PCNN preconditioner

[Andreas Grassl]

any suggestions?

cheers

ando

Andreas Grassl schrieb:
> Barry Smith schrieb:
>> Use MatCreateIS() to create the matrix. Use MatSetValuesLocal() to put
>> the values in the matrix
>> then use PCSetType(pc,PCNN); to set the preconditioner to NN.
>>
> 
> I followed your advice, but still run into problems.
> 
> my sourcecode:
> 
> ierr = KSPCreate(comm,&solver);CHKERRQ(ierr);
> ierr = KSPSetOperators(solver,A,A,DIFFERENT_NONZERO_PATTERN);CHKERRQ(ierr);
> ierr = KSPSetInitialGuessNonzero(solver,PETSC_TRUE);CHKERRQ(ierr);
> ierr = KSPGetPC(solver,&prec);CHKERRQ(ierr);
> ierr = PCSetType(prec,PCNN);CHKERRQ(ierr);
> //ierr = PCFactorSetShiftPd(prec,PETSC_TRUE);CHKERRQ(ierr);
> ierr = KSPSetUp(solver);CHKERRQ(ierr);
> ierr = KSPSolve(solver,B,X);CHKERRQ(ierr);
> 
> and the error message:
> 
> [0]PETSC ERROR: --------------------- Error Message
> ------------------------------------
> [0]PETSC ERROR: Detected zero pivot in LU factorization
> see
> http://www.mcs.anl.gov/petsc/petsc-as/documentation/troubleshooting.html#ZeroPivot!
> [0]PETSC ERROR: Zero pivot row 801 value 2.78624e-13 tolerance
> 4.28598e-12 * rowsum 4.28598!
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: Petsc Release Version 3.0.0, Patch 3, Fri Jan 30
> 17:55:56 CST 2009
> [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: Unknown Name on a linux64-g named mat1.uibk.ac.at by
> csae1801 Fri Feb 27 10:12:34 2009
> [0]PETSC ERROR: Libraries linked from
> /home/lux/csae1801/petsc/petsc-3.0.0-p3/linux64-gnu-c-debug/lib
> [0]PETSC ERROR: Configure run at Wed Feb 18 10:30:58 2009
> [0]PETSC ERROR: Configure options --with-64-bit-indices
> --with-scalar-type=real --with-precision=double --with-cc=icc
> --with-fc=ifort --with-cxx=icpc --with-shared=0 --with-mpi=1
> --download-mpich=ifneeded --with-scalapack=1
> --download-scalapack=ifneeded --download-f-blas-lapack=yes
> --with-blacs=1 --download-blacs=yes PETSC_ARCH=linux64-gnu-c-debug
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: MatLUFactorNumeric_Inode() line 1335 in
> src/mat/impls/aij/seq/inode.c
> [0]PETSC ERROR: MatLUFactorNumeric() line 2338 in src/mat/interface/matrix.c
> [0]PETSC ERROR: PCSetUp_LU() line 222 in src/ksp/pc/impls/factor/lu/lu.c
> [0]PETSC ERROR: PCSetUp() line 794 in src/ksp/pc/interface/precon.c
> [0]PETSC ERROR: KSPSetUp() line 237 in src/ksp/ksp/interface/itfunc.c
> [0]PETSC ERROR: PCISSetUp() line 137 in src/ksp/pc/impls/is/pcis.c
> [0]PETSC ERROR: PCSetUp_NN() line 28 in src/ksp/pc/impls/is/nn/nn.c
> [0]PETSC ERROR: PCSetUp() line 794 in src/ksp/pc/interface/precon.c
> [0]PETSC ERROR: KSPSetUp() line 237 in src/ksp/ksp/interface/itfunc.c
> [0]PETSC ERROR: User provided function() line 1274 in petscsolver.c
> 
> 
> Running PCFactorSetShift doesn't affect the output.
> 
> any ideas?
> 
> cheers
> 
> ando
> 

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