[petsc-users] ParMETIS_V3_PartGeomKway

[Matthew Knepley]

On Thu, Feb 16, 2012 at 7:43 AM, Gerard Gorman <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>> 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


>
> Cheers
> Gerard
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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