On single parameter characterization of parallelism

Issues pertinent to performance analysis of massively parallel systems are discussed. Attention is focused on the average parallelism of a software structure, which has been proposed as a single-parameter characterization of parallel software. It is argued that single-parameter characterization of parallel software or of parallel hardware rarely provides insight into the complex interactions among the software and hardware components of a parallel system. In particular, bounds for the speedup based on simple models of parallelism are violated when a model ignores the effects of communication delays.<
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