Dear Matthew, PCFIELDSPLIT seems a little more complex, I will try that.
I tried some different preconditioners, only lu can get right results. With some pc, some wrong results can be obtained, such as the following one. tutorials]$ time ./ex78 -Ain A_in -rhs rhs -solu solu -noshift -pc_type hypre -pc_hypre_type parasails -ksp_gmres_restart 600 -ksp_rtol 1e-5 -ksp_typ gmres Read matrix in ascii format ... m: 288399, n: 288399, nz: 4023176 read A completed rowNumber[0] = 13 rowNumber[1] = 13 rowNumber[2] = 19 read A is complete ! Read rhs in ascii format ... Read exact solution in ascii format ... Accuracy of the reading data: | b - A*u |_2 : 3321.15 Iteration number is : 38 real 0m11.977s user 0m11.752s sys 0m0.216s The iteration should have converged, while converge to some wrong results. Regards, Kai Message: 8 > Date: Thu, 10 Nov 2011 14:10:14 +0000 > From: Matthew Knepley <knepley at gmail.com> > Subject: Re: [petsc-users] Any suggestion for this kinds of matrix? > To: PETSc users list <petsc-users at mcs.anl.gov> > Message-ID: > <CAMYG4GnxR2A+TcVzmsiOgD4wp4P+a_GRnPBg1YQKz7bJT5XiDw at mail.gmail.com > > > Content-Type: text/plain; charset="iso-8859-1" > > 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.htm > > > > ------------------------------ > > _______________________________________________ > petsc-users mailing list > petsc-users at mcs.anl.gov > https://lists.mcs.anl.gov/mailman/listinfo/petsc-users > > > End of petsc-users Digest, Vol 35, Issue 29 > ******************************************* > -------------- next part -------------- An HTML attachment was scrubbed... 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