On Wed, May 30, 2012 at 7:20 PM, Jozsef Bakosi <jbakosi at lanl.gov> wrote:
> Hello, > > I have a mesh with very small cell sizes and in a Poisson equation CG solve > with ML preconditioner I get the following error: > > [31]PETSC ERROR: --------------------- Error Message > ------------------------------------ > [31]PETSC ERROR: Detected zero pivot in LU factorization see > > http://www.mcs.anl.gov/petsc/petsc-as/documentation/troubleshooting.html#ZeroPivot > ! > [31]PETSC ERROR: Zero pivot row 537 value 9.41111e-13 tolerance 1e-12! > > I really would like PETSc to NOT treat matrix values lower than 1e-12 to > be zero, so I'm trying to set the zero pivot to a lower value with > PCFactorSetZeroPivot(), but I still get the same error message: as if > the function call would have no effect. I also tried setting the > zeropivot via PetscOptionsSetValue("-pc_factor_zeropivot", ...), but > still no luck. > > Is there another way to set the zero pivot that I'm not aware of? > 1) Always look at -ksp_view 2) I bet this is a subsolve, so that it would be -sub_pc_factor_zeropivot <value>. You can verify by looking at -ksp_view > Is there a way to query the zero pivot value? > 3) Its printed out, 1.0e-12 Matt > Thanks, > J > -- > Jozsef Bakosi > Computational Physics Group (CCS-2) > MS T006, Los Alamos National Laboratory > Los Alamos, NM 87545, USA > email: jbakosi at lanl.gov > work: 505-663-5607 > fax : 505-663-5504 > -- 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/20120530/f2e2bcc4/attachment-0001.html>
