Matthew Knepley emailed the following on 16/02/12 13:46: > On Thu, Feb 16, 2012 at 7:43 AM, Gerard Gorman > <g.gorman at imperial.ac.uk <mailto:g.gorman at imperial.ac.uk>> wrote: > > Matthew Knepley emailed the following on 16/02/12 13:29: >> On Thu, Feb 16, 2012 at 3:38 AM, Mohammad Mirzadeh >> <mirzadeh at gmail.com <mailto:mirzadeh at gmail.com> >> <mailto:mirzadeh at gmail.com <mailto:mirzadeh at gmail.com>>> wrote: >> >> Hi guys, >> >> I'm wondering if there is any implementation for >> ParMETIS_V3_PartGeomKway()? All I can find is the implementation >> for ParMETIS_V3_PartKway and I'm wondering if including the vertex >> positions could help me get a better partitioning? >> >> >> As far as communication goes, it will not help. >> >> >> Also I have a general question. Is minimizing number of edge cuts >> essentially the same as minimizing communication? I understand that >> they are related, but communication is proportional to the number >> of ghost points which is not exactly equal (its actually less than) >> to the number of edge cuts. So then is it possible that this could >> actually result in larger number of ghost points, at least for some >> of processors? >> >> >> It of course depends on your problem and the graph you draw, but >> you can always draw a graph where the edge cut is exactly your >> communication. >> >> > > > It might also be interesting to look at Zoltan's hypergraph > partitioning which can better balance communications - > http://www.cs.sandia.gov/zoltan/dev_html/dev_phg.html > > > I would caution you that one thing people are rarely careful about is > quantifying the effect of latency vs communication volume. I would > bet you $10 that the lion's share of slow down is due to load > imbalance/latency rather than communication volume (since comm links > are so big). > > Matt >
I believe you'd be correct in the vast majority of cases. Anyhow, as Daniel Bernstein says, "Profile. Don't speculate." Cheers Gerard
