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 <[email protected]
<mailto:[email protected]>> 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
<[email protected] <mailto:[email protected]>> 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 <tel:%2B1%20510%20642%206060>
> FAX: +1 510 643 5264 <tel:%2B1%20510%20643%205264>
>
> [email protected] <mailto:[email protected]>
> http://www.ce.berkeley.edu/~sanjay
<http://www.ce.berkeley.edu/%7Esanjay>
>
> -----------------------------------------------
>
> 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>
