[petsc-users] MatMatMult with MAT_INITIAL_MATRIX

[Zhang, Hong]

Marius,
C1 = Ampidense*Bmpiaij inherits the number of local rows from A and the number of local columns from B.
C2 = Ampidense*Bmpidense is computed via external package Elemental, which petsc does not dictate the parallel layout of C2 in current petsc/elemental interface. I am not sure if we can do it. Do you want C2 maintains local number of A?
Hong

________________________________
From: petsc-users <petsc-users-bounces at mcs.anl.gov> on behalf of Stefano Zampini <stefano.zampini at gmail.com>
Sent: Sunday, April 19, 2020 11:26 AM
To: Marius Buerkle <mbuerkle at web.de>
Cc: PETSc users list <petsc-users at mcs.anl.gov>
Subject: Re: [petsc-users] MatMatMult with MAT_INITIAL_MATRIX

Matrix C should always inherit the number of local rows from A and the number of local columns from B. Is it not the case for your code? If so, please provide a MWE to reproduce
Also, which version of PETSc are you using?

Il Dom 19 Apr 2020, 19:21 Marius Buerkle <mbuerkle at web.de<mailto:mbuerkle at web.de>> ha scritto:

Hi,

I have a question about the behavior of MAT_INITIAL_MATRIX for MatMatMult. I a have a set of MPIDENSE and MPIAIJ matrices for which I have defined the number of local rows (and local columns) manually, i.e. not used PETSC_DECIDE for MatSetSizes. The number of local rows is different from what PETSC_DECIDE would choose. If I do a MatMatMult with A=MPIDENSE and B=MPIAIJ with MAT_INITIAL_MATRIX then matrix C will have the number of local rows corresponding to A and B, namely what I have defined with MatSetSizes when creating the matrices A and B. But when both matrices are dense, A=MPIDENSE and B=MPIDENSE, then the resulting matrix C will have different number of local rows, namely what I would get with if I would create the matrix with PETSC_DECIDE. Is this behavior normal? The problem is that I have to multiply both resulting matrices which will then throw a "Nonconforming object sizes error" as they have different number of local rows. Any ideas what goes wrong here?


Marius
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