Supercritical speedup

Abstract

The notions of the critical path of events and critical rime of an event are key concepts in analyzing the performance of a parallel discrete event simulation. The highest critical time of any event in a simulation is a lower bound on the time it takes to execute a simulation using any conservative simulation mechanism, and is also a lower bound on the time taken by some optimistic methods. However, at least one optimistic mechanismis able to beat the critical path bound in a nontrivial way. bounded by its length and when it is not. We show (again) that no conservative mechanism can beat the critical path bound, but we also show that at least four known optimistic mechanisms, Time Warp with lazy cancellation, Time Warp with lazy rollback, Time Warp with phase decomposition, and the Chandy-Sherman space-time family of mechanisms, all can do so. As a result, we say that those mechanisms are capable of super-