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Ph.D. Theses

Why not change the past: Exploiting Lookback in Parallel Discrete Event Simulation

By Gang (Gilbert) Chen
Advisor: Boleslaw K. Szymanski
January 13, 2003

A component property named lookback, defined as the ability to change the past locally, will be discussed. Lookback enables a new class of PDES synchronization protocols, which unifies two previously known PDES techniques: out-of-timestamp order execution and local rollback. Lookback has proven to be more commonly present that lookahead, the basis for traditional conservative PDES synchronization protocols. Moreover, lookback-based protocols are shown to be capable of completing the simulation earlier than the limit imposed by the critical times of events, which is an insurmountable bound for traditional conservative protocols and optimistic protocols without optimization. Furthermore, there exist four types of lookback, referred to as direct strong lookback, universal strong lookback, direct weak lookback, and universal weak lookback. While strong lookback is required for lookback-based protocols, it has been demonstrated that all types of lookback can be exploited to improve the performance of optimistic protocols by reducing the number of rollbacks and anti-messages.

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