On Tue, Jul 10, 2012 at 3:29 PM, Paul T. Bauman <ptbauman at gmail.com> wrote:
> On Tue, Jul 10, 2012 at 1:34 PM, Paul T. Bauman <ptbauman at gmail.com>wrote: > >> Greetings, >> >> This question is somewhat related to this thread: >> http://lists.mcs.anl.gov/pipermail/petsc-users/2011-August/009583.html but >> instead of resurrecting that thread, I decided to start a new one. >> >> Summary: In the libMesh wrapper of PETSc's KSP, a call is made to >> KSPSetOperators; I gather this is in order to allow reusing the same >> preconditioner, if desired. However, I've noticed that when I use the >> following options, the sub-preconditioner type gets reset: >> >> -pc_type bjacobi -sub_pc_type ilu -sub_pc_factor_mat_solver_package >> superlu >> >> In particular, the first linear solve uses what I asked for, but in all >> following linear solves, the petsc ilu solver is used instead of superlu. >> If I remove the KSPSetOperators call, everything is peachy. >> >> My question: Does a call need to be made to PCSetFromOptions (or >> something similar...) to keep the superlu ilu solver around or would that >> wipe out the KSPSetOperators effect? Is this a PETSc bug? Other? >> > Thanks for your test case. Yes, this is a PETSc bug associated with handling of DIFFERENT_NONZERO_PATTERN. Fixed here and will be in the next patch release. http://petsc.cs.iit.edu/petsc/releases/petsc-3.3/rev/09d701958d66 We recommend that you only call KSPSetFromOptions (or PCSetFromOptions) once. > >> This is with petsc-3.3-p1. >> > > Sorry to reply to myself, but I read this and realized I was rather > imprecise. > > The KSPSetOperators call I referred to is in the solve step. In > particular, KSPSetFromOptions is called during initilization, only once, > but KSPSetOperators is called each time solve is called. I was able to > mimic my problem in the attached, slightly modified ksp/ex5.c, running with: > > mpiexec -np 6 ./ex5 -ksp_type gmres -pc_type bjacobi -sub_pc_type ilu > -ksp_view -ksp_monitor -sub_pc_factor_mat_solver_package superlu > -sub_pc_factor_levels 1 > > Is the correct solution just to call KSPSetFromOptions every time? Will > that be noticeable at all? I hope this was less vague than my original > message. Thanks again. > > Best, > > Paul > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120711/81bf2eff/attachment.html>
