State space reduction using Predicate Filters

In a previous paper, we presented a technique called finite trace covers, in which a program is represented by a set of partial orders. We also presented classes of reachability properties that could be checked in time that is polynomial in the size of the trace cover. A deficiency of this approach was that it did not reduce the complexity of checking properties that did not belong to an efficient class. In this paper, we present a technique called predicate filtering, which can be used as a state space reduction technique to reduce the complexity of checking general reachability properties. To verify a property φ that does not belong to one of our efficient property classes, the user can first specify a weaker property ψ, which belongs to an efficient class. The program is filtered through the property ψ. The result is a set of partial orders, which can be represented as programs, and contain all the states that satisfy ψ, while eliminating most of the states that do not. Traditional model checking techniques can then be used to verify φ on the reduced program. In experiments, we verified a leader election protocol by constructing only one-third as many states as constructed by SPIN using partial order reduction.