Exploiting temporal uncertainty in parallel and distributed simulations

Parallel discrete event simulation algorithms are usually based on time stamp ordering of events. Distributed virtual environment (DVE) applications such as DIS typically use unordered event delivery. A partial order called approximate time (AT) is proposed to order events in both domains, facilitating reuse of simulations across DVE and analysis applications. A variation on AT-order called approximate time causal (ATC) order is also described. Synchronisation algorithms to realize these orderings are presented as well as performance measurements on a workstation cluster. A long-term goal of this work is to use AT and ATC order to exploit temporal uncertainty in the model to achieve efficient conservative parallel simulation despite little or no lookahead, a long-standing problem in the field.