Clingcon: The Next Generation
  We present the third generation of the constraint answer set system clingcon,
combining Answer Set Programming (ASP) with finite domain constraint processing
(CP). While its predecessors rely on a black-box approach to hybrid solving by
integrating the CP solver gecode, the new clingcon system pursues a lazy
approach using dedicated constraint propagators to extend propagation in the
underlying ASP solver clasp. No extension is needed for parsing and grounding
clingcon's hybrid modeling language since both can be accommodated by the new
generic theory handling capabilities of the ASP grounder gringo. As a whole,
clingcon 3 is thus an extension of the ASP system clingo 5, which itself relies
on the grounder gringo and the solver clasp. The new approach of clingcon
offers a seamless integration of CP propagation into ASP solving that benefits
from the whole spectrum of clasp's reasoning modes, including for instance
multi-shot solving and advanced optimization techniques. This is accomplished
by a lazy approach that unfolds the representation of constraints and adds it
to that of the logic program only when needed. Although the unfolding is
usually dictated by the constraint propagators during solving, it can already
be partially (or even totally) done during preprocessing. Moreover, clingcon's
constraint preprocessing and propagation incorporate several well established
CP techniques that greatly improve its performance. We demonstrate this via an
extensive empirical evaluation contrasting, first, the various techniques in
the context of CSP solving and, second, the new clingcon system with other
hybrid ASP systems. Under consideration in Theory and Practice of Logic
Programming (TPLP)
