[R-sig-hpc] Rmpi and cpu usage on slaves

Ross Boylan ross at biostat.ucsf.edu
Thu Apr 23 22:55:35 CEST 2009

On Wed, 2009-04-22 at 12:55 -0400, Sean Davis wrote:
> So, as Dirk suggested, the 100% CPU usage is thought to be a feature
> and not
> a bug.
As someone who just ran into this (the link to the thread was in the
earlier links), I looked into why OpenMPI worked that way.  I think a
fairer characterization is that responsiveness while running Open MPI is
a feature; the 100% CPU useage is just a side effect.  Fixing it is on
their todo list, but it's not a high priority because the fix is a bit
tricky and the useage scenario that strikes the developers as standard
reserves the CPUs for the job anyway.

I don't happen to fit that scenario, but I suspect the developers are
right in their judgement of typical use.

If you're concerned, a number of work-arounds or brittle fixes are in
the openmpi archives; the responses to my query
(http://www.open-mpi.org/community/lists/users/2009/04/9016.php) have
pointers to a couple of them.

Ross Boylan                                      wk:  (415) 514-8146
185 Berry St #5700                               ross at biostat.ucsf.edu
Dept of Epidemiology and Biostatistics           fax: (415) 514-8150
University of California, San Francisco
San Francisco, CA 94107-1739                     hm:  (415) 550-1062

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