[petsc-dev] Segmentation faults in MatMatMult & MatTransposeMatMult

[Dave May]

On Tue, 15 Jan 2019 at 08:50, Pierre Jolivet <pierre.jolivet at enseeiht.fr>
wrote:

> OK, I was wrong about MATAIJ, as Jed already pointed out.
> What about BAIJ or Dense matrices?
>

The preallocation methods for BAIJ and Dense both internally use
PetscTryMethod.



> What about VecCreateMPIWithArray which seems to explicitly call VecCreate_MPI_Private
> which explicitly sets the type to VECMPI
> https://www.mcs.anl.gov/petsc/petsc-current/src/vec/vec/impls/mpi/pbvec.c.html#line522 so
> that I cannot do a MatMult with a MATAIJ with a communicator of size 1?
>

That looks problematic.

Possibly there should either be an if statement in VecCreateMPIWithArray()
associated with the comm size, or there should be a new API
VecCreateWithArray() with the same args as VecCreateMPIWithArray.

As a work around, you could add VecCreateWithArray() in your code base
which does the right thing.



>
> Thanks,
> Pierre
>
> On 15 Jan 2019, at 9:40 AM, Dave May <dave.mayhem23 at gmail.com> wrote:
>
>
>
> 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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