigAss> & genome, const Options & opts)
+{
+    assert(opts.buffer > 0);
+    size_t s = opts.buffer * genome->nsamples * 3;
+    for(int ic = 0; ic < genome->nchunks; ic++)
+    {
+        assert(opts.buffer < genome->pos[ic].size());
+        if(ic < genome->nchunks - 1)
+        {
+
+            genome->pos[ic].insert(genome->pos[ic].end(), genome->pos[ic + 1].begin(),
+                                   genome->pos[ic + 1].begin() + opts.buffer);
+            genome->gls[ic].insert(genome->gls[ic].end(), genome->gls[ic + 1].begin(),
+                                   genome->gls[ic + 1].end() + s);
+        }
+        else
+        {
+            genome->pos[ic].insert(genome->pos[ic].begin(), genome->pos[ic - 1].end() - opts.buffer,
+                                   genome->pos[ic - 1].end());
+            genome->gls[ic].insert(genome->gls[ic].begin(), genome->gls[ic - 1].end() - s,
+                                   genome->gls[ic - 1].end());
+        }
+    }
+}
diff --git a/src/io.hpp b/src/io.hpp
index 45ca40e..a07ebe9 100644
--- a/src/io.hpp
+++ b/src/io.hpp
@@ -39,5 +39,6 @@ std::string convert_geno2like(std::vector<uint8_t> bed,
                               std::vector<std::string> marker,
                               const uint64_t nsamples);
 void init_bigass(const std::unique_ptr<BigAss> & genome, const Options & opts);
+void update_bigass(const std::unique_ptr<BigAss> & genome, const Options & opts);
 
 #endif // PHASELESS_IO_H_