Bogdan,
Thanks for your quick response. I've learned quite a bit about LAM-MPI since I
sent my e-mail this morning and your reply has made me think a bit more deeply
about the problem/solution
For your information, it is only a small group of researchers who want to use
the process creation feature of MPI-2 and as such need something like LAM-MPI.
Our operational weather-forecasting model does not use this feature. So this
(and the majority of our codes) will continue to use IBM's (otherwise good) MPI
implementation.
We use IBM's "xlf95_r" compiler with the "-qsmp=omp" flag to multi-thread.
Basically we use MPI at a very high level in the code and then use OpenMP within
each of the MPI tasks. In this way we get much better scaling than using just MPI.
My understanding is that the codes that will need to use LAM-MPI do not use
OpenMP (but that could change, hence the query). Also, they won't be using all
the CPUs (maybe a couple of hundred, not thousands).
One possibility of getting over the "rsh" scalability problem could be to use
"poe" (which is already integrated with LoadLeveler) as the mechanism for
starting the LAM daemons:
e.g.
./configure --with-rsh="/usr/bin/poe"
though this would need to be tested. If this worked OK then we could add a few
simple commands in the LoadLeveler prolog and epilog scripts and LAM-MPI could
then be be said to be LoadLeveler-aware.
Thanks again for your reply.
Regards
Neil
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