[petsc-dev] Segmentation faults in MatMatMult & MatTransposeMatMult

[Dave May]

On Tue, 15 Jan 2019 at 05:18, Pierre Jolivet via petsc-dev <
petsc-dev at mcs.anl.gov> wrote:

> Cf. the end of my sentence: "(I know, I could switch to SeqAIJ_SeqDense,
> but that is not an option I have right now)”
> All my Mat are of type MATMPIX. Switching to MATX here as you suggested
> would mean that I need to add a bunch of if(comm_size == 1)
> MatSeqXSetPreallocation else MatMPIXSetPreallocation in the rest of my
> code, which is something I would rather avoid.
>

Actually this is not the case.

If you do as Hong suggests and use MATAIJ then the switch for comm_size for
Seq or MPI is done internally to MatCreate and is not required in the user
code. Additionally, in your preallocation routine, you can call safely both
(without your comm_size if statement)
MatSeqAIJSetPreallocation()
and
MatMPIAIJSetPreallocation()
If the matrix type matches that expected by the API, then it gets executed.
Otherwise nothing happens.

This is done all over the place to enable the matrix type to be a run-time
choice.

For example, see here
https://www.mcs.anl.gov/petsc/petsc-current/src/dm/impls/da/fdda.c.html#DMCreateMatrix_DA_3d_MPIAIJ
and look at lines 1511 and 1512.

Thanks,
  Dave





>
> Thanks,
> Pierre
>
> On 14 Jan 2019, at 10:30 PM, Zhang, Hong <hzhang at mcs.anl.gov> wrote:
>
> Replace
> ierr = MatSetType(A, MATMPIAIJ);CHKERRQ(ierr);
> to
> ierr = MatSetType(A, MATAIJ);CHKERRQ(ierr);
>
> Replace
> ierr = MatSetType(B, MATMPIDENSE)i;CHKERRQ(ierr);
> to
> ierr = MatSetType(B, MATDENSE)i;CHKERRQ(ierr);
>
> Then add
> MatSeqAIJSetPreallocation()
> MatSeqDenseSetPreallocation()
>
> Hong
>
> On Mon, Jan 14, 2019 at 2:51 PM Pierre Jolivet via petsc-dev <
> petsc-dev at mcs.anl.gov> wrote:
>
>> Hello,
>> Is there any chance to get MatMatMult_MPIAIJ_MPIDense  and
>> MatTransposeMatMult_MPIAIJ_MPIDense fixed so that the attached program
>> could run _with a single_ process? (I know, I could switch to
>> SeqAIJ_SeqDense, but that is not an option I have right now)
>>
>> Thanks in advance,
>> Pierre
>>
>>
>
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