Yes, it isanecessarybutnotsufficientcondition.
At 2013-01-11 03:56:25,"Barry Smith" <bsmith at mcs.anl.gov> wrote: > > If cg says indefinite then it is indefinite > if cg runs and does not say it is indefinite it may still be indefinite > (though probably not all that likely). > > Barry > >On Jan 10, 2013, at 11:46 AM, Matthew Knepley <knepley at gmail.com> wrote: > >> On Thu, Jan 10, 2013 at 10:44 AM, w_ang_temp <w_ang_temp at 163.com> wrote: >> Hello, >> >> I want to determine the positive definiteness. So I want to know >> >> if it is a right way. >> >> I use "-ksp_type cg -pc_type none". You know, CG does not work for >> >> indefinite matrices. I get "Linear solve did not converge due to >> >> DIVERGED_INDEFINITE_MAT". From the information, I think it is indefinite. >> >> Is it a right way? >> >> >> Its not full proof, but it could be a diagnostic. >> >> Matt >> >> Thanks. >> >> Jim >> >> >> >> >> >> >> -- >> 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/20130112/3443c49c/attachment-0001.html>
