Optimistic synchronization in HLA based distributed simulation

With the wide use of commercial off-the-shelf (COTS) simulation packages and the advent of the high level architecture (HLA) standard which supports interoperability and reusability, it is desirable to build distributed simulations by linking various types of simulation models developed using best-fit COTS packages. While almost all current work on integrating COTS packages and the HLA is based on conservative synchronization, it is worthwhile to investigate the optimistic synchronization approach. The optimistic approach can exploit parallelism and achieve promising performance in situations where causality errors may occur but in fact seldom occur. In our paper, we introduce a rollback controller using a middleware approach to handle the complex rollback procedure on behalf of the simulation model. To fully utilize the benefits of optimistic synchronization, we also introduce a novel time advance algorithm using the services provided by the HLA. A comparison of performance between the conservative and optimistic synchronization approaches based on a typical reference model is also provided.