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.
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. > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20111223/cfae4546/attachment.htm>
