[petsc-dev] trying to make MKL work with GAMG

[Mark Adams]

On Wed, Jul 4, 2018 at 3:01 AM Richard Tran Mills <rtmills at anl.gov> wrote:

> Hi Mark,
>
> I'd never looked at the code for MatCreateMPIAIJWithSeqAIJ(), but it looks
> like if you are using MPIAIJ matrices but you've set "-mat_seqaij_type
> seqaijmkl",
>

No, I am using -mat_type aijmkl


> then the "diagonal" portion of the MPIAIJ matrix ends up as a SEQAIJMKL
> instance, but the off-diagonal portion ends up as a plain SEQAIJ when it is
> created with MatCreateSeqAIJWithArrays(). (I have not stepped through this
> with a debugger to verify that this is actually what happens.) So, if we
> want the off-diagonal matrix to also be a SEQAIJMKL, then we either need to
> add some logic after the MatCreateSeqAIJWithArrays() call to check to see
> if a different subtype of SEQAIJ is being used and then convert it to the
> correct type, or we need a variant of MatCreateSeqAIJWithArrays() that will
> honor the subtype of SEQAIJ that we are using. Barry, since you added the
> concept of subtyping for SEQAIJ, what do you prefer?
>
> No preference.


> I note that in some (most?) cases, I think we are OK or even better off
> with the off-diagonal matrix in the MPIAIJ not being a SEQAIJMKL one,
> because the PETSc routines can used the "compressed row" stuff to speed up
> handling the many zero rows that often end up in the off-diagonal, whereas
> the MKL routines cannot.
>
>
OK , I'll keep that in mind. I pushed a branch with fixes to get my gamg
tests working (ksp ex56 primarily). I'm going to make a new branch and
try "-mat_seqaij_type
seqaijmkl".

Thanks,
Mark


> --Richard
>
> On Tue, Jul 3, 2018 at 4:31 PM, Mark Adams <mfadams at lbl.gov> wrote:
>
>> I have having to fix AIJ methods that don't get the type from the args to
>> set created matrix type, so as to keep the MKL typing.
>>
>> I am not sure how to fix this because I don't know to say 'make MPI from
>> SEQ' in this method
>>
>> PetscErrorCode MatCreateMPIAIJWithSeqAIJ(MPI_Comm comm,Mat A,Mat B,const
>> PetscInt garray[],Mat *mat)
>> {
>>  ....
>>   ierr = MatCreate(comm,mat);CHKERRQ(ierr);
>>   ierr = MatGetSize(A,&m,&n);CHKERRQ(ierr);
>> ....
>>   ierr = MatSetSizes(*mat,m,n,PETSC_DECIDE,N);CHKERRQ(ierr);
>>   ierr = MatSetType(*mat,MATMPIAIJ);CHKERRQ(ierr);
>>
>> How should I do this?  Other places in the code I get the type from input
>> (MPI) args and set created matrix types accordingly. I could just put a
>> switch with an error for any new types that might come along in the future
>> ...
>>
>> Mark
>>
>
>
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