Preventing deadlock with dynamic message scheduling

Although deadlock is not completely avoidable in distributed and parallel programming, we here describe theory and practice of a system that allows us to limit deadlock to situations in which there are true circular data dependences or failure of processes that compute data needed at other processes. This allows us to guarantee absence of deadlock in SPMD computations absent process failure. Our system guarantees optimal ordering of communication statements. We gratefully acknowledge the support of the US National Science Foundation under Award CISE EIA 9810708 without which this work would not have been possible.