[petsc-users] [petsc-maint] GAMG with PETSc

[Gaetan Kenway]

Thanks.

When I put the type back to mpiaij, my code runs fine without segfaults
with GAMG.  It doesn't work very well yet, but that is a separate issue.

Gaetan

On Fri, Aug 12, 2016 at 11:03 AM, Mark Adams <mfadams at lbl.gov> wrote:

> Yes, we should check the type.
>
> #define MATAIJ             "aij"
> #define MATSEQAIJ          "seqaij"
> #define MATMPIAIJ          "mpiaij"
>
> I assume that MATAIJ is mapped to SEQ or MPI, and so just need to check
> for the latter two.  I'll do that now.
>
> Thanks,
> Mark
>
> On Fri, Aug 12, 2016 at 7:02 AM, Lawrence Mitchell <
> lawrence.mitchell at imperial.ac.uk> wrote:
>
>> [Added petsc-maint to cc, since I think this is an actual bug]
>>
>> > On 12 Aug 2016, at 01:16, Gaetan Kenway <gaetank at gmail.com> wrote:
>> >
>> > Hi
>> >
>> > I'm attempting to try out using GAMG for a preconditioner for my
>> compressible CFD problem. However, I'm getting segfaults when trying to run
>> the code. The code is based on ksp ex23.c which is attached. It just reads
>> in two precomputed matrices (the actual jacobian and an approximate
>> jacobian used to build the PC) and solves with a RHS of ones.
>> >
>> > My normal approach to solving the system is with ASM+ILU. With the
>> following options, everything works fine.
>>
>> This appears to be a problem that GAMG doesn't work with BAIJ matrices.
>>
>> But there is no checking of the input matrix type anywhere.
>>
>> For example, with a debug PETSc:
>>
>> cd src/ksp/ksp/examples/tutorials
>> make ex23
>> ./ex23 -pc_type gamg -mat_type baij
>>
>> [0]PETSC ERROR: --------------------- Error Message
>> --------------------------------------------------------------
>> [0]PETSC ERROR: Object is in wrong state
>> [0]PETSC ERROR: Must call MatXXXSetPreallocation() or MatSetUp() on
>> argument 1 "mat" before MatSetValues()
>> [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html
>> for trouble shooting.
>> [0]PETSC ERROR: Petsc Development GIT revision: v3.7.3-1123-g21143a8  GIT
>> Date: 2016-08-08 17:24:17 -0700
>> [0]PETSC ERROR: ./ex23 on a arch-darwin-c-dbg named yam-laptop.local by
>> lmitche1 Fri Aug 12 11:51:17 2016
>> [0]PETSC ERROR: Configure options --download-chaco=1 --download-ctetgen=1
>> --download-exodusii=1 --download-hdf5=1 --download-hypre=1
>> --download-metis=1 --download-ml=1 --download-mumps=1 --download-netcdf=1
>> --download-parmetis=1 --download-ptscotch=1 --download-scalapack=1
>> --download-triangle=1 --with-c2html=0 --with-debugging=1
>> --with-shared-libraries=1 PETSC_ARCH=arch-darwin-c-dbg
>> [0]PETSC ERROR: #1 MatSetValues() line 1195 in
>> /Users/lmitche1/Documents/work/src/deps/petsc/src/mat/interface/matrix.c
>> [0]PETSC ERROR: #2 PCGAMGFilterGraph() line 342 in
>> /Users/lmitche1/Documents/work/src/deps/petsc/src/ksp/pc/
>> impls/gamg/util.c
>> [0]PETSC ERROR: #3 PCGAMGGraph_AGG() line 908 in
>> /Users/lmitche1/Documents/work/src/deps/petsc/src/ksp/pc/impls/gamg/agg.c
>> [0]PETSC ERROR: #4 PCSetUp_GAMG() line 525 in
>> /Users/lmitche1/Documents/work/src/deps/petsc/src/ksp/pc/
>> impls/gamg/gamg.c
>> [0]PETSC ERROR: #5 PCSetUp() line 968 in /Users/lmitche1/Documents/work
>> /src/deps/petsc/src/ksp/pc/interface/precon.c
>> [0]PETSC ERROR: #6 KSPSetUp() line 393 in /Users/lmitche1/Documents/work
>> /src/deps/petsc/src/ksp/ksp/interface/itfunc.c
>> [0]PETSC ERROR: #7 KSPSolve() line 602 in /Users/lmitche1/Documents/work
>> /src/deps/petsc/src/ksp/ksp/interface/itfunc.c
>> [0]PETSC ERROR: #8 main() line 158 in /Users/lmitche1/Documents/work
>> /src/deps/petsc/src/ksp/ksp/examples/tutorials/ex23.c
>> [0]PETSC ERROR: PETSc Option Table entries:
>> [0]PETSC ERROR: -mat_type baij
>> [0]PETSC ERROR: -pc_type gamg
>> [0]PETSC ERROR: ----------------End of Error Message -------send entire
>> error message to petsc-maint at mcs.anl.gov----------
>>
>> Looking in PCGAMGFilterGraph I see:
>>
>>   ierr = MatGetType(Gmat,&mtype);CHKERRQ(ierr);
>>   ierr = MatCreate(comm, &tGmat);CHKERRQ(ierr);
>>   ierr = MatSetSizes(tGmat,nloc,nloc,MM,MM);CHKERRQ(ierr);
>>   ierr = MatSetBlockSizes(tGmat, 1, 1);CHKERRQ(ierr);
>>   ierr = MatSetType(tGmat, mtype);CHKERRQ(ierr);
>>   ierr = MatSeqAIJSetPreallocation(tGmat,0,d_nnz);CHKERRQ(ierr);
>>   ierr = MatMPIAIJSetPreallocation(tGmat,0,d_nnz,0,o_nnz);CHKERRQ(ierr);
>>
>>
>> ...
>>           ierr = MatSetValues(tGmat,1,&Ii,1,&id
>> x[jj],&sv,ADD_VALUES);CHKERRQ(ierr);
>>
>>
>> So if Gmat is neither SEQAIJ nor MPIAIJ, then no preallocation has
>> happened (and MatSetUp is not called).
>>
>> Fixing the few instances here by just changing the type of these matrices
>> to AIJ.  One runs into to the problem that creating the coarse grid
>> operators doesn't work, since MatMatMult and friends do not exist for BAIJ
>> matrices.
>>
>> I guess GAMG could MatConvert from BAIJ to AIJ (but this uses extra
>> memory).
>>
>> But it should probably barf with a comprehensible error message.
>>
>> Thoughts?
>>
>> Lawrence
>>
>>
>
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