Shared memory programming in metacomputing environments: The global array approach

The performance of the Global Array shared-memory nonuniform memory-access programming model is explored in a wide-area-network (WAN) distributed supercomputer environment. The Global Array model is extended by introducing a concept of mirrored arrays that thanks to the caching and user-controlled consistency of the shared data structure scan reduce the application sensitivity to the network latency. Latencies and bandwidths for remote memory access are studied, and the performance of a large application from computational chemistry is evaluated using both fully distributed and also mirrored arrays. Excellent performance can be obtained with mirroring if even modest (0.5 MB/s) network bandwidth is available.