An Experiment in Simulation Coercion

If simulations could be coerced -- literally reshaped -- to conform to requirements different from those for which they were originally designed, many of the challenges facing the simulation community should become less daunting. Success could foster reuse, enable linkages between multi-resolution models, and increase the chances of success for interoperability and composability. We consider coercing as it applies to multi-resolution modeling. Given two simulations of the same phenomenon at different levels of detail, we explore coercing the lower resolution simplified simulation to produce results that correspond satisfactorily with the detailed high resolution simulation. The product is a simulation possessing the speed of the low resolution simulation along with the desired accuracy of the high resolution simulation. Coercing involves a subject matter expert and optimization. The subject matter expert selects simulation parameters and establishes constraints within which those parameters are allowed to vary without compromising the validity of the simulation. Then, an optimization technique is employed to search through the possible parameter values and to select that set for which the simulation results most closely reflect the ideal; namely, conformance with new requirements stemming from the high resolution model. To explore the concept of coercing simulations, we selected a high resolution three-dimensional bicyclist simulation and a simple simulation of a particle moving in two-dimensional space as the low resolution simulation. For these two simulations, we were able to modify, using optimization, the parameters of the low resolution simulation to follow a route that more accurately reflected the route traced by the three-dimensional bicyclist on a given course. We report on our coercing experience, providing detailed insight into the process we have designed for coercing, and we describe results. Also, we discuss automating additional phases of the coercion process and their integration into our evolving coercion tool, SimEx.