It's easy to experiment, but I don't think it pays off. On May 25, 2012 8:41 AM, "Mark F. Adams" <mark.adams at columbia.edu> wrote:
> I like to compartmetnalize: deal with the math and computer science > separately. > > And you (or someone) decided to only do one comm for SSOR. You could, and > maybe should, communicate between SOR steps. > > On May 25, 2012, at 9:33 AM, Jed Brown wrote: > > Fair point for large subdomains, but two additive have two comm steps > instead of one. > On May 25, 2012 8:24 AM, "Mark F. Adams" <mark.adams at columbia.edu> wrote: > >> >> On May 25, 2012, at 8:59 AM, Jed Brown wrote: >> >> On Fri, May 25, 2012 at 1:07 AM, Mark F. Adams <mark.adams at >> columbia.edu>wrote: >> >>> And, I've never seen Gauss-Siedel used with Cheby because G-S has the >>> correct damping properties, as is, for the Laplacian. >>> >> >> The point is to have something adequate for things that are not >> Laplacians. I tried running SOR without Cheby, but it was far less robust. >> >> So I know it looks funny, but I don't have a similarly robust >> alternative. If we are living in a world where local work is cheap, we >> might as well do local SOR instead of pbjacobi. (Note that Cheby+pbjacobi >> is nearly as good as Cheby+SOR in some cases, but much worse in others.) >> >> >>> Note, G-S is not symmetric and Cheby for unsymmetric is a different can >>> of worms. So if A is symmetric then maybe try SSOR. >>> >> >> The default SOR is local_symmetric. >> >> >> So it does a forward and backward pass. So it is really two smoothing >> steps. One should compare it with two additive smoothers. >> >> > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20120525/267fd582/attachment.html>