[Beowulf] Using Autoparallel compilers or Multi-Threaded libraries with MPI

Mark Hahn hahn at mcmaster.ca
Fri Nov 30 18:21:53 EST 2007


> IMHO the hybris approach (MPI+threads) is interesting in case every
> MPI-process has lots of local data.

yes.  but does this happen a lot?  the appealing case would be 
threads that make lots of heavy use of some large data, _but_
without needing synchronization/locking.  once you need locking
among the threads, message passing starts to catch up.

> latter is simpler because it only requires MPI-parallelism but if the code
> is memory-bound and every mpi-process has much of the same data, it will be
> better to share this common data with all processes on the same cpu and thus
> use threads intra-node.

what kind of applications behave like that?  I agree that if your MPI 
app is keeping huge amounts of (static) data replicated in each rank,
you should rethink your design.

thanks, mark hahn.
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