On Tue, Sep 15, 2009 at 6:04 PM, Ryan Yan <vyan2000 at gmail.com> wrote:
> Thanks Jed. > > And in the term ||Ae||/||Ax||, PETSc impilictly assume that we use zero as > initial guess and here the x really means exact solution, right? > This has nothing to do with the initial guess. Ae is the residual, and x is the current guess. We do not have the exact solution, but I guess A x^* = b, so that could have been used. Matt > > Yan > > > > > On Tue, Sep 15, 2009 at 6:41 PM, Jed Brown <jed at 59a2.org> wrote: > >> Ryan Yan wrote: >> > But can you say a little more about what happened in the first scenario, >> I >> > did not quite fellow you. Let's say, If I set -ksp_rtol 1e-2, what does >> this >> > mean in the left PC case. More specifically, which term will be >> considered >> > as a stop creteria for the KSP solve. >> >> Look at the first column (preconditioned residual norm). Notice that >> this is decreasing by 1e-2 and 1e-3 respectively in your examples. >> >> Jed >> >> > -- 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/20090915/9b3f3d55/attachment.htm>
