Incremental formal verification of hardware

Formal verification is a reliable and fully automatic technique for proving correctness of hardware designs. Its main drawback is the high complexity of verification, and this problem is especially acute in regression verification, where a new version of the design, differing from the previous version very slightly, is verified with respect to the same or a very similar property. In this paper, we present an efficient algorithm for incremental verification, based on the ic3 algorithm, that uses stored information from the previous verification runs in order to improve the complexity of re-verifying similar designs on similar properties. Our algorithm applies both to the positive and to the negative results of verification (that is, both when there is a proof of correctness and when there is a counterexample). The algorithm is implemented and experimental results show improvement of up to two orders of magnitude in running time, compared to full verification.