Model Checking Randomized Algorithms with Java PathFinder

On the one hand, probabilistic model checkers such as PRISM have been successfully employed to verify models of probabilistic systems. However, they are not suitable for checking properties such as uncaught exceptions of the actual code of the system. On the other hand, model checkers such as Java PathFinder (JPF) have been used with success to verify actual code of systems. However, they do not take into account the probabilities associated with the probabilistic choices of the systems. In this paper, we bridge the gap by extending JPF so that it takes those probabilities into account. We introduce a method to express a probabilistic choice in Java so that JPF can easily extract the probabilities of the alternatives of the probabilistic choice. By default, JPF traverses the state space using a depth-first search or a breadth-first search. We have implemented in JPF several search strategies which use the probabilities associated with the alternatives of probabilistic choices. To address the state explosion problem, we keep track of the amount of progress made by JPF.