See https://www.open-mpi.org/faq/?category=tuning#setting-mca-params for a little more info on how to set MCA params.
In terms of physical vs. logical -- are you talking about hyperthreading? If so, Open MPI uses the number of *cores* (by default), because that's what "most" HPC users want (I put "most" in quotes because this can quickly turn into a religious debate -- the "cores vs. hyperthreads" discussion has come up on this list a few times over the years, and "most" HPC-related workloads still tend to benefit from using a whole core vs. a hyperthread). Regardless, you can have Open MPI use hyperthreads by default (instead of cores) with the mpirun option --use-hwthread-cpus. > On Jan 10, 2018, at 10:48 AM, r...@open-mpi.org wrote: > > Set the MCA param “rmaps_base_oversubscribe=1” in your default MCA param > file, or in your environment > >> On Jan 10, 2018, at 4:42 AM, Florian Lindner <mailingli...@xgm.de> wrote: >> >> Hello, >> >> a recent openmpi update on my Arch machine seems to have enabled >> --nooversubscribe, as described in the manpage. Since I >> regularly test on my laptop with just 2 physical cores, I want to set >> --oversubscribe by default. >> >> How can I do that? >> >> I am also a bit surprised, that openmpi takes the physical number of cores >> into account, not the logical (which is 4 on >> my machine). >> >> Thanks, >> Florian >> _______________________________________________ >> users mailing list >> users@lists.open-mpi.org >> https://lists.open-mpi.org/mailman/listinfo/users > > _______________________________________________ > users mailing list > users@lists.open-mpi.org > https://lists.open-mpi.org/mailman/listinfo/users -- Jeff Squyres jsquy...@cisco.com _______________________________________________ users mailing list users@lists.open-mpi.org https://lists.open-mpi.org/mailman/listinfo/users
