[petsc-users] On PCFIELDSPLIT and its implementation

[Matthew Knepley]

Fields are numbered from 0.

  Thanks,

     Matt

On Wed, Nov 9, 2022 at 2:20 AM Edoardo alinovi <edoardo.alinovi at gmail.com>
wrote:

> Hello guys,
>
> I am getting this error while using fieldsplit:
>
> [3]PETSC ERROR: --------------------- Error Message
> --------------------------------------------------------------
>
> *[3]PETSC ERROR: Nonconforming object sizes[3]PETSC ERROR: Local column
> sizes 6132 do not add up to total number of columns 9200*
> [3]PETSC ERROR: See https://petsc.org/release/faq/ for trouble shooting.
> [3]PETSC ERROR: Petsc Development GIT revision: v3.18.1-191-g32ed6ae2ff2
>  GIT Date: 2022-11-08 12:22:17 -0500
> [3]PETSC ERROR: flubio_coupled on a gnu named alienware by edo Wed Nov  9
> 08:16:29 2022
> [3]PETSC ERROR: Configure options PETSC_ARCH=gnu FOPTFLAGS=-O3
> COPTFLAGS=-O3 CXXOPTFLAGS=-O3 -with-debugging=no -download-fblaslapack=1
> -download-superlu_dist -download-mumps -download-hypre -download-metis
> -download-parmetis -download-scalapack -download-ml -download-slepc
> -download-hpddm -download-cmake
> -with-mpi-dir=/home/edo/software/openmpi-4.1.1/build/
> [3]PETSC ERROR: #1 MatCreateSubMatrix_MPIBAIJ_Private() at
> /home/edo/software/petsc/src/mat/impls/baij/mpi/mpibaij.c:1987
> [3]PETSC ERROR: #2 MatCreateSubMatrix_MPIBAIJ() at
> /home/edo/software/petsc/src/mat/impls/baij/mpi/mpibaij.c:1911
> [3]PETSC ERROR: #3 MatCreateSubMatrix() at
> /home/edo/software/petsc/src/mat/interface/matrix.c:8340
> [3]PETSC ERROR: #4 PCSetUp_FieldSplit() at
> /home/edo/software/petsc/src/ksp/pc/impls/fieldsplit/fieldsplit.c:657
> [3]PETSC ERROR: #5 PCSetUp() at
> /home/edo/software/petsc/src/ksp/pc/interface/precon.c:994
> [3]PETSC ERROR: #6 KSPSetUp() at
> /home/edo/software/petsc/src/ksp/ksp/interface/itfunc.c:406
> [3]PETSC ERROR: #7 KSPSolve_Private() at
> /home/edo/software/petsc/src/ksp/ksp/interface/itfunc.c:825
> [3]PETSC ERROR: #8 KSPSolve() at
> /home/edo/software/petsc/src/ksp/ksp/interface/itfunc.c:1071
>
> Do you have any ideas? Probably something missing in my brief
> implementation here:
>
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> *            call PCSetType(mypc, PCFIELDSPLIT, ierr)              call
> PCFieldSplitSetBlockSize(mypc, 4-bdim, ierr)           *
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> *            !2D, 3x3 block            if(bdim==1) then
> ufields(1) = 0                ufields(2) = 1                pfields(1) = 2
>               call PCFieldSplitSetFields(mypc, "u", 2, ufields, ufields,
> ierr)                call PCFieldSplitSetFields(mypc, "p", 1, pfields,
> pfields, ierr)             ! 3D 4x4 block            else
> ufields(1) = 0                ufields(2) = 1                ufields(3) = 2
>               pfields(1) = 3                call
> PCFieldSplitSetFields(mypc, "u", 3, ufields, ufields, ierr)
> call PCFieldSplitSetFields(mypc, "p", 1, pfields, pfields, ierr)
> endif                         ! Field split type ADDITIVE, MULTIPLICATIVE
> (default), SYMMETRIC_MULTIPLICATIVE, SPECIAL, SCHUR            call
> PCFieldSplitSetType(mypc, PC_COMPOSITE_SCHUR, ierr)*
>
> Thanks for the help!
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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