Ordinal optimization approach to rare event probability problems

In this paper we introduce a new approach to rare event simulation. Because of the extensive simulation required for precise estimation of performance criterion dependent on rare event occurrences, obstacles such as computing budget/time constraints and pseudo-random number generator limitations can become prohibitive, particularly if comparative study of different system designs is involved. Existing methods for rare events simulation have focused on simulation budget reduction while attempting to generate accurate performance estimates. In this paper we propose a new approach for rare events system analysis in which we relax the simulation goal to the isolation of a set of “good enough” designs with high probability. Given this relaxation, referred to as Ordinal Optimization and advanced by Ho-Sreenivas-Vakili (1992), this paper’s approach calls instead for the consideration of an appropriate surrogate design problem. This surrogate problem is characterized by its approximate ordinal equivalence to the original problem and its performance criterion’s dependence not on rare event occurrences, but on more frequent events. Evaluation of such a surrogate problem under the relaxed goals of Ordinal Optimization has experimentally resulted in orders of magnitude reduction in simulation burden.