[petsc-dev] Broken MatMatMult_MPIAIJ_MPIDense

[Pierre Jolivet]

FWIW, I’ve fixed MatMatMult and MatTransposeMatMult here https://gitlab.com/petsc/petsc/commit/93d7d1d6d29b0d66b5629a261178b832a925de80 <https://gitlab.com/petsc/petsc/commit/93d7d1d6d29b0d66b5629a261178b832a925de80> (with MAT_INITIAL_MATRIX).
I believe there is something not right in your MR (2032) with MAT_REUSE_MATRIX (without having called MAT_INITIAL_MATRIX first), cf. https://gitlab.com/petsc/petsc/merge_requests/2069#note_220269898 <https://gitlab.com/petsc/petsc/merge_requests/2069#note_220269898>.
Of course, I’d love to be proved wrong!

Thanks,
Pierre

> On 22 Sep 2019, at 5:04 PM, Zhang, Hong <hzhang at mcs.anl.gov> wrote:
> 
> I'll check it tomorrow.
> Hong
> 
> On Sun, Sep 22, 2019 at 1:04 AM Pierre Jolivet via petsc-dev <petsc-dev at mcs.anl.gov <mailto:petsc-dev at mcs.anl.gov>> wrote:
> Jed,
> I’m not sure how easy it is to put more than a few lines of code on GitLab, so I’ll just send the (tiny) source here, as a follow-up of our discussion https://gitlab.com/petsc/petsc/merge_requests/2069#note_220229648 <https://gitlab.com/petsc/petsc/merge_requests/2069#note_220229648>.
> Please find attached a .cpp showing the brokenness of C=A*B with A of type MPIAIJ and B of type MPIDense when the LDA of B is not equal to its number of local rows.
> It does [[1,1];[1,1]] * [[0,1,2,3];[0,1,2,3]]
> C should be equal to 2*B, but it’s not, unless lda = m (= 1).
> Mat Object: 2 MPI processes
>   type: mpidense
> 0.0000000000000000e+00 1.0000000000000000e+00 2.0000000000000000e+00 3.0000000000000000e+00
> 0.0000000000000000e+00 1.0000000000000000e+00 2.0000000000000000e+00 3.0000000000000000e+00
> 
> If you change Bm here https://www.mcs.anl.gov/petsc/petsc-dev/src/mat/impls/aij/mpi/mpimatmatmult.c.html#line549 <https://www.mcs.anl.gov/petsc/petsc-dev/src/mat/impls/aij/mpi/mpimatmatmult.c.html#line549> to the LDA of B, you’ll get the correct result.
> Mat Object: 2 MPI processes
>   type: mpidense
> 0.0000000000000000e+00 2.0000000000000000e+00 4.0000000000000000e+00 6.0000000000000000e+00
> 0.0000000000000000e+00 2.0000000000000000e+00 4.0000000000000000e+00 6.0000000000000000e+00
> 
> Unfortunately, w.r.t. MR 2069, I still don’t get the same results with a plain view LDA > m (KO) and a view + duplicate LDA = m (OK).
> So there might be something else to fix (or this might not even be a correct fix), but the only reproducer I have right now is the full solver.
> 
> Thanks,
> Pierre
> 

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