Ah, yes - so here is what is happening. When no slot info is provided, we use
the number of detected cores on each node as the #slots. So if you want to
loadbalance across the nodes, you need to set —map-by node
Or add slots=1 to each line of your host file to override the default behavior
> On
Here's my command:
/bin/mpirun --machinefile
hosts.dat -np 4
Here's my hosts.dat file:
% cat hosts.dat
node01
node02
node03
node04
All 4 ranks are launched on node01. I don't believe I've ever seen this
before. I had to do a sanity check, so I tried MVAPICH2-2.1a and got what I
expected:
