<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>On Dec 23, 2011, at 10:53 AM, Jed Brown wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div class="gmail_quote">On Fri, Dec 23, 2011 at 09:50, Mark F. Adams <span dir="ltr"><<a href="mailto:mark.adams@columbia.edu">mark.adams@columbia.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex; position: static; z-index: auto; ">
Humm, my G-S in not in PETSc and it is perfectly scalable. It does have more complex communication patterns but they are O(1) in latency and bandwidth. I'm not sure I understand your description above.</blockquote></div>
<br><div>It was more like, here's something that perhaps we want to put in PETSc, what rich communication pattern does it use, such that, if provided, the implementation would be simple?</div>
</blockquote></div><br><div>There is the implementation in Prometheus that uses my C++ linked lists and hash tables. I would like to implement this with STLs. I also hack into MPIAIJ matrices to provide a primitive of applying G-S on an index set of local vertices, required for the algorithm. This should be rethought. I would guess that it would take about a week or two to move this into PETSc.</div><div><br></div><div>The complex communication required make this code work much better with large subdomains, so it is getting less attractive in a flat MPI mode, as it is currently written. If I do this I would like to think about doing it in the next programming model of PETSc (pthreads?). Anyway, this would take enough work that I'd like to think a bit about its design and even the algorithm in a non flat MPI model.</div><div><br></div><div>Note, I see the win with G-S over Cheby in highly unsymmetric (convection, hyperbolic) problems where Cheby is not very good.</div><div><br></div><div>Mark</div></body></html>