[petsc-users] PCMG with PCREDISTRIBUTE

[Carl-Johan Thore]

Hi,

I'm trying to run an iterative solver (FGMRES for example) with PCMG as preconditioner. The setup of PCMG
is done roughly as in ex42 of the PETSc-tutorials (https://petsc.org/main/src/ksp/ksp/tutorials/ex42.c.html).
Since I have many locked  degrees-of-freedom I would like to use PCREDISTRIBUTE. However, this
results in (30039 is the number of DOFs after redistribute and 55539 the number before):

[0]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
[0]PETSC ERROR: Nonconforming object sizes
[0]PETSC ERROR: Matrix dimensions of A and P are incompatible for MatProductType PtAP: A 30039x30039, P 55539x7803
[0]PETSC ERROR: See https://petsc.org/release/faq/ for trouble shooting.
[0]PETSC ERROR: Petsc Development GIT revision: v3.19.0-238-g512d1ae6db4  GIT Date: 2023-04-24 16:37:00 +0200
[0]PETSC ERROR: topopt on a arch-linux-c-opt Fri Jun 30 13:28:41 2023
[0]PETSC ERROR: Configure options COPTFLAGS="-O3 -march=native" CXXOPTFLAGS="-O3 -march=native" FOPTFLAGS="-O3 -march=native" CUDAOPTFLAGS=-O3 --with-cuda --with-cusp --with-debugging=0 --download-scalapack --download-hdf5 --download-zlib --download-mumps --download-parmetis --download-metis --download-ptscotch --download-hypre --download-spai
[0]PETSC ERROR: #1 MatProductSetFromOptions_Private() at /mnt/c/mathware/petsc/src/mat/interface/matproduct.c:420
[0]PETSC ERROR: #2 MatProductSetFromOptions() at /mnt/c/mathware/petsc/src/mat/interface/matproduct.c:541
[0]PETSC ERROR: #3 MatPtAP() at /mnt/c/mathware/petsc/src/mat/interface/matrix.c:9868
[0]PETSC ERROR: #4 MatGalerkin() at /mnt/c/mathware/petsc/src/mat/interface/matrix.c:10899
[0]PETSC ERROR: #5 PCSetUp_MG() at /mnt/c/mathware/petsc/src/ksp/pc/impls/mg/mg.c:1029
[0]PETSC ERROR: #6 PCSetUp() at /mnt/c/mathware/petsc/src/ksp/pc/interface/precon.c:994
[0]PETSC ERROR: #7 KSPSetUp() at /mnt/c/mathware/petsc/src/ksp/ksp/interface/itfunc.c:406
[0]PETSC ERROR: #8 PCSetUp_Redistribute() at /mnt/c/mathware/petsc/src/ksp/pc/impls/redistribute/redistribute.c:327
[0]PETSC ERROR: #9 PCSetUp() at /mnt/c/mathware/petsc/src/ksp/pc/interface/precon.c:994
[0]PETSC ERROR: #10 KSPSetUp() at /mnt/c/mathware/petsc/src/ksp/ksp/interface/itfunc.c:406
[0]PETSC ERROR: #11 KSPSolve_Private() at /mnt/c/mathware/petsc/src/ksp/ksp/interface/itfunc.c:824
[0]PETSC ERROR: #12 KSPSolve() at /mnt/c/mathware/petsc/src/ksp/ksp/interface/itfunc.c:1070

It’s clear what happens I think, and it kind of make since not all levels are redistributed as they should (?).
Is it possible to use PCMG with PCREDISTRIBUTE in an easy way?

Kind regards,
Carl-Johan
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