Partial-Order Reduction for General State Exploring Algorithms

Abstract

AbstractAn important component of partial-order based reduction algorithms is the condition that prevents action ignoring, commonly known as the cycle proviso. In this paper we give a new version of this proviso that is applicable to a general search algorithm skeleton also known as the General State Expanding Algorithm (GSEA). GSEA maintains a set of open (visited but not expanded) states from which states are iteratively selected for exploration and moved to a closed set of states (visited and expanded). Depending on the open set data structure used, GSEA can be instantiated as depth-first, breadth-first, or a directed search algorithm. The proviso is characterized by reference to the open and closed set of states in GSEA. As a result the proviso can be computed in an efficient manner during the search based on local information. We implemented partial-order reduction for GSEA based on our proposed proviso in the tool HSF-SPIN, which is an extension of the model checker SPIN for directed model checking. We evaluate the state space reduction achieved by partial-order reduction according to the proviso that we propose by comparing it on a set of benchmark problems to other reduction approaches. We also compare the use of breadth-first search and A*, two algorithms ensuring that counterexamples of minimal length will be found, together with the proviso that we propose.KeywordsState SpaceModel CheckSafety PropertyLabel Transition SystemExecution SequenceThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.