In reply to Fab.

I amorphously referred to this in slide 23: "What are the arguments to SESSION_CREATE?" I think I said during the talk that I assumed that there would have to be a string or integer tag argument so that multiple threads invoking SESSION_CREATE concurrently could be done safely (i.e., they could match their peers in other processes and create a unique communicator safely).

If you don't do something like this, having only a single session wouldn't be super-useful -- it would be effectively the same as the current INIT / FINALIZE scheme.