A Unit Two Variable per Inequality Integer Constraint Solver for Constraint Logic Programming

One of the problems with the traditional nite domains approach to solving integer problems in a constraint logic programming context is that all variables require explicit bounds. If no explicit bounds are available then the nite domain solver can be very ineecient on certain classes of problem. We present an alternative approach to solving integer constraints based on a polynomial-time solver for a restricted class of integer constraints. This approach does not require bounds information, avoids bad behaviour for a larger class of problems, and is competitive with bounds propagation for the types of problem examined. We give a detailed description of the implementation of the core solver, discuss how it can be used to as the basis of a more general solver, and present some computational results.