On Fri, Dec 23, 2011 at 7:14 PM, Mohamad M. Nasr-Azadani <mmnasr at gmail.com>wrote:
> Thank you guys, > What happens right now when I use GMRES is that it reaches the maximum > number of iterations I set, i.e. 1000 (which should not). I have set the > restart to 20 (and then increased it to 1000) but no luck. It never > converges. It sounds like your operator is singular. Matt > > On Fri, Dec 23, 2011 at 7:23 AM, Jed Brown <jedbrown at mcs.anl.gov> wrote: > >> On Fri, Dec 23, 2011 at 07:43, Matthew Knepley <knepley at gmail.com> wrote: >> >>> Even if you lose orthogonality, it will just stagnate since you always >>> have the solution >>> from the first few vectors. Likewise, I do not see how you can get an >>> diverging sequence >>> from restarting since you always have the last residual, you just >>> stagnate. >>> >> >> The true residual can grow even though the estimate of the preconditioned >> residual decreases monotonically. When you restart, you re-evaluate the >> actual residual, which might be much larger. >> > > -- 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/20111223/ace04d12/attachment.htm>
