I believe the problem is that you are only applying the MCA
parameters to the first app context instead of all of them:

Thank you very much.. applying the parameters with -gmca works fine with the test case (and I'll try the actual one soon). However and this is minor since it works with method (1),...

There are two main ways of doing this:

2) Alternatively you can duplicate the MCA parameters for each app context:

.. This actually doesn't work. I had thought of that and tried it, and I still get the same connection problems. I just rechecked this again to be sure.

Again, many thanks for the help!

With best wishes,
- Brian

Brian Dobbins
Yale University HPC