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ValAsp: a tool for data validation in Answer Set programming

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arXiv 2022年

作者： Alviano, Mario Dodaro, Carmine Zamayla, Arnel 87036 Italy

The development of complex software requires tools promoting fail-fast approaches, so that bugs and unexpected behavior can be quickly identified and fixed. Tools for data validation may save the day of computer programmers. In fact, processing invalid data is a waste of resources at best, and a drama at worst if the problem remains unnoticed and wrong results are used for business. Answer Set programming (ASP) is not an exception, but the quest for better and better performance resulted in systems that essentially do not validate data. Even under the simplistic assumption that input/output data are eventually validated by external tools, invalid data may appear in other portions of the program, and go undetected until some other module of the designed software suddenly breaks. This paper formalizes the problem of data validation for ASP programs, introduces a language to specify data validation, and presents VALASP, a tool to inject data validation in ordinary programs. The proposed approach promotes fail-fast techniques at coding time without imposing any lag on the deployed system if data are pretended to be valid. Validation can be specified in terms of statements using YAML, ASP and Python. Additionally, the proposed approach opens the possibility to use ASP for validating data of imperative programming languages. Under consideration for acceptance in TPLP. Copyright © 2022, The Authors. All rights reserved.

关键词： logic programming

Using answer set programming for HPC dependency solving 22

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Using answer set programming for HPC dependency solving

Proceedings of the International Conference on High Performance Computing, Networking, Storage and Analysis

作者： Todd Gamblin Massimiliano Culpo Gregory Becker Sergei Shudler Lawrence Livermore National Laboratory np-complete S.r.l. Italy

Modern scientific software stacks have become extremely complex, using many programming models and libraries to exploit a growing variety of GPUs and accelerators. Package managers can mitigate this complexity using dependency solvers, but they are reaching their limits. Finding compatible dependency versions is NP-complete, and modeling the semantics of package compatibility modulo build-time options, GPU runtimes, flags, and other parameters is extremely difficult. Within this enormous configuration space, defining a "good" configuration is *** tackle this problem using Answer Set programming (ASP), a declarative model for combinatorial search problems. We show, using the Spack package manager, that ASP programs can concisely express the compatibility rules of HPC software stacks and provide strong quality-of-solution guarantees. Using ASP, we can mix new builds with preinstalled binaries, and solver performance is acceptable even when considering tens of thousands of packages.

关键词： logic programming software packages high performance computing dependency management package management software reusability answer set programming

On the Configuration of More and Less Expressive logic Programs

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arXiv 2022年

作者： Dodaro, Carmine Maratea, Marco Vallati, Mauro University of Calabria Italy University of Genoa Italy University of Huddersfield United Kingdom

The decoupling between the representation of a certain problem, i.e., its knowledge model, and the reasoning side is one of main strong points of model-based Artificial Intelligence (AI). This allows, e.g. to focus on improving the reasoning side by having advantages on the whole solving process. Further, it is also well-known that many solvers are very sensitive to even syntactic changes in the input. In this paper, we focus on improving the reasoning side by taking advantages of such sensitivity. We consider two well-known model-based AI methodologies, SAT and ASP, define a number of syntactic features that may characterise their inputs, and use automated configuration tools to reformulate the input formula or program. Results of a wide experimental analysis involving SAT and ASP domains, taken from respective competitions, show the different advantages that can be obtained by using input reformulation and configuration. Under consideration in Theory and Practice of logic programming (TPLP). Copyright © 2022, The Authors. All rights reserved.

关键词： logic programming

Exploiting Game Theory for Analysing Justifications

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THEORY AND PRACTICE OF logic programming 2020年第6期20卷 880-894页

作者： MARYNISSEN, S. I. M. O. N. BOGAERTS, B. A. R. T. DENECKER, M. A. R. C. Katholieke Univ Leuven Leuven Belgium Vrije Univ Brussel Brussels Belgium

Justification theory is a unifying semantic framework. While it has its roots in non-monotonic logics, it can be applied to various areas in computer science, especially in explainable reasoning;its most central concept is a justification: an explanation why a property holds (or does not hold) in a model. In this paper, we continue the study of justification theory by means of three major contributions. The first is studying the relation between justification theory and game theory. We show that justification frameworks can be seen as a special type of games. The established connection provides the theoretical foundations for our next two contributions. The second contribution is studying under which condition two different dialects of justification theory (graphs as explanations vs trees as explanations) coincide. The third contribution is establishing a precise criterion of when a semantics induced by justification theory yields consistent results. In the past proving that such semantics were consistent took cumbersome and elaborate proofs. We show that these criteria are indeed satisfied for all common semantics of logic programming.

关键词： justification theory positional games logic programming non-monotonic logic

Reduction-based Solving of Multi-agent Pathfinding on Large Maps Using Graph Pruning 22

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Reduction-based Solving of Multi-agent Pathfinding on Large ...

Proceedings of the 21st International Conference on Autonomous Agents and Multiagent Systems

作者： Matej Husár Jirí Švancara Philipp Obermeier Roman Barták Torsten Schaub Charles University Prague Czech Rep University of Potsdam Potsdam Germany Potassco Solutions & University of Potsdam Potsdam Germany

ISBN: (纸本)9781450392136

Multi-agent pathfinding is the problem of finding collision-free paths for a set of agents. Solving this problem optimally is computationally hard, therefore many techniques based on reductions to other formalisms were developed. In comparison to search-based techniques, the reduction-based techniques fall behind on large maps even for a small number of agents. To combat this phenomenon, we propose several strategies for pruning vertices off large instances that will most likely not be used by agents. First, we introduce these strategies conceptually and prove which of them maintain completeness and optimality. Eventually, we conduct an exhaustive evaluation and show that graph pruning strategies make reduction-based solvers comparable to search-based techniques on large maps while maintaining their advantage on small dense maps.

关键词： satisfiability logic programming answer set programming scalability multi-agent pathfinding graph pruning subgraph

A Neuro-Symbolic ASP Pipeline for Visual Question Answering

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arXiv 2022年

作者： Eiter, Thomas Higuera, Nelson Oetsch, Johannes Pritz, Michael Austria

We present a neuro-symbolic visual question answering (VQA) pipeline for CLEVR, which is a well-known dataset that consists of pictures showing scenes with objects and questions related to them. Our pipeline covers (i) training neural networks for object classification and bounding-box prediction of the CLEVR scenes, (ii) statistical analysis on the distribution of prediction values of the neural networks to determine a threshold for high-confidence predictions, and (iii) a translation of CLEVR questions and network predictions that pass confidence thresholds into logic programs so that we can compute the answers using an ASP solver. By exploiting choice rules, we consider deterministic and non-deterministic scene encodings. Our experiments show that the non-deterministic scene encoding achieves good results even if the neural networks are trained rather poorly in comparison with the deterministic approach. This is important for building robust VQA systems if network predictions are less-than perfect. Furthermore, we show that restricting non-determinism to reasonable choices allows for more efficient implementations in comparison with related neuro-symbolic approaches without loosing much accuracy. This work is under consideration for acceptance in TPLP. © 2022, CC BY.

关键词： logic programming

CHC-COMP 2022: Competition Report

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arXiv 2022年

作者： De Angelis, Emanuele Hari Govind, V.K. IASI-CNR Italy University of Waterloo Canada

CHC-COMP 2022 is the fifth edition of the competition of solvers for Constrained Horn Clauses. The competition was run in March 2022;the results were presented at the 9th Workshop on Horn Clauses for Verification and Synthesis held in Munich, Germany, on April 3, 2022. This edition featured six solvers, and eight tracks consisting of sets of linear and nonlinear clauses with constraints over linear integer arithmetic, linear real arithmetic, arrays, and algebraic data types. This report provides an overview of the organization behind the competition runs: it includes the technical details of the competition setup as well as presenting the results of the 2022 edition. © 2022, CC BY.

关键词： logic programming

The generalised distribution semantics and projective families of distributions

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arXiv 2022年

作者： Weitkämper, Felix Institut für Informatik Ludwig-Maximilians-Universität München Oettingenstr. 67 München80538 Germany

We generalise the distribution semantics underpinning probabilistic logic programming by distilling its essential concept, the separation of a free random component and a deterministic part. This abstracts the core ideas beyond logic programming as such to encompass frameworks from probabilistic databases, probabilistic finite model theory and discrete lifted Bayesian networks. To demonstrate the usefulness of such a general approach, we completely characterise the projective families of distributions representable in the generalised distribution semantics and we demonstrate both that large classes of interesting projective families cannot be represented in a generalised distribution semantics and that already a very limited fragment of logic programming (acyclic determinate logic programs) in the deterministic part suffices to represent all those projective families that are representable in the generalised distribution semantics at all. © 2022, CC BY.

关键词： logic programming

CROSSBEAM: LEARNING TO SEARCH IN BOTTOM-UP PROGRAM SYNTHESIS

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arXiv 2022年

作者： Shi, Kensen Dai, Hanjun Ellis, Kevin Sutton, Charles Google Research Cornell University United States

Many approaches to program synthesis perform a search within an enormous space of programs to find one that satisfies a given specification. Prior works have used neural models to guide combinatorial search algorithms, but such approaches still explore a huge portion of the search space and quickly become intractable as the size of the desired program increases. To tame the search space blowup, we propose training a neural model to learn a hands-on search policy for bottom-up synthesis, instead of relying on a combinatorial search algorithm. Our approach, called CROSSBEAM, uses the neural model to choose how to combine previously-explored programs into new programs, taking into account the search history and partial program executions. Motivated by work in structured prediction on learning to search, CROSSBEAM is trained on-policy using data extracted from its own bottom-up searches on training tasks. We evaluate CROSSBEAM in two very different domains, string manipulation and logic programming. We observe that CROSSBEAM learns to search efficiently, exploring much smaller portions of the program space compared to the state-of-the-art. Copyright © 2022, The Authors. All rights reserved.

关键词： logic programming