PKML with ClpZinc: A Compilation Chain from Search Strategies to Solvers, and its Use for Packing

Constraint programming is traditionally viewed as the combination of two components: a constraint model and a search procedure. On the other hand, packing seems to be a widely studied application of constraint programming. In this paper we present two languages: (i) ClpZinc, showing that tree search procedures can be fully internalized in the constraint model, and (ii) PKML a language for expressing symbolic packing relations among objects and their components (e.g., Allen relations between one-dimension shapes, symbolic relations between multidimension shapes, and symbolic relations among straight objects and their possible alternative shapes). The latter is implemented in the former, and reaches solvers through Zinc high-level models. PKML is evaluated on Korf’s problem, improving the best performances [17] on several problem instances; it is also evaluated on an industrial problem with real data and complex spatial relations. Finally, the compilation chain from PKML to solvers is extended to real numbers.