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

[Gaetan Kenway]

Thanks Mark

I haven't been able to try it, but I trust the error message will show up.
That's always better than I seg fault.

I may have a few more questions later when I try to make it work well, but
Ill leave that for another thread

Thanks,
Gaetan

On Fri, Aug 12, 2016 at 11:49 AM, Mark Adams <mfadams at lbl.gov> wrote:

> 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/interf
>>>> ace/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(ier
>>>> r);
>>>>
>>>>
>>>> ...
>>>>           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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