On Tue, Jun 8, 2010 at 12:33 AM, Andreas Hauffe < andreas.hauffe at tu-dresden.de> wrote:
> Dear all, > > I want to solve a linear System with a symmetric positive definite matrix. > I > use the external package MUMPS as solver with the following commands > > call KSPCreate(PETSC_COMM_WORLD,ksp,ierr) > call KSPSetOperators(ksp,mat,mat,DIFFERENT_NONZERO_PATTERN,ierr) > call KSPSetType(ksp,KSPPREONLY,ierr) > call KSPGetPC(ksp,prec,ierr) > call PCSetType(prec,PCCHOLESKY,ierr) > call PCFactorSetMatSolverPackage(prec,MAT_SOLVER_MUMPS,ierr) > call KSPSetFromOptions(ksp,ierr) > call KSPSolve(ksp,vec1,vec2,ierr) > > and give the option "-mat_mumps_sym 1" (symmetric positive definite). > > If I run the program with one MPI-process everything works fine. For a low > number of unknows it also works for more MPI-processes. If I increase the > number of unknows (>50000) and use more then one MPI-process on one or more > host, I get a MUMPS error that the matrix is singular. With one MPI-process > everything is still fine. The critical value for the number of unknows > depends also on the use of the debug-version or non-debug-version of PETSc. > If I do not use the option "-mat_mumps_sym 1" everything also works. > It sounds like your matrix is not actually symmetric on multiple processes: http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/Mat/MatIsSymmetric.html Matt > Right now the finite element assembling process (MatSetValue) is only done > with rank 0. So the hole matrix gets all its values only from rank 0. > > Could someone explain this behaviour? Where is my error? > > Btw, I am currently using PETSc 3.0 since I work with SLEPc as well. > > Thank you very much, > -- > Andreas Hauffe > > > ---------------------------------------------------------------------------------------------------- > Technische Universit?t Dresden > Institut f?r Luft- und Raumfahrttechnik / Institute of Aerospace > Engineering > Lehrstuhl f?r Luftfahrzeugtechnik / Chair of Aircraft Engineering > > D-01062 Dresden > Germany > > phone : (++49)351 463 38496 > fax : (++49)351 463 37263 > mail : andreas.hauffe at tu-dresden.de > Website : http://tu-dresden.de/mw/ilr/lft > > ---------------------------------------------------------------------------------------------------- > -- 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/20100608/3b89da52/attachment.htm>
