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Subject: Re: [OMPI devel] Affect of compression on modex and launch messages
From: Edgar Gabriel (gabriel_at_[hidden])
Date: 2008-04-04 14:52:03


actually, we used lzo a looong time ago with PACX-MPI, it was indeed
faster then zlib. Our findings at that time were however similar to what
George mentioned, namely a benefit from compression was only visible if
the network latency was really high (e.g. multiple ms)...

Thanks
Edgar

Roland Dreier wrote:
> > Based on some discussion on this list, I integrated a zlib-based compression
> > ability into ORTE. Since the launch message sent to the orteds and the modex
> > between the application procs are the only places where messages of any size
> > are sent, I only implemented compression for those two exchanges.
> >
> > I have found virtually no benefit to the compression. Essentially, the
> > overhead consumed in compression/decompressing the messages pretty much
> > balances out any transmission time differences. However, I could only test
> > this for 64 nodes, 8ppn, so perhaps there is some benefit at larger sizes.
>
> A faster compression library might change the balance... eg LZO
> (http://www.oberhumer.com/opensource/lzo) might be worth a look although
> I'm not an expert on all the compression libraries that are out there.
>
> - R.
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-- 
Edgar Gabriel
Assistant Professor
Parallel Software Technologies Lab      http://pstl.cs.uh.edu
Department of Computer Science          University of Houston
Philip G. Hoffman Hall, Room 524        Houston, TX-77204, USA
Tel: +1 (713) 743-3857                  Fax: +1 (713) 743-3335