I’m trying to grok the problem, so bear with me a bit. It sounds like you have a machine with 12 physical cores, each with two hyperthreads, and you have HT turned on - correct?
If that is true, then the problem is that you are attempting to bind-to core (of which you have 12), but asking for 2 cpus/proc. Since you haven’t told us to use HTs as cpus, we are using “cores” as cpus - so this cmd is actually asking us to bind each process to 2 cores, resulting in an overload. So you have two options: * remove the cpus-per-proc directive. Since you are binding to core, we will automatically bind each process to both HTs in the core, which is the result you want * add the —use-hwthread-cpus flag and change your binding request to “hwthread". This will treat each HT as a separate cpu, and we will bind each process to 2 HTs, effectively binding them to the core. The revised manpage that hopefully helps explain this better is in the upcoming 1.8.4 release. I’m also working on a page for the web site to better explain the new map/rank/bind system. HTH Ralph > On Dec 5, 2014, at 12:55 AM, John Bray <jb...@allinea.com> wrote: > > To run a hybrid MPI/OpenMP code on a hyperthreaded machine with 24 virtual > cores, I've been using -n 12 --cpus-per-proc 2 so I can use OMP_NUM_THREADS=2 > > I now see that --cpus-per-proc is deprecated in favour of --map-by, but I've > been struggling to find a conversion as the --map-by documentation is not > very clear. > > What should I use to bind 2 virtual cores to each process? > > After I use -n 12 --cpus-per-proc 2 I get > > A request was made to bind to that would result in binding more > processes than cpus on a resource: > > Bind to: CORE > Node: mic1 > #processes: 2 > #cpus: 1 > > and suggests I need an override option > > But this doesn't to match my request for 2 cores per process, almost the > reverse, having 2 processes per core. I don't think I'm overloading my > virtual cores anyway > > John > _______________________________________________ > 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/2014/12/25917.php
