Implementing Constraint Retraction for Finite Domains

Constraint retraction, while being certainly a very convenient feature in many situations, is usually not provided in current constraint programming environments. In this paper we describe how constraint retraction can be incorporated in the FD constraint solver and we evaluate its behavior within the clp(FD) system. Experimental results on usual benchmarks and also on classes of problems of increasing connectivity show that in almost all cases the use of our retraction algorithm provides great speed-up with respect to standard methods while not slowing down the clp(FD) system when no retraction is performed.