[Beowulf] multi-threading vs. MPI

Geoff Jacobs gdjacobs at gmail.com
Sat Dec 8 12:25:19 EST 2007


Toon Knapen 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.

I'm not sure where this conclusion came from.

> 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?
> 
> toon

These are developers working on NUMA and SMA, not network distributed
parallel processing. Different problem, different tool.

If an application is going to be using only shared memory, I have no
doubt the consensus here is to use native threads or OpenMP. If the
application is going to be working over a network, MPI (or PVM) is the
way to go.

Don't misconstrue any strategies and opinions on this list to be
generalizable to all types of parallel computing. This list is here to
discuss the engineering of Beowulf style systems, so opinions (unless
qualified) will generally apply to Beowulf computers as well.

-- 
Geoffrey D. Jacobs

To have no errors
  would be life without meaning
  No struggle, no joy
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