[petsc-users] Any suggestion for this kinds of matrix?

[Bao Kai]

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 )

[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
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