Analysing Probabilistically Constrained Optimism

In previous work we presented the DTRD algorithm, an optimistic synchronization algorithm for parallel discrete event simulation of multi-agent systems, and showed that it outperforms Time Warp and time windows on a range of test cases. DTRD uses a decision-theoretic model of rollback to derive an optimal time to delay read event so as to maximize the rate of LVT progression. The algorithm assumes that the inter-arrival times (both virtual and real) of events are normally distributed. In this paper we present a more detailed evaluation of the DTRD algorithm, and specifically how the performance of the algorithm is affected when the inter-arrival times do not follow the assumed distributions. Our analysis suggests that the performance of the algorithm is relatively insensitive to events whose inter-arrival times are not normally distributed. However, as the variance of event inter-arrival times increases, its performance degrades to that of Time Warp. The evaluation approach we present is generally applicable, and we sketch how a similar analysis may be performed for two other decision-theoretic optimistic synchronization algorithms. Copyright (C) 2009 John Wiley & Sons, Ltd