[Beowulf] Re: MPI Implementations for SMP use

Isaac Dooley idooley2 at uiuc.edu
Sun Dec 19 15:37:20 PST 2004

>>You would think that, but the nice thing about pure MPI is that
>>locality is perfect. So in most cases, a pure MPI code beats a hybrid
>>code. That's good, because hybrid programming is more complicated than
>>straight MPI or straight OpenMP.
Not necessarily. Charm++ uses an abstraction that does not concern the 
programmer with the location/node of a given object. Hence it is not 
more complicated than straight MPI. Its AMPI(an adaptive MPI 
implementation) works the same way, and both are free. 
(http://charm.cs.uiuc.edu). There are some papers at the site on this 
topic. Also locality may be an issue for some, but as we all know, 
applications have different bottlenecks and issues. Locality may be 
usefull for small programs which fit in cache. However there are many 
real applications which have network bottlenecks, IO bottlenecks or 
other problems which make the CPU and/or memory locality not the 
bottleneck. Maybe I'm just misunderstanding your reference to locality 


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