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, 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. The authors introduce a rollback controller using a middleware approach to handle the complex rollback procedure on behalf of the simulation model. A new time advance algorithm is proposed that can fully use the benefits of optimistic synchronization. The article also describes a scalability study showing the experimental results for the two synchronization approaches as the number of simulation components increases.