Virtual Time III, Part 2: Combining Conservative and Optimistic Synchronization

This is Part 2 of a trio of papers intended to provide a unifying framework in which conservative and optimistic synchronization for parallel discrete event simulations (PDES) can be freely and transparently combined in the same logical process (LP) on an event-by-event basis. In this paper we continue the outline of an approach called Unified Virtual Time (UVT) that was introduced in Part 1 , and show in detail via two extended examples how conservative synchronization can be refactored and combined with optimistic synchronization in the UVT framework. We describe UVT versions of both a basic time windowing algorithm called USTW (Unified Simple Time Windows) and a refactored version of the Chandy-Misra-Bryant Null Message algorithm called UCMB (Unified CMB) .