On Thu, Nov 10, 2011 at 1:48 PM, Bao Kai <paeanball at gmail.com> wrote:
> Dear all, > > I have been trying with PETSC to solve the linear system from mixed finite > element method. > > The pattern of the matrix is as the following, but due to the irregular > boundary involved, the matrix A is not strictly symmetric. > > A dt* C > > C^T 0 > > As a result of the matrix pattern, the diagonal entries of the > bottom-right portion are all zero. > > I am just wondering if there are any suggestion of the type of the solver > and preconditioner for this kinds of linear system? Thank you very much. > > When I tried to solve the system with PETSC, I got the following > information. ( PCType PCASM, KSPType, KSPFGMRES ) > ILU is jsut not going to work for this type of matrix (a saddle point). I suggest reading about PCFIELDSPLIT. Matt > [0]PETSC ERROR: --------------------- Error Message > ------------------------------------ > [0]PETSC ERROR: Object is in wrong state! > [0]PETSC ERROR: Matrix is missing diagonal entry 288398! > [0]PETSC ERROR: > ------------------------------------------------------------------------ > [0]PETSC ERROR: Petsc Release Version 3.2.0, Patch 4, Sun Oct 23 12:23:18 > CDT 2011 > [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: Libraries linked from > /home/baok/software/petsc-3.2-p4/arch-linux2-c-debug-withhypre/lib > [0]PETSC ERROR: Configure run at Thu Nov 10 11:49:03 2011 > [0]PETSC ERROR: Configure options --download-hypre=yes > [0]PETSC ERROR: > ------------------------------------------------------------------------ > [0]PETSC ERROR: MatILUFactorSymbolic_SeqAIJ_ilu0() line 1636 in > /home/baok/software/petsc-3.2-p4/src/mat/impls/aij/seq/aijfact.c > [0]PETSC ERROR: MatILUFactorSymbolic_SeqAIJ() line 1740 in > /home/baok/software/petsc-3.2-p4/src/mat/impls/aij/seq/aijfact.c > [0]PETSC ERROR: MatILUFactorSymbolic() line 6092 in > /home/baok/software/petsc-3.2-p4/src/mat/interface/matrix.c > [0]PETSC ERROR: PCSetUp_ILU() line 216 in > /home/baok/software/petsc-3.2-p4/src/ksp/pc/impls/factor/ilu/ilu.c > [0]PETSC ERROR: PCSetUp() line 819 in > /home/baok/software/petsc-3.2-p4/src/ksp/pc/interface/precon.c > [0]PETSC ERROR: KSPSetUp() line 260 in > /home/baok/software/petsc-3.2-p4/src/ksp/ksp/interface/itfunc.c > [0]PETSC ERROR: PCSetUpOnBlocks_ASM() line 339 in > /home/baok/software/petsc-3.2-p4/src/ksp/pc/impls/asm/asm.c > [0]PETSC ERROR: PCSetUpOnBlocks() line 852 in > /home/baok/software/petsc-3.2-p4/src/ksp/pc/interface/precon.c > [0]PETSC ERROR: KSPSetUpOnBlocks() line 154 in > /home/baok/software/petsc-3.2-p4/src/ksp/ksp/interface/itfunc.c > [0]PETSC ERROR: KSPSolve() line 380 in > /home/baok/software/petsc-3.2-p4/src/ksp/ksp/interface/itfunc.c > [0]PETSC ERROR: main() line 261 in src/ksp/ksp/examples/tutorials/ex78.c > > > Best Regards, > Kai > > -- 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20111110/2ea2b385/attachment-0001.htm>
