A Hybrid Algorithm for Compiling Equality Constraints and its Implementation

In this paper, we extend the language we proposed in [11] to make it possible to program arc-consistency algorithms. We also propose a hybrid algorithm that integrates the interval-consistency (IC) and arc-consistency (AC) algorithms. For a constraint, the algorithm checks IC when it is non-binary and checks AC when the constraint turns into binary. The algorithm is well-balanced. Its reduction cost is close to the IC checking algorithm, while its reduction power is close to the AC checking algorithm for most problems. The experimental results show that the hybrid algorithm may be a little slower than the IC checking algorithm for programs that do not require strong reduction power, but may be an order of magnitude faster than IC for other programs.