[petsc-dev] FieldSplit with different nonzero pattern

[Hong]

Pierre :
The code crashes inside
if (scall == MAT_REUSE_MATRIX) {
...
}
which assumes both original matrix and its submatrices data structures
remain unchanged.
We did not anticipate the usage of looping

>
> 3) change the sparsity pattern of the Mat for one of the field
> 4) do a KSPSolve
>

Can you send us a stand-alone code for this type of application.
We will investigate how to support it.

Hong

I cannot change this calling sequence, because I’d like to nest 3) and 4)
> inside a loop.
> However, I end up with this error during 4):
> [0]PETSC ERROR: Nonconforming object sizes
> [0]PETSC ERROR: Cannot reuse matrix. wrong no of nonzeros
> [0]PETSC ERROR: Petsc Development GIT revision: v3.9-13-g05d412bc58  GIT
> Date: 2018-04-09 08:39:52 -0500
>
> [0]PETSC ERROR: #1 MatCreateSubMatrix_SeqAIJ() line 2330 in
> /Users/jolivet/Documents/repositories/petsc/src/mat/impls/aij/seq/aij.c
> [0]PETSC ERROR: #2 MatCreateSubMatrix_MPIAIJ_SameRowColDist() line 3184
> in /Users/jolivet/Documents/repositories/petsc/src/mat/
> impls/aij/mpi/mpiaij.c
> [0]PETSC ERROR: #3 MatCreateSubMatrix_MPIAIJ() line 3310 in
> /Users/jolivet/Documents/repositories/petsc/src/mat/impls/aij/mpi/mpiaij.c
> [0]PETSC ERROR: #4 MatCreateSubMatrix() line 7813 in
> /Users/jolivet/Documents/repositories/petsc/src/mat/interface/matrix.c
> [0]PETSC ERROR: #5 PCSetUp_FieldSplit() line 564 in
> /Users/jolivet/Documents/repositories/petsc/src/ksp/pc/
> impls/fieldsplit/fieldsplit.c
> [0]PETSC ERROR: #6 PCSetUp() line 923 in /Users/jolivet/Documents/
> repositories/petsc/src/ksp/pc/interface/precon.c
> [0]PETSC ERROR: #7 PCApply() line 453 in /Users/jolivet/Documents/
> repositories/petsc/src/ksp/pc/interface/precon.c
> [0]PETSC ERROR: #8 KSP_PCApply() line 276 in /Users/jolivet/repo/petsc/
> include/petsc/private/kspimpl.h
> [0]PETSC ERROR: #9 KSPFGMRESCycle() line 166 in /Users/jolivet/Documents/
> repositories/petsc/src/ksp/ksp/impls/gmres/fgmres/fgmres.c
> [0]PETSC ERROR: #10 KSPSolve_FGMRES() line 291 in /Users/jolivet/Documents/
> repositories/petsc/src/ksp/ksp/impls/gmres/fgmres/fgmres.c
> [0]PETSC ERROR: #11 KSPSolve() line 669 in /Users/jolivet/Documents/
> repositories/petsc/src/ksp/ksp/interface/itfunc.c
>
> Is this the expected behaviour? Would you need a MWE?
> What I find funny is that if I turn -info on, then just before the error,
> I get:
> [0] PCSetUp(): Setting up PC with different nonzero pattern
> So why is it trying to reuse the matrix? I am missing a call to some
> function?
>
> Thanks in advance,
> Pierre
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