Automating Verification of Loops by Parallelization

摘要

Loops are a major bottleneck in formal software verification, because they generally require user interaction: typically, induction hypotheses or invariants must be found or modified by hand. This involves expert knowledge of the underlying calculus and proof engine. We show that one can replace interactive proof techniques, such as induction, with automated first-order reasoning in order to deal with parallelizable loops, where a loop can be parallelized whenever it avoids dependence of the loop iterations from each other. We develop a dependence analysis that ensures parallelizability. It guarantees soundness of a proof rule that transforms a loop into a universally quantified update of the state change information represented by the loop body. This makes it possible to use automatic first order reasoning techniques to deal with loops. The method has been implemented in the KeY verification tool. We evaluated it with representative case studies from the Java Card domain.