Not for that many procs - we default to binding to socket for anything more than 2 procs
> On Dec 9, 2014, at 9:24 AM, Nathan Hjelm <hje...@lanl.gov> wrote: > > > One thing that changed between 1.6 and 1.8 is the default binding > policy. Open MPI 1.6 did not bind by default but 1.8 binds to core. You > can unset the binding policy by adding --bind-to none. > > -Nathan Hjelm > HPC-5, LANL > > On Tue, Dec 09, 2014 at 12:14:32PM -0500, Eric Chamberland 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 >> >> >> >> >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users >> Link to this post: >> http://www.open-mpi.org/community/lists/users/2014/12/25936.php > _______________________________________________ > users mailing list > us...@open-mpi.org > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users > Link to this post: > http://www.open-mpi.org/community/lists/users/2014/12/25937.php
