Chris Myers

Hao Zheng, Andrew Price, Chris Myers

The enormous number of states reachable during explicit model checking is the main bottleneck for scalability. This paper presents approaches of using decision diagrams to represent very large state space compactly and efficiently. This is possible for asynchronous systems as two system states connected by a transition often share many same local portions. Using decision diagrams can significantly reduce memory demand by not using memory to store the redundant information among different states. This paper considers multi-value decision diagrams for this purpose. Additionally, a technique to reduce the runtime overhead of using these diagrams is also described. Experimental results and comparison with the state compression method as implemented in the model checker SPIN show that the approaches presented in this paper are memory efficient for storing large state space with acceptable runtime overhead.

Hao Zheng, Yingying Zhang, Chris Myers

This paper presents an approach to more efficient partial order reduction for model checking concurrent systems. This approach utilizes a compositional reachability analysis to generate over-approximate local state transition models for all processes in a concurrent system where an independence relation and other useful information can be extracted. The extracted independence relation, compared to what can be obtained by statically analyzing the system descriptions, is more precise and refined, therefore leads to more efficient partial order reduction. This approach is demonstrated on a set of concurrent system examples. Significantly higher reduction in state space has been observed in several cases compared to what can be obtained using SPIN.