I understand that, but I'm trying to provide default behavior for the solver
because the default one (no parameters) works very bad in my case.
However, I'm stuck because I can't set the same parameters that I obtain with
command line arguments "-pc_type asm -sub_pc_type lu".
Can someone point me where is the error with the following code?
...
...
PetscInitialize(&argc, &argv,NULL,NULL);
PetscErrorCode ierr = MatCreate(PETSC_COMM_WORLD,&A_);CHKERR(ierr);
// create linear solver context
ierr = KSPCreate(PETSC_COMM_WORLD,&ksp_);CHKERR(ierr);
// initial nonzero guess
ierr = KSPSetInitialGuessNonzero(ksp_,PETSC_TRUE); CHKERR(ierr);
// set runtime options
ierr = KSPSetFromOptions(ksp_);CHKERR(ierr);
// set the default preconditioner for this program to be ASM
PC pc;
ierr = KSPGetPC(ksp_,&pc); CHKERR(ierr);
ierr = PCSetType(pc, PCASM); CHKERR(ierr);
KSP *subksp; /* array of KSP contexts for local
subblocks */
PetscInt nlocal,first; /* number of local subblocks, first local
subblock */
PC subpc; /* PC context for subblock */
/*
Call KSPSetUp() to set the block Jacobi data structures (including
creation of an internal KSP context for each block).
Note: KSPSetUp() MUST be called before PCASMGetSubKSP().
*/
ierr = KSPSetUp(ksp_);CHKERR(ierr);
/*
Extract the array of KSP contexts for the local blocks
*/
ierr = PCASMGetSubKSP(pc,&nlocal,&first,&subksp);CHKERR(ierr);
/*
Loop over the local blocks, setting various KSP options
for each block.
*/
for (int i=0; i<nlocal; i++) {
ierr = KSPGetPC(subksp[i],&subpc);CHKERR(ierr);
ierr = PCSetType(subpc,PCLU);CHKERR(ierr);
}
This is the error I get:
User explicitly sets subdomain solvers.
[0]PETSC ERROR: --------------------- Error Message
------------------------------------
[0]PETSC ERROR: Null argument, when expecting valid pointer!
[0]PETSC ERROR: Null Object: Parameter # 1!
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 3.1.0, Patch 7, Mon Dec 20 14:26:37 CST
2010
[0]PETSC ERROR: See docs/changes/index.html for recent updates.
[0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[0]PETSC ERROR: See docs/index.html for manual pages.
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: yafeq/a.out on a darwin10. named lsmspc26.epfl.ch by aaragon
Wed Apr 27 09:14:25 2011
[0]PETSC ERROR: Libraries linked from /Users/aaragon/Local/lib
[0]PETSC ERROR: Configure run at Thu Apr 7 17:01:26 2011
[0]PETSC ERROR: Configure options --prefix=/Users/aaragon/Local
--with-mpi-include=/Users/aaragon/Local/include
--with-mpi-lib=/Users/aaragon/Local/lib/libmpich.a --with-superlu=1
--with-superlu-include=/Users/aaragon/Local/include/superlu
--with-superlu-lib=/Users/aaragon/Local/lib/libsuperlu.a --with-superlu_dist=1
--with-superlu_dist-include=/Users/aaragon/Local/include/superlu_dist
--with-superlu_dist-lib=/Users/aaragon/Local/lib/libsuperlu_dist.a
--with-parmetis=1 --download-parmetis=ifneeded
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: MatGetVecs() line 7265 in src/mat/interface/matrix.c
[0]PETSC ERROR: KSPGetVecs() line 806 in src/ksp/ksp/interface/iterativ.c
[0]PETSC ERROR: KSPSetUp_GMRES() line 94 in src/ksp/ksp/impls/gmres/gmres.c
[0]PETSC ERROR: KSPSetUp() line 199 in src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: User provided function() line 397 in
"unknowndirectory/"/Users/aaragon/Local/include/cpputils/solver.hpp
[0]PETSC ERROR: --------------------- Error Message
------------------------------------
[0]PETSC ERROR: Operation done in wrong order!
[0]PETSC ERROR: Need to call PCSetUP() on PC (or KSPSetUp() on the outer KSP
object) before calling here!
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 3.1.0, Patch 7, Mon Dec 20 14:26:37 CST
2010
[0]PETSC ERROR: See docs/changes/index.html for recent updates.
[0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[0]PETSC ERROR: See docs/index.html for manual pages.
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: yafeq/a.out on a darwin10. named lsmspc26.epfl.ch by aaragon
Wed Apr 27 09:14:25 2011
[0]PETSC ERROR: Libraries linked from /Users/aaragon/Local/lib
[0]PETSC ERROR: Configure run at Thu Apr 7 17:01:26 2011
[0]PETSC ERROR: Configure options --prefix=/Users/aaragon/Local
--with-mpi-include=/Users/aaragon/Local/include
--with-mpi-lib=/Users/aaragon/Local/lib/libmpich.a --with-superlu=1
--with-superlu-include=/Users/aaragon/Local/include/superlu
--with-superlu-lib=/Users/aaragon/Local/lib/libsuperlu.a --with-superlu_dist=1
--with-superlu_dist-include=/Users/aaragon/Local/include/superlu_dist
--with-superlu_dist-lib=/Users/aaragon/Local/lib/libsuperlu_dist.a
--with-parmetis=1 --download-parmetis=ifneeded
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: PCASMGetSubKSP_ASM() line 644 in src/ksp/pc/impls/asm/asm.c
[0]PETSC ERROR: PCASMGetSubKSP() line 926 in src/ksp/pc/impls/asm/asm.c
[0]PETSC ERROR: User provided function() line 402 in
"unknowndirectory/"/Users/aaragon/Local/include/cpputils/solver.hpp
[0]PETSC ERROR: --------------------- Error Message
------------------------------------
[0]PETSC ERROR: Invalid argument!
[0]PETSC ERROR: Wrong type of object: Parameter # 1!
[0]PETSC ERROR:
------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 3.1.0, Patch 7, Mon Dec 20 14:26:37 CST
2010
and the error continues...
On Apr 26, 2011, at 5:26 PM, Matthew Knepley wrote:
> 2011/4/26 Alejandro Marcos Arag?n <alejandro.aragon at gmail.com>
> Thank you Barry, your suggestion really helped speed up the program. The
> maximum number of iterations is 48. I still don't know what the asm
> pre-conditioner is but I guess I just need to read the manual. I'm trying to
> add code to do what you suggested automatically, and I found that I can add:
>
> PC pc;
> ierr = KSPGetPC(ksp_,&pc); CHKERR(ierr);
> ierr = PCSetType(pc, PCASM); CHKERR(ierr);
>
> However, I cannot find the function to replace the -sub_pc_type. Can you
> point me where to look? My system may not be symmetric so I can't use the cg
> option.
>
> 1) Hard coding it in your program does not make sense. You gain nothing, and
> lose a lot of flexibility.
>
> 2) You can do this using
>
>
> http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/PC/PCASMGetSubKSP.html
>
> Matt
>
> Thanks again for your response.
>
> a?
>
>
> On Apr 26, 2011, at 2:23 PM, Barry Smith wrote:
>
>>
>>> System solved in 3664 iterations... 42.683 s
>>
>> The preconditioner is simply not up to the task it has been assigned.
>> This number of iterations is problematic.
>>
>> Have you tried -pc_type asm -sub_pc_type lu If that works well you
>> can try -pc_type asm -sub_pc_type ilu and see if that still works.
>>
>> If the matrix is indeed symmetric positive definite you will want to use
>> -ksp_type cg
>>
>>
>>
>> Barry
>>
>>
>> On Apr 26, 2011, at 1:37 AM, Alejandro Marcos Arag?n wrote:
>>
>>> Hi all,
>>>
>>> I'm using the standard configuration of the KSP solver, but the time it
>>> takes to solve a large system of equations is increasing (because of the
>>> increasing number of iterations?). These are my timing lines and the log
>>> from the KSP solver in two consecutive solves:
>>>
>>> [1] Solving system... 0.154203 s
>>>
>>> KSP Object:
>>> type: gmres
>>> GMRES: restart=30, using Classical (unmodified) Gram-Schmidt
>>> Orthogonalization with no iterative refinement
>>> GMRES: happy breakdown tolerance 1e-30
>>> maximum iterations=10000
>>> tolerances: relative=1e-05, absolute=1e-50, divergence=10000
>>> left preconditioning
>>> using nonzero initial guess
>>> using PRECONDITIONED norm type for convergence test
>>> PC Object:
>>> type: bjacobi
>>> block Jacobi: number of blocks = 3
>>> Local solve is same for all blocks, in the following KSP and PC objects:
>>> KSP Object:(sub_)
>>> type: preonly
>>> maximum iterations=10000, initial guess is zero
>>> tolerances: relative=1e-05, absolute=1e-50, divergence=10000
>>> left preconditioning
>>> using PRECONDITIONED norm type for convergence test
>>> PC Object:(sub_)
>>> type: ilu
>>> ILU: out-of-place factorization
>>> 0 levels of fill
>>> tolerance for zero pivot 1e-12
>>> using diagonal shift to prevent zero pivot
>>> matrix ordering: natural
>>> factor fill ratio given 1, needed 1
>>> Factored matrix follows:
>>> Matrix Object:
>>> type=seqaij, rows=2020, cols=2020
>>> package used to perform factorization: petsc
>>> total: nonzeros=119396, allocated nonzeros=163620
>>> using I-node routines: found 676 nodes, limit used is 5
>>> linear system matrix = precond matrix:
>>> Matrix Object:
>>> type=seqaij, rows=2020, cols=2020
>>> total: nonzeros=119396, allocated nonzeros=163620
>>> using I-node routines: found 676 nodes, limit used is 5
>>> linear system matrix = precond matrix:
>>> Matrix Object:
>>> type=mpiaij, rows=6058, cols=6058
>>> total: nonzeros=365026, allocated nonzeros=509941
>>> using I-node (on process 0) routines: found 676 nodes, limit used is 5
>>>
>>>
>>> [1] System solved in 51 iterations... 0.543215 s
>>> ...
>>> ...
>>> ...
>>>
>>> [1] Solving system... 0.302414 s
>>>
>>> KSP Object:
>>> type: gmres
>>> GMRES: restart=30, using Classical (unmodified) Gram-Schmidt
>>> Orthogonalization with no iterative refinement
>>> GMRES: happy breakdown tolerance 1e-30
>>> maximum iterations=10000
>>> tolerances: relative=1e-05, absolute=1e-50, divergence=10000
>>> left preconditioning
>>> using nonzero initial guess
>>> using PRECONDITIONED norm type for convergence test
>>> PC Object:
>>> type: bjacobi
>>> block Jacobi: number of blocks = 3
>>> Local solve is same for all blocks, in the following KSP and PC objects:
>>> KSP Object:(sub_)
>>> type: preonly
>>> maximum iterations=10000, initial guess is zero
>>> tolerances: relative=1e-05, absolute=1e-50, divergence=10000
>>> left preconditioning
>>> using PRECONDITIONED norm type for convergence test
>>> PC Object:(sub_)
>>> type: ilu
>>> ILU: out-of-place factorization
>>> 0 levels of fill
>>> tolerance for zero pivot 1e-12
>>> using diagonal shift to prevent zero pivot
>>> matrix ordering: natural
>>> factor fill ratio given 1, needed 1
>>> Factored matrix follows:
>>> Matrix Object:
>>> type=seqaij, rows=2020, cols=2020
>>> package used to perform factorization: petsc
>>> total: nonzeros=119396, allocated nonzeros=163620
>>> using I-node routines: found 676 nodes, limit used is 5
>>> linear system matrix = precond matrix:
>>> Matrix Object:
>>> type=seqaij, rows=2020, cols=2020
>>> total: nonzeros=119396, allocated nonzeros=163620
>>> using I-node routines: found 676 nodes, limit used is 5
>>> linear system matrix = precond matrix:
>>> Matrix Object:
>>> type=mpiaij, rows=6058, cols=6058
>>> total: nonzeros=365026, allocated nonzeros=509941
>>> using I-node (on process 0) routines: found 676 nodes, limit used is 5
>>>
>>> [1] System solved in 3664 iterations... 42.683 s
>>>
>>>
>>>
>>> As you can see, the second iteration takes more than 40 seconds to solve.
>>> Could some explain why this is happening and why he number of iterations is
>>> increasing dramatically between solves? Thank you all,
>>>
>>> Alejandro M. Arag?n, Ph.D.
>>
>
>
>
>
> --
> What most experimenters take for granted before they begin their experiments
> is infinitely more interesting than any results to which their experiments
> lead.
> -- Norbert Wiener
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