Optimizing parallel applications for wide-area clusters

Recent developments in networking technology cause a growing interest in connecting local area clusters of workstations over wide area links, creating multilevel clusters, or metacomputers. Often, latency and bandwidth of local area and wide area networks differ by two orders of magnitude or more. One would expect only very coarse grain applications to achieve good performance. To test this intuition, we analyze the behavior of several existing medium-grain applications on a wide-area multicluster. We find that high performance can be obtained if the programs are optimized to take the multilevel network structure into account. The optimizations reduce intercluster traffic and hide intercluster latency, and substantially improve performance on wide area multiclusters. As a result, the range of metacomputing applications is larger than previously assumed