On 12/09/2014 12:24 PM, Ralph Castain wrote:
Can you provide an example cmd line you use to launch one of these tests using
1.8.3? Some of the options changed between the 1.6 and 1.8 series, and we bind
by default in 1.8 - the combination may be causing you a problem.
I very simply launch:
"mpirun -np 32 myprog"
Maybe the result of "-mca mpi_show_mca_params all" would be insightful?
Eric
On Dec 9, 2014, at 9:14 AM, Eric Chamberland <eric.chamberl...@giref.ulaval.ca>
wrote:
Hi,
we were used to do oversubscribing just to do code validation in nightly
automated parallel runs of our code.
I just compiled openmpi 1.8.3 and launched the whole suit of
sequential/parallel tests and noticed a *major* slowdown in oversubscribed
parallel tests with 1.8.3 compared to 1.6.5.
For example, on my computer (2 cpu), a validation test of 64 processes launched
with 1.8.3 took 1500 seconds (~29 minutes) to execute, while the very same test
compiled with 1.6.5 took only 7.4 seconds!
To have this result with 1.6.5 we had to set the variable
"OMPI_MCA_mpi_yield_when_idle=1", but it seems to have no effects in 1.8.3 when I launch
more processes than number of core in my computer, even if it is still mentioned to work (see
http://www.open-mpi.org/faq/?category=running#force-aggressive-degraded). However, when I launch
with fewer processes than number of core, then it is faster without
"OMPI_MCA_mpi_yield_when_idle=1", which is the same behavior in 1.6.5.
I tried to launch with a host file like this:
localhost slots=2
but it changed nothing...
What do I do wrong?
Is it possible to retrieve "performances" of 1.6.5 for oversubscription?
Is there a compilation option that I have to enable in 1.8.3?
Here are the config.log and "ompi_info --all" files for both versions of mpi:
http://www.giref.ulaval.ca/~ericc/ompi_bug/config.165.log.gz
http://www.giref.ulaval.ca/~ericc/ompi_bug/config.183.log.gz
http://www.giref.ulaval.ca/~ericc/ompi_bug/ompi_info.all.165.txt.gz
http://www.giref.ulaval.ca/~ericc/ompi_bug/ompi_info.all.183.txt.gz
Thanks,
Eric
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