It isn't in a file - unless you specify it, OMPI will set it
automatically based on the number of procs on the node vs. what OMPI
thinks are the number of available processors. The question is: why
does OMPI not correctly know the number of processors on your machine?
I don't remember now, but did you send us this info:
http://www.open-mpi.org/community/help/
If not, could you please do so? It would help us track down the problem.
Thanks
Ralph
On Apr 7, 2009, at 2:16 PM, Steve Kargl wrote:
On Tue, Apr 07, 2009 at 01:40:13PM -0600, Ralph Castain wrote:
I would really suggest looking at George's note first as I think you
are chasing your tail here. It sounds like the most likely problem is
that OMPI thinks you are oversubscribed and is setting sched_yield
accordingly. which would fully account for these diffs.
Note that the methods for setting sched yield are different between
the various releases, so something could be catching you here. If you
are sure you aren't oversubscribing, then set -mca
mpi_yield_when_idle
0 on your cmd line to override any internal settings.
'-mca mpi_yield_when_idle 0' returns the performance of 1.3.1 to
that of 1.2.9. In fact, 1.3.1 may be marginally better. A comparison
can be see at
http://troutmask.apl.washington.edu/~kargl/ompi_cmp_yield.jpg
So, in what file is sched_yield set?
--
Steve
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