[Swift-devel] Falkon and Coaster support for MPI

[Ben Clifford]

Do you really mean falkon and/or coaster or do you mean MPI jobs launched 
from Swift onto BG/P?

The implementation of the latter might be completely distinct from Coaster 
and or Falkon. It might be desired to run a specific MPI application on 
all cores in a particular processor set (or whatever they are called). In 
such a case, the per-node individual job management that falkon and 
coaster provide would be almost/entirely irrelevant.

I presume there is some existing mechanism for launching an MPI job on 
every core in a processor set already.

It might be that it would be more appropriate for Swift to cause that 
mechanism to be used, making 'one node' = 'one pset' rather than 'one 
node' = 'one cpu' (where node is the basic unit that can execute a job). 

There is a (substantially?) more complicated case of causing one pset to 
run multiple different MPI jobs simultaneously, with some cores going to 
one job, and some to another.

The above two are (from my perspective) very different use cases; any 
future discussion should clarify which one is being discussed, rather than 
being based the always-vague "I want to use MPI".

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