Analysis of Optimistic Window-based Synchronization

This paper studies an analytic model of parallel discrete-event simulation, comparing the costs and bene ts of extending optimistic processing to the YAWNS synchronization protocol. The basic model makes standard assumptions about workload and routing; we develop methods for computing performance as a function of the degree of optimism allowed, overhead costs of state-saving, rollback, and barrier synchronization, and LP aggregation. This allows an approximation-based analysis of the range of situations under which optimism is a bene cial extension to YAWNS. We nd that limited optimism is bene cial if the processor load is sparse, but that aggregating LPs onto processors improves YAWNS relative performance. This work was supported by the National Aeronautics and Space Administration under NAS1-19480 while Dickens and Nicol were in residence at the Institute for Computer Applications in Science and Engineering (ICASE), NASA Langley Research Center, Hampton, VA 23681. Nicol's work was additionally supported by Carleton College while he was resident as a visiting research associate, and by NSF grant