Protocols for optimistic synchronization of mixed-mode simulation

The desire to combine the simulation of continuous and discrete simulation models has given rise to the field of mixed-mode simulation. In spite of the considerable research in this area, efficient methods for the synchronization of the two time domains remain elusive. The complexities of parallel mixed-mode simulation have made synchronization an even more important and complex issue. Traditional approaches to this synchronization issue are based on event-driven differential equation simulators. Unfortunately, these approaches are not designed to run efficiently on a network of workstations (NOW). However, this computer/network architecture provides the best cost-performance ratio and is widely available. Towards this end, this dissertation proposes two new synchronization protocols for efficient NOW-based mixed-mode simulation. The synchronization protocols are designed to extend the functionality of an optimistic discrete-event simulator. The protocols allow the discrete-event simulation kernel to handle discrete-event processes as well as processes with their own notion of time. Formal methods are used to illustrate the protocols's generality and applicability. The complete specification and verification of the protocols serves as a detailed requirement analysis of the simulation processes as well as a proof of correctness. The viability of the simulation protocols is demonstrated by their implementation in a mixed-mode simulator. The mixed-mode simulator takes advantage of the generic synchronization protocols to merge differential equation solvers (for the analog models) with an optimistic discrete-event simulator (for the discrete models). From the analysis of mixed-mode simulation performance characteristics, new performance factors that correlate existing discrete-event and differential equation performance factors, were identified. In conclusion, this dissertation presents generic process-based synchronization protocols for parallel mixed-mode simulation on a network of workstations. The correctness of these protocols were formally verified to establish their generality. Towards this end, the minimum requirements for the discrete and continuous simulation paradigms are formally identified. The performance of these protocols is characterized by integrating the protocols into a mixed-mode simulator for VHDL-AMS. This allows the mixed-mode simulator to easily take advantage of several continuous simulation kernels that support frequency and transient analysis.