On Sat, Nov 24, 2012 at 1:14 PM, w_ang_temp <w_ang_temp at 163.com> wrote:
> Hello, > As is know, GMRES(m) is a very efficient solver when dealing with > symmetric indefinite > system. > If you use an SPD preconditioner, then MINRES is equivalent to full GMRES (without restarts), but uses a short recurrence. > And the restarted parameter *m* is critical. When the system is small, I > can do > several tests to find a suitable *m*. But when the system is very large, > it is very difficult > to do that. I read lots of papers about GMRES(*m*) and find that almost > none told the way to > get a suitable *m*. Someone told me that I can just choose the matrix > dimension as the *m*, but > I find that it is not right. > Using that restart makes GMRES just an inefficient way to compute a dense QR factorization, impractical unless the method converges much sooner. In practice, you choose the restart length to balance the cost of orthogonalizing and storage with the convergence rate. > So, generally, when using GMRES(*m*) as the sovler, how to use a > suitable restarted *m*? > Thanks. > Jim > > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20121124/812700d6/attachment.html>
