[petsc-dev] Bug in MatZeroRows_MPIAIJ

[Barry Smith]

> On Jun 22, 2016, at 1:24 AM, Lisandro Dalcin <dalcinl at gmail.com> wrote:
> 
> On 22 June 2016 at 00:30, Barry Smith <bsmith at mcs.anl.gov> wrote:
>> Why not just remove the first if test (below) and just have the two conditions diag != 0.0 and drag == 0.0
>> 
>>     if ((diag != 0.0) && (mat->A->rmap->N == mat->A->cmap->N)) {
>>        ierr = MatZeroRows(mat->A, len, lrows, diag, NULL, NULL);CHKERRQ(ierr);
> 
> What about comparing mat->rmap->N and mat->cmap->N, then compare
> size(mat->rmap->comm) and size(mat->cmap->comm), and finally compare
> (memcmp) mat->rmap-range and mat->rmap-range? If everything matches,
> the row&col layout is square, you know that in all processes so no
> need to do reductions, and then  you can take the fast path zeroing
> rows on the diagonal block mat->A.

   By then it is worth the optimization?

> 
> 
> -- 
> Lisandro Dalcin
> ============
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