279 research outputs found
Finite domain constraints in SICStus prolog
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Specialising finite domain programs with polyhedra
A procedure is described for tightening domain constraints of finite domain logic programs by applying a static analysis based on convex polyhedra. Individual finite domain constraints are over-approximated by polyhedra to describe the solution space over ninteger variables as an n dimensional polyhedron. This polyhedron is then approximated, using projection, as an n dimensional bounding box that can be used to specialise and improve the domain constraints. The analysis can be implemented straightforwardly and an empirical evaluation of the specialisation technique is given
Solving Functional Constraints by Variable Substitution
Functional constraints and bi-functional constraints are an important
constraint class in Constraint Programming (CP) systems, in particular for
Constraint Logic Programming (CLP) systems. CP systems with finite domain
constraints usually employ CSP-based solvers which use local consistency, for
example, arc consistency. We introduce a new approach which is based instead on
variable substitution. We obtain efficient algorithms for reducing systems
involving functional and bi-functional constraints together with other
non-functional constraints. It also solves globally any CSP where there exists
a variable such that any other variable is reachable from it through a sequence
of functional constraints. Our experiments on random problems show that
variable elimination can significantly improve the efficiency of solving
problems with functional constraints
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