semantics of collective collective, semantics of portabilitysafety collective, and portability collective, and deadlock
A correct, portable program must invoke collective communications so that deadlock will not occur, whether collective communications are synchronizing or not. The following examples illustrate dangerous use of collective routines.
Figure: A race condition causes non-deterministic matching of sends
and receives. One cannot rely on synchronization from a broadcast
to make the program deterministic.