2019.1 mpiexec worked as expected - mpiexec -np 2 -hosts A,B P issued one process P on each of hosts A and B.
2019.5 mpiexec -np 2 -hosts A,B -P issues two P's on A.
It's maddening because this is not how any other MPI I've experienced works...
mpiexec -configfile CF works the same in both releases. With this I can make things work, but it's very, VERY annoying.
Meanwhile, 2019.5 MPI_BCast() appears to be better behaved than 2019.1 MPI_BCast(). This is a good thing, and worth the upgrade.
I'm not in to spending 2-1/2 hours on each release to see if 2019.2 through 2019.4 might have better overall behavior.
2019.5 works as expected. it was an issue in 2019.1. By default ppn (processes per node) in Intel MPI is the number of the physical cores on the first node. If you want to run 1 process per node, please specify -ppn=1 option.
Note from the documentation:
-ppn sets the number of processes to launch on each node; if the option is not specified, processes are assigned to the physical cores on the first node; if the number of cores is exceeded, the next node is used
Best regards, Anatoliy