Experience in retrofitting a large sequential Ada simulator to two versions of time warp

The Extended Air Defense Testbed (EADTB), is a comprehensive, high- and mixed-level-of-detail, environment for modeling weapon system entities and interactions. Due to the complexity of the models and large scenario sizes, in its current single-threaded form, EADTB is limited in run-time speed. Our goal is to speed up the simulation without re-architecture or re-implementation of the models which comprise 1.76 million lines of Ada code, and without altering model behavior or compromising repeatability and causality. Our work demonstrates that the use of optimistic scheduling techniques and its derivatives, offers the best alternative for object-based systems like EADTB. Specifically we have retrofitted and integrated the same representative pseudo-EADTB prototype with two different object-oriented optimistic scheduling engines (SPEEDES and TEMPO/Thema). We discuss the required architectural and behavioral features of a simulation to allow this retrofit, the issues of C++ to Ada language interfaces, and the employment of the basic services of the optimistic scheduling engines in this environment. Experimental results suggest that order-of-magnitude speed-up is feasible through parallelization, and is scalable to larger experiments simply by adding hardware