[petsc-dev] FieldSplit with different nonzero pattern

[Hong]

Pierre:

> Hong,
> Thank you for the patch.
> Our application is not crashing anymore.
> Hopefully this will be merged quickly in master.
>
Merged to master.
Hong

>
>
> On 7 May 2018, at 10:07 PM, Hong <hzhang at mcs.anl.gov> wrote:
>
> Pierre:
> I added this support
> https://bitbucket.org/petsc/petsc/commits/ef7efd37182b12f7b7ab7c34390aae
> 8e592a83c2
>
> It is in branch hzhang/fix-pc-fieldsplit-reuse.
> You may give it a try. Once it passed all our regression tests, it will be
> merged to petsc-master branch.
>
> Your modified ex42.c is very helpful, thanks!
> Hong
>
> On Fri, May 4, 2018 at 10:15 AM, Hong <hzhang at mcs.anl.gov> wrote:
>
>> Pierre:
>> Thanks for creating this use case. I'll check it and get back to you
>> sometime next week.
>> Hong
>>
>> Hong,
>>> Thanks for your reply.
>>> It’s not so minimalist, but at least it is based on one of your example.
>>> diff --git a/src/ksp/ksp/examples/tutorials/ex42.c
>>> b/src/ksp/ksp/examples/tutorials/ex42.c
>>> index 8be4389a2d..520c82569a 100644
>>> --- a/src/ksp/ksp/examples/tutorials/ex42.c
>>> +++ b/src/ksp/ksp/examples/tutorials/ex42.c
>>> @@ -1953,6 +1953,15 @@ static PetscErrorCode
>>> solve_stokes_3d_coupled(PetscInt mx,PetscInt my,PetscInt m
>>>      }
>>>    }
>>>    ierr = KSPSolve(ksp_S,f,X);CHKERRQ(ierr);
>>> +  PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,
>>> PETSC_VIEWER_ASCII_INFO);
>>> +  MatView(A, PETSC_VIEWER_STDOUT_WORLD);
>>> +  Mat C;
>>> +  MatMatMult(A, A, MAT_INITIAL_MATRIX, PETSC_DEFAULT, &C);
>>> +  MatView(C, PETSC_VIEWER_STDOUT_WORLD);
>>> +  PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
>>> +  ierr = KSPSetOperators(ksp_S,C,C);CHKERRQ(ierr);
>>> +  ierr = KSPSolve(ksp_S,f,X);CHKERRQ(ierr);
>>> +  MatDestroy(&C);
>>>
>>>    ierr = PetscOptionsGetBool(NULL,NULL,"-write_pvts",&write_output,NU
>>> LL);CHKERRQ(ierr);
>>>    if (write_output) {ierr = DAView3DPVTS(da_Stokes,X,"up")
>>> ;CHKERRQ(ierr);}
>>>
>>> $ mpirun -np 1 ./ex42 -mx 2 -my 2 -mz 2 -stokes_pc_type fieldsplit
>>> This should give you this exact error.
>>> Do you know of a way to bypass the error by flushing/destroying the PC
>>> while still keeping the options for the following KSPSolve?
>>>
>>> Thanks in advance,
>>> Pierre
>>>
>>> On 3 May 2018, at 5:07 PM, Hong <hzhang at mcs.anl.gov> wrote:
>>>
>>> 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/ai
>>>> j/mpi/mpiaij.c
>>>> [0]PETSC ERROR: #3 MatCreateSubMatrix_MPIAIJ() line 3310 in
>>>> /Users/jolivet/Documents/repositories/petsc/src/mat/impls/ai
>>>> j/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/repos
>>>> itories/petsc/src/ksp/pc/interface/precon.c
>>>> [0]PETSC ERROR: #7 PCApply() line 453 in /Users/jolivet/Documents/repos
>>>> itories/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/impl
>>>> s/gmres/fgmres/fgmres.c
>>>> [0]PETSC ERROR: #10 KSPSolve_FGMRES() line 291 in
>>>> /Users/jolivet/Documents/repositories/petsc/src/ksp/ksp/impl
>>>> s/gmres/fgmres/fgmres.c
>>>> [0]PETSC ERROR: #11 KSPSolve() line 669 in
>>>> /Users/jolivet/Documents/repositories/petsc/src/ksp/ksp/inte
>>>> rface/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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