Speeding up Lazy-Grounding Answer Set Solving

The grounding bottleneck is an important open issue in Answer Set Programming. Lazy grounding addresses it by interleaving grounding and search. The performance of current lazy-grounding solvers is not yet comparable to that of ground-and-solve systems, however. The aim of this thesis is to extend prior work on lazy grounding by novel heuristics and other techniques like non-ground conflict learning in order to speed up solving. Parts of expected results will be beneficial for ground-and-solve systems as well

Specifying and Exploiting Non-Monotonic Domain-Specific Declarative Heuristics in Answer Set Programming

Domain-specific heuristics are an essential technique for solving combinatorial problems efficiently. Current approaches to integrate domain-specific heuristics with Answer Set Programming (ASP) are unsatisfactory when dealing with heuristics that are specified non-monotonically on the basis of partial assignments. Such heuristics frequently occur in practice, for example, when picking an item that has not yet been placed in bin packing. Therefore, we present novel syntax and semantics for declarative specifications of domain-specific heuristics in ASP. Our approach supports heuristic statements that depend on the partial assignment maintained during solving, which has not been possible before. We provide an implementation in ALPHA that makes ALPHA the first lazy-grounding ASP system to support declaratively specified domain-specific heuristics. Two practical example domains are used to demonstrate the benefits of our proposal. Additionally, we use our approach to implement informed} search with A*, which is tackled within ASP for the first time. A* is applied to two further search problems. The experiments confirm that combining lazy-grounding ASP solving and our novel heuristics can be vital for solving industrial-size problems

Einfluss von Sprachkonstrukten auf die Lösbarkeit von Answer-Set-Programmen : eine empirische Untersuchung aktueller ASP-Systeme

Richard TaupeZsfassung in engl. SpracheKlagenfurt, Alpen-Adria-Univ., Master-Arb., 2015(VLID)241515

Exploiting partial knowledge in declarative domain-specific heuristics for ASP

| openaire: EC/H2020/825619/EU//AI4EUDomain-specific heuristics are an important technique for solving combinatorial problems efficiently. We propose a novel semantics for declarative specifications of domain-specific heuristics in Answer Set Programming (ASP). Decision procedures that are based on a partial solution are a frequent ingredient of existing domain-specific heuristics, e.g., for placing an item that has not been placed yet in bin packing. Therefore, in our novel semantics negation as failure and aggregates in heuristic conditions are evaluated on a partial solver state. State-of-the-art solvers do not allow such a declarative specification. Our implementation in the lazy-grounding ASP system Alpha supports heuristic directives under this semantics. By that, we also provide the first implementation for incorporating declaratively specified domain-specific heuristics in a lazy-grounding setting. Experiments confirm that the combination of ASP solving with lazy grounding and our novel heuristics can be a vital ingredient for solving industrial-size problems.Peer reviewe

Solver Requirements for Interactive Configuration

Interactive configuration includes the user as an essential factor in the configuration process. The two main components of an interactive configurator are a user interface at the front-end and a knowledge representation and reasoning (KRR) framework at the back-end. In this paper we discuss important requirements for the underlying KRR system to support an interactive configuration process. Representative of many reasoning systems and tools used for implementing product configurators, we selected MiniZinc, Choco, Potassco, Picat, CP-SAT solver, and Z3 for evaluation and reviewed them against the identified requirements. We observe that many of those requirements are not well supported by existing stand-alone solvers