The SeqBin constraint revisited

Abstract

We revisit the SeqBin constraint [1]. This meta-constraint subsumes a number of important global constraints like Change [2], Smooth [3] and IncreasingNValue [4]. We show that the previously proposed filtering algorithm for SeqBin has two drawbacks even under strong restrictions: it does not detect bounds disentailment and it is not idempotent. We identify the cause for these problems, and propose a new propagator that overcomes both issues. Our algorithm is based on a connection to the problem of finding a path of a given cost in a restricted n-partite graph. Our propagator enforces domain consistency in O(nd 2) and, for special cases of SeqBin that include Change, Smooth and IncreasingNValue in O(nd) time. © 2012 Springer-Verlag.