[petsc-users] Solving Poisson equation with multigrid

[Michele Rosso]

Using

-pc_type gamg -pc_mg_cycle_type v -pc_gamg_agg_nsmooths 1 
-mg_coarse_sub_pc_factor_shift_type NONZERO  -option_left -ksp_view

still produces the same error:

[0]PCSetData_AGG bs=1 MM=131072
[0]PETSC ERROR: --------------------- Error Message 
------------------------------------
[0]PETSC ERROR: Detected zero pivot in LU factorization:
see http://www.mcs.anl.gov/petsc/documentation/faq.html#ZeroPivot!
[0]PETSC ERROR: Zero pivot row 280 value 6.56964e-17 tolerance 2.22045e-14!
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 3.3.0, Patch 3, Wed Aug 29 
11:26:24 CDT 2012
[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: ./hit on a  named nid15363 by Unknown Fri May 24 
17:06:50 2013
[0]PETSC ERROR: Libraries linked from
[0]PETSC ERROR: Configure run at
[0]PETSC ERROR: Configure options
[0]PETSC ERROR: 
------------------------------------------------------------------------
[0]PETSC ERROR: MatPivotCheck_none() line 583 in 
src/mat/impls/aij/seq//ptmp/skelly/petsc/3.3.03/cray_interlagos_build/real/src/include/petsc-private/matimpl.h
[0]PETSC ERROR: MatPivotCheck() line 602 in 
src/mat/impls/aij/seq//ptmp/skelly/petsc/3.3.03/cray_interlagos_build/real/src/include/petsc-private/matimpl.h
[0]PETSC ERROR: MatLUFactorNumeric_SeqAIJ() line 585 in 
src/mat/impls/aij/seq/aijfact.c
[0]PETSC ERROR: MatLUFactorNumeric() line 2803 in src/mat/interface/matrix.c
[0]PETSC ERROR: PCSetUp_LU() line 160 in src/ksp/pc/impls/factor/lu/lu.c
[0]PETSC ERROR: PCSetUp() line 832 in src/ksp/pc/interface/precon.c
[0]PETSC ERROR: KSPSetUp() line 278 in src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: PCSetUpOnBlocks_BJacobi_Singleblock() line 715 in 
src/ksp/pc/impls/bjacobi/bjacobi.c
[0]PETSC ERROR: PCSetUpOnBlocks() line 865 in src/ksp/pc/interface/precon.c
[0]PETSC ERROR: KSPSetUpOnBlocks() line 154 in 
src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: KSPSolve() line 403 in src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: PCSetUpOnBlocks_BJacobi_Singleblock() line 715 in 
src/ksp/pc/impls/bjacobi/bjacobi.c
[0]PETSC ERROR: PCSetUpOnBlocks() line 865 in src/ksp/pc/interface/precon.c
[0]PETSC ERROR: KSPSetUpOnBlocks() line 154 in 
src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: KSPSolve() line 403 in src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: PCMGMCycle_Private() line 20 in src/ksp/pc/impls/mg/mg.c
[0]PETSC ERROR: PCMGMCycle_Private() line 49 in src/ksp/pc/impls/mg/mg.c
[0]PETSC ERROR: PCMGMCycle_Private() line 49 in src/ksp/pc/impls/mg/mg.c
[0]PETSC ERROR: PCMGMCycle_Private() line 49 in src/ksp/pc/impls/mg/mg.c
[0]PETSC ERROR: PCApply_MG() line 326 in src/ksp/pc/impls/mg/mg.c
[0]PETSC ERROR: PCApply() line 384 in src/ksp/pc/interface/precon.c
[0]PETSC ERROR: KSPSolve_CG() line 139 in src/ksp/ksp/impls/cg/cg.c
[0]PETSC ERROR: KSPSolve() line 446 in src/ksp/ksp/interface/itfunc.c

On 05/24/2013 02:51 PM, Jed Brown wrote:
> Michele Rosso <mrosso at uci.edu> writes:
>
>>>      With petsc-3.4 (which you should upgrade to), use
>>>      -mg_coarse_sub_pc_factor_shift_type NONZERO
> Actually, use this with petsc-3.3 also (and please upgrade to
> petsc-3.4).
>
> The option you were passing was not being used.
>

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