If you have implemented hyperthreading by Enabling it in the BIOS, then when you look at
cat /proc/cpuinfo output, you will see 2x the # of CPUs than the number of cores on your system.
If that number of CPUs showing on a node = H, and the number of nodes in your cluster with this same configuration is M,
Then you can run your program on up to N = H x M MPI ranks,
and your Open MPI mpirun command can use the
‘-np N –npernode H’ options to indicate this.
Note that with some applications, you may see very little benefit to hyperthreading. In any case, you should also run on “-np N/2” ranks and add the “-npernode H/2” setting to not use more ranks per node than you have cores per node, and compare performance with N ranks (with H per node).
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