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Linear MGRIT implementation #88

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Linear MGRIT implementation #88

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69115c4
First attempt at a linear MGRIT implementation (doesn't work yet)
rfalgout Oct 30, 2021
c9708d0
Merge branch 'master' into linear-pr
rfalgout May 18, 2023
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2 changes: 2 additions & 0 deletions braid/braid.h
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,8 @@
#ifndef braid_HEADER
#define braid_HEADER

#define braid_LINEAR 1

/* To enable XBraid without MPI, re-compile with
* make sequential=yes
* This will compile using the mpistubs.h */
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5 changes: 5 additions & 0 deletions braid/hierarchy.c
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Expand Up @@ -525,6 +525,11 @@ _braid_CopyFineToCoarse(braid_Core core)
_braid_MapCoarseToFine(index, f_cfactor, f_index);
_braid_UGetVector(core, level-1, f_index, &u);
_braid_Coarsen(core, level, f_index, index, u, &va[index-ilower]);
if (braid_LINEAR)
{
/* Set initial guess to zero on coarse grids */
_braid_BaseSum(core, app, -1.0, va[index-ilower], 1.0, va[index-ilower]);
}

_braid_BaseFree(core, app, u);
_braid_BaseClone(core, app, va[index-ilower], &u);
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24 changes: 24 additions & 0 deletions braid/restrict.c
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Expand Up @@ -202,12 +202,22 @@ _braid_FRestrict(braid_Core core,
_braid_MapFineToCoarse(ci, cfactor, c_index);
_braid_Coarsen(core, c_level, ci, c_index, u, &c_va[c_index-c_ilower]);
_braid_Coarsen(core, c_level, ci, c_index, r, &c_fa[c_index-c_ilower]);
if (braid_LINEAR)
{
/* Set initial guess to zero on coarse grids */
_braid_BaseSum(core, app, -1.0, c_va[c_index-c_ilower], 1.0, c_va[c_index-c_ilower]);
}
}
else if (ci == 0)
{
/* Restrict initial condition, coarsening in space if needed */
_braid_UGetVectorRef(core, level, 0, &u);
_braid_Coarsen(core, c_level, 0, 0, u, &c_va[0]);
if (braid_LINEAR)
{
/* Set initial guess to zero on coarse grids */
_braid_BaseSum(core, app, -1.0, c_va[0], 1.0, c_va[0]);
}
}

if ((flo <= fhi) || (ci > _braid_CoreElt(core, initiali)))
Expand All @@ -222,6 +232,12 @@ _braid_FRestrict(braid_Core core,
/* Set initial guess on coarse level */
_braid_InitGuess(core, c_level);

if (braid_LINEAR)
{
/* Don't need to update the rhs in the linear case (no Richardson either) */
}
else
{
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Should we indent this code block?

/* Initialize update of c_va[-1] boundary */
if (c_ilower <= c_iupper)
{
Expand Down Expand Up @@ -329,6 +345,7 @@ _braid_FRestrict(braid_Core core,
}
}
_braid_CommWait(core, &send_handle);
}

/* Compute global rnorm (only on level 0) */
if (level == 0)
Expand Down Expand Up @@ -359,12 +376,19 @@ _braid_FRestrict(braid_Core core,
_braid_PrintSpatialNorms(core, tnorm_a, ncpoints);
}

if (braid_LINEAR)
{
/* Don't need to update the rhs in the linear case (no Richardson either) */
}
else
{
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Should we indent this code block?

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Yes. I wanted the diffs to be clear when I first implemented this.

/* Need to finalize the error estimates at the F-points */
if ( level == 0 && est_error )
{
_braid_FinalizeErrorEstimates( core, estimate , c_iupper-c_ilower + 1 );
_braid_TFree(estimate);
}
}

return _braid_error_flag;
}
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