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

Fri Aug 12 10:49:15 CDT 2016

Gaetan, This was simple, if you are setup to easily check this you can test
this in my branch mark/gamg-aijcheck -- you should get an error message
"Require AIJ matrix."
Thanks again,

On Fri, Aug 12, 2016 at 11:08 AM, Gaetan Kenway <gaetank at gmail.com> wrote:

> 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/imp
>>> ls/gamg/util.c
>>> [0]PETSC ERROR: #3 PCGAMGGraph_AGG() line 908 in
>>> /Users/lmitche1/Documents/work/src/deps/petsc/src/ksp/pc/imp
>>> ls/gamg/agg.c
>>> [0]PETSC ERROR: #4 PCSetUp_GAMG() line 525 in
>>> /Users/lmitche1/Documents/work/src/deps/petsc/src/ksp/pc/imp
>>> ls/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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