[Beowulf] multi-threading vs. MPI

Brian D. Ropers-Huilman brian.ropers.huilman at gmail.com
Fri Dec 7 13:24:34 PST 2007

On Dec 7, 2007 2:41 PM, Toon Knapen <toon.knapen at gmail.com> wrote:
> Greg Lindahl wrote:
> >
> > In real life (i.e. not HPC), everyone uses message passing between
> > nodes.  So I don't see what you're getting at.
> Many on this list suggest that using multiple MPI-processes on one and
> the same node is superior to MT approaches IIUC. However I have the
> impression that almost the whole industry is looking into MT to benefit
> from multi-core without even considering message-passing. Why is that so?

Because most of the "real" world does everything in a single node.
Given multi-cores, they have to move down the MT path.

The complications and effort of mixing MT on a node with the MP
between nodes -- absolutely required in our world -- is seen as too
great compared with the performance benefit. Simply staying with
multiple MP tasks, whether they are between nodes or within a node, is
much simpler -- it's what we already do.

No, the question of whether MP as we currently do it will scale to
larger and larger systems remains to be seen, but that's another

Brian D. Ropers-Huilman, Director
Systems Administration and Technical Operations
Minnesota Supercomputing Institute                 <bropers at msi.umn.edu>
599 Walter Library                                   +1 612-626-5948 (V)
117 Pleasant Street S.E.                             +1 612-624-8861 (F)
University of Minnesota                               Twin Cities Campus
Minneapolis, MN 55455-0255                       http://www.msi.umn.edu/

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