RELATIONSHIPS BETWEEN REGULAR AND IRREGULAR COLLECTIVE COMMUNICATION OPERATIONS ON CLUSTERED MULTIPROCESSORS

Abstract

We characterize collective communication operations on (clustered) multiprocessor systems in terms of their communication volume, and arrive at useful relationships between regular and irregular operations over sets of processors and sets of cluster-nodes, respectively. We show that regular problems over sets of processors induce corresponding irregular problems over sets of nodes. We hereby identify a symmetric variant of the personalized all-to-all communication problem that might be worth studying in its own right, and discuss an algorithm for solving this problem. From a simple algorithm for the regular all-gather problem over sets of processors, we derive an algorithm for the irregular all-gather problem over both sets of processors and sets of nodes. For communication libraries like MPI, the relationships emphasize the need for efficient algorithms for the irregular collective communication operations.