In addition to what Gilles said, I usually advise users in ambiguous situations
to explicitly choose the transport. For example, you might want to explicitly
choose using the UCX PML:
mpirun --mca pil ucx ...
This way, you are 100% sure that Open MPI chose the UCX PML (if it can't choose
the
Raymond,
In the case of UCX, you can
mpirun --mca pml_base_verbose 10 ...
If the pml/ucx component is used, then your app will run over UCX.
If the pml/ob1 component is used, then you can
mpirun --mca btl_base_verbose 10 ...
btl/self should be used for communications to itself.
if btl/uct
