[petsc-users] GAMG Indefinite

Sun May 22 16:29:37 CDT 2016

Humm, maybe we have version mixup:

src/ksp/ksp/impls/cheby/cheby.c:    ierr =
PetscOptionsBool("-ksp_chebyshev_esteig_random","Use random right hand side
for
estimate","KSPChebyshevEstEigSetUseRandom",cheb->userandom,&cheb->userandom

Also, you should use CG. These other options are the defaults but CG is not:

-mg_levels_esteig_ksp_type cg
-mg_levels_esteig_ksp_max_it 10
-mg_levels_ksp_chebyshev_esteig 0,0.05,0,1.05

Anyway. you can also run with -info, which will be very noisy, but just
grep for GAMG and send me that.

Mark

On Sat, May 21, 2016 at 6:03 PM, Sanjay Govindjee <s_g at berkeley.edu> wrote:

> Mark,
>   I added the option you mentioned but it seems not to use it;
> -options_left reports:
>
> #PETSc Option Table entries:
> -ksp_chebyshev_esteig_random
> -ksp_monitor
> -ksp_type cg
> -log_view
> -options_left
> -pc_gamg_agg_nsmooths 1
> -pc_gamg_type agg
> -pc_type gamg
> #End of PETSc Option Table entries
> There is one unused database option. It is:
> Option left: name:-ksp_chebyshev_esteig_random (no value)
>
>
>
> On 5/21/16 12:36 PM, Mark Adams wrote:
>
> Barry, this is probably the Chebyshev problem.
>
> Sanjay, this is fixed but has not yet been moved to the master branch.
> You can fix this now with with -ksp_chebyshev_esteig_random.  This should
> recover v3.5 semantics.
>
> Mark
>
> On Thu, May 19, 2016 at 2:42 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>>
>>    We see this occasionally, there is nothing in the definition of GAMG
>> that guarantees a positive definite preconditioner even if the operator was
>> positive definite so we don't think this is a bug in the code. We've found
>> using a slightly stronger smoother, like one more smoothing step seems to
>> remove the problem.
>>
>>    Barry
>>
>> > On May 19, 2016, at 1:07 PM, Sanjay Govindjee <s_g at berkeley.edu> wrote:
>> >
>> > I am trying to solve a very ordinary nonlinear elasticity problem
>> > using -ksp_type cg -pc_type gamg in PETSc 3.7.0, which worked fine
>> > in PETSc 3.5.3.
>> >
>> > The problem I am seeing is on my first Newton iteration, the Ax=b
>> > solve returns with and Indefinite Preconditioner error
>> (KSPGetConvergedReason == -8):
>> > (log_view.txt output also attached)
>> >
>> >   0 KSP Residual norm 8.411630828687e-02
>> >   1 KSP Residual norm 2.852209578900e-02
>> >   NO CONVERGENCE REASON:  Indefinite Preconditioner
>> >   NO CONVERGENCE REASON:  Indefinite Preconditioner
>> >
>> > On the next and subsequent Newton iterations, I see perfectly normal
>> > behavior and the problem converges quadratically.  The results look
>> fine.
>> >
>> > I tried the same problem with -pc_type jacobi as well as super-lu, and
>> mumps
>> > and they all work without complaint.
>> >
>> > My run line for GAMG is:
>> > -ksp_type cg -ksp_monitor -log_view -pc_type gamg -pc_gamg_type agg
>> -pc_gamg_agg_nsmooths 1 -options_left
>> >
>> > The code flow looks like:
>> >
>> > ! If no matrix allocation yet
>> > if(Kmat.eq.0) then
>> >   call MatCreate(PETSC_COMM_WORLD,Kmat,ierr)
>> >   call
>> MatSetSizes(Kmat,numpeq,numpeq,PETSC_DETERMINE,PETSC_DETERMINE,ierr)
>> >   call MatSetBlockSize(Kmat,nsbk,ierr)
>> >   call MatSetFromOptions(Kmat, ierr)
>> >   call MatSetType(Kmat,MATAIJ,ierr)
>> >   call
>> MatMPIAIJSetPreallocation(Kmat,PETSC_NULL_INTEGER,mr(np(246)),PETSC_NULL_INTEGER,mr(np(247)),ierr)
>> >   call
>> MatSeqAIJSetPreallocation(Kmat,PETSC_NULL_INTEGER,mr(np(246)),ierr)
>> > endif
>> >
>> > call MatZeroEntries(Kmat,ierr)
>> >
>> > ! Code to set values in matrix
>> >
>> > call MatAssemblyBegin(Kmat, MAT_FINAL_ASSEMBLY, ierr)
>> > call MatAssemblyEnd(Kmat, MAT_FINAL_ASSEMBLY, ierr)
>> > call MatSetOption(Kmat,MAT_NEW_NONZERO_LOCATIONS,PETSC_TRUE,ierr)
>> >
>> > ! If no rhs allocation yet
>> > if(rhs.eq.0) then
>> >   call VecCreate        (PETSC_COMM_WORLD, rhs, ierr)
>> >   call VecSetSizes      (rhs, numpeq, PETSC_DECIDE, ierr)
>> >   call VecSetFromOptions(rhs, ierr)
>> > endif
>> >
>> > ! Code to set values in RHS
>> >
>> > call VecAssemblyBegin(rhs, ierr)
>> > call VecAssemblyEnd(rhs, ierr)
>> >
>> > if(kspsol_exists) then
>> >   call KSPDestroy(kspsol,ierr)
>> > endif
>> >
>> > call KSPCreate(PETSC_COMM_WORLD, kspsol   ,ierr)
>> > call KSPSetOperators(kspsol, Kmat, Kmat, ierr)
>> > call KSPSetFromOptions(kspsol,ierr)
>> > call KSPGetPC(kspsol, pc ,      ierr)
>> >
>> > call PCSetCoordinates(pc,ndm,numpn,hr(np(43)),ierr)
>> >
>> > call KSPSolve(kspsol, rhs, sol, ierr)
>> > call KSPGetConvergedReason(kspsol,reason,ierr)
>> >
>> > ! update solution, go back to the top
>> >
>> > reason is coming back as -8 on my first Ax=b solve and 2 or 3 after that
>> > (with gamg).  With the other solvers it is coming back as 2 or 3 for
>> > iterative options and 4 if I use one of the direct solvers.
>> >
>> > Any ideas on what is causing the Indefinite PC on the first iteration
>> with GAMG?
>> >
>> > Thanks in advance,
>> > -sanjay
>> >
>> > --
>> > -----------------------------------------------
>> > Sanjay Govindjee, PhD, PE
>> > Professor of Civil Engineering
>> >
>> > 779 Davis Hall
>> > University of California
>> > Berkeley, CA 94720-1710
>> >
>> > Voice:  +1 510 642 6060
>> > FAX:    +1 510 643 5264
>> >
>> > s_g at berkeley.edu
>> > http://www.ce.berkeley.edu/~sanjay
>> >
>> > -----------------------------------------------
>> >
>> > Books:
>> >
>> > Engineering Mechanics of Deformable
>> > Solids: A Presentation with Exercises
>> >
>> >
>> http://www.oup.com/us/catalog/general/subject/Physics/MaterialsScience/?view=usa&ci=9780199651641
>> > http://ukcatalogue.oup.com/product/9780199651641.do
>> > http://amzn.com/0199651647
>> >
>> >
>> > Engineering Mechanics 3 (Dynamics) 2nd Edition
>> >
>> > http://www.springer.com/978-3-642-53711-0
>> > http://amzn.com/3642537111
>> >
>> >
>> > Engineering Mechanics 3, Supplementary Problems: Dynamics
>> >
>> > http://www.amzn.com/B00SOXN8JU
>> >
>> >
>> > -----------------------------------------------
>> >
>> > <log_view.txt>
>>
>>
>
> --
> -----------------------------------------------
> Sanjay Govindjee, PhD, PE
> Professor of Civil Engineering
>
> 779 Davis Hall
> University of California
> Berkeley, CA 94720-1710
>
> Voice:  +1 510 642 6060
> FAX:    +1 510 643 5264s_g at berkeley.eduhttp://www.ce.berkeley.edu/~sanjay
> -----------------------------------------------
>
> Books:
>
> Engineering Mechanics of Deformable
> Solids: A Presentation with Exerciseshttp://www.oup.com/us/catalog/general/subject/Physics/MaterialsScience/?view=usa&ci=9780199651641http://ukcatalogue.oup.com/product/9780199651641.dohttp://amzn.com/0199651647
>
> Engineering Mechanics 3 (Dynamics) 2nd Editionhttp://www.springer.com/978-3-642-53711-0http://amzn.com/3642537111
>
> Engineering Mechanics 3, Supplementary Problems: Dynamics http://www.amzn.com/B00SOXN8JU
>
> -----------------------------------------------
>
>
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