A Sound Dynamic Partial Order Reduction Engine for Java Pathfinder

Abstract

When model checking a multi-threaded program, it is often nec- essary to enumerate the possible ordering of concurrent events to evaluate the behavior of the program. However, enumerating every possible order of events quickly leads to state-space explo- sion. Dynamic Partial Order Reduction (DPOR) is a method to dynamically determine a subset of schedules that need to be evaluated to observe all the relevant behavior of a program. A sound implementation of DPOR in Java Path nder (JPF) can be tricky without incurring unacceptable amounts of overhead, be- cause JPF does not support subdividing existing transitions and conservatively inserting choice generators to end transitions at each possible scheduling point causes JPF to save a large amount of state. We present an extension to JPF, which is an efficient implementation of DPOR that attempts to minimize spacial com- plexity. It handles the directing of the search and uses a simple interface to allow the user to de ne the set of events to operate on and to determine which of those events are dependent. It keeps its own internal representation of all possible scheduling points without inserting choice generators at each point. It then restarts portions of the search, if necessary, to insert only the needed choice generators.