Compiler-directed Shared-Memory Communication for Iterative Parallel Applications

Many scientific applications are iterative and specify repetitive communication patterns. This paper shows how a parallel-language compiler and a predictive cache-coherence protocol in a distributed shared memory system together can implement shared-memory communication efficiently for applications with unpredictable but repetitive communication patterns. The compiler uses static analysis to identify program points where potentially repetitive communication occurs. At runtime, the protocol builds a communication schedule in one iteration and uses the schedule to pre-send data in subsequent iterations. This paper contains measurements of three iterative applications (including adaptive programs with unstructured data accesses) that show that a predictive protocol increases the number of shared-data requests satisfied locally, thus reducing the remote data access latency and total execution time.