On Sat, Jul 16, 2011 at 16:11, Barry Smith <bsmith at mcs.anl.gov> wrote:
> > Jed, > > I just remembered something I should have said when we talked about the > rewrite of the KSPSPECEST stuff. > > If one has the bound on the smallest eigenvalue of the (preconditioned) > operator then ones convergence test can take that into account and know that > the 2-norm of the error of the linear solver (as opposed to the 2 norm of > the residual) is less than some tolerance. Of course the KSPSPECEST can give > us this information, even though Mark doesn't believe it is accurate enough > :-), with enough iterations it can be. I would expect it to become a good approximation when the KSP has converged on the low-frequency modes. I think Mark's objection is that a few iterations are usually nowhere near actually converging, so you can only use the estimate in a meaningful way to estimate the high end of the spectrum. > So ideally we'd have options that allowed convergence tests to use the > estimate of the error norm instead of just the residual norm. > How would you suggest handling restarts? -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20110716/200c8ca7/attachment.html>