Operated by Universities Space Research Association

Interprocessor communication overhead is a crucial measure of the power of parallel computing systems—its impact can severely limit the performance of parallel programs. This report presents measurements of communication overhead on three contemporary commercial mul-ticomputer systems: the Intel Paragon, the IBM SP2 and the Meiko CS-2. In each case the time to communicate between processors is presented as a function of message length. The time for global syn-chronization and memory access is discussed. The performance of these machines in emulating hypercubes and executing random pair-wise exchanges is also investigated. It is shown that the interprocessor communication time depends heavily on the specific communication pattern required. These obser-vations contradict the commonly held belief that communication over-head on contemporary machines is independent of the placement of tasks on processors. The information presented in this report permits the evaluation of the efficiency of parallel algorithm implementations against standard baselines