[petsc-users] [petsc-dev] How to compute RARt with A and R as distributed (MPI) matrices ?

[Jed Brown]

Hong <hzhang at mcs.anl.gov> writes:

> Jed:
>>
>> >> Is it better this way or as a fallback when !A->ops->rart?  MatPtAP
>> >> handles other combinations like MAIJ.
>> >>
>> >
>> > Do you mean
>> > if ( !A->ops->rart) {
>> >     Mat Rt;
>> >     ierr = MatTranspose(R,MAT_INITIAL_MATRIX,&Rt);CHKERRQ(ierr);
>> >     ierr = MatMatMatMult(R,A,Rt,scall,fill,C);CHKERRQ(ierr);
>> >     ierr = MatDestroy(&Rt);CHKERRQ(ierr);
>> > }
>> > This does NOT work for most matrix formats because we do not have
>> fallbacks
>> > for MatTranspose() and MatMatMult().
>>
>> That's fine; they'll trigger an error and we'll be able to see from the
>> stack that it can be made to work by either implementing the appropriate
>> MatRARt or MatTranspose and MatMatMatMult.
>>
>
> You prefer adding this default, even though it gives error in either
>  MatTranspose() or MatMatMatMult() depends on input matrix format?

Yeah, in the sense that it gives more opportunities to succeed.

> If so, we need add this type of 'default' to all mat operations --
> currently, all routines do
> if (!mat->ops-> )
> SETERRQ1(PetscObjectComm((PetscObject)mat),PETSC_ERR_SUP,"Mat type
> %s",((PetscObject)mat)->type_name);

Probably.
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