On Wed, May 30, 2012 at 3:16 PM, John Fettig <john.fettig at gmail.com> wrote:
> On Wed, May 30, 2012 at 3:04 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote: > > On Wed, May 30, 2012 at 1:58 PM, John Fettig <john.fettig at gmail.com> > wrote: > >> > >> I have a question about the difference between SAME_PRECONDITIONER and > >> DIFFERENT_NONZERO_PATTERN. If you solve multiple RHS's (with > >> different initial guesses) but the matrix does not change, should you > >> expect to get identical results with SAME_PRECONDITIONER and > >> DIFFERENT_NONZERO_PATTERN? > > > > > > Why are you even calling KSPSetOperators? Just call KSPSolve() for each > > right hand side. > > What I mean is if I run the code twice, once with SAME_PRECONDITIONER > and once with DIFFERENT_NONZERO_PATTERN, the solution for the second > solve in the code is different. I am sure the matrix does not change. > There are a couple of calls to MatZeroRows but I have verified that > the diagonal is set to the exact same value both time. The difference > in the solution is not insignificant (it is probably below the solver > tolerance but still in the 3rd significant digit). Is the initial residual the same. It would be helpful to see the -ksp_monitor_true_residual output Matt > > John > -- 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/20120530/9d25d491/attachment.html>
