884 research outputs found
Translation-based Constraint Answer Set Solving
We solve constraint satisfaction problems through translation to answer set
programming (ASP). Our reformulations have the property that unit-propagation
in the ASP solver achieves well defined local consistency properties like arc,
bound and range consistency. Experiments demonstrate the computational value of
this approach.Comment: Self-archived version for IJCAI'11 Best Paper Track submissio
SAT Modulo Monotonic Theories
We define the concept of a monotonic theory and show how to build efficient
SMT (SAT Modulo Theory) solvers, including effective theory propagation and
clause learning, for such theories. We present examples showing that monotonic
theories arise from many common problems, e.g., graph properties such as
reachability, shortest paths, connected components, minimum spanning tree, and
max-flow/min-cut, and then demonstrate our framework by building SMT solvers
for each of these theories. We apply these solvers to procedural content
generation problems, demonstrating major speed-ups over state-of-the-art
approaches based on SAT or Answer Set Programming, and easily solving several
instances that were previously impractical to solve
ASAP: An Automatic Algorithm Selection Approach for Planning
Despite the advances made in the last decade in automated planning, no planner out-
performs all the others in every known benchmark domain. This observation motivates
the idea of selecting different planning algorithms for different domains. Moreover, the
plannersâ performances are affected by the structure of the search space, which depends
on the encoding of the considered domain. In many domains, the performance of a plan-
ner can be improved by exploiting additional knowledge, for instance, in the form of
macro-operators or entanglements.
In this paper we propose ASAP, an automatic Algorithm Selection Approach for
Planning that: (i) for a given domain initially learns additional knowledge, in the form
of macro-operators and entanglements, which is used for creating different encodings
of the given planning domain and problems, and (ii) explores the 2 dimensional space
of available algorithms, defined as encodingsâplanners couples, and then (iii) selects the
most promising algorithm for optimising either the runtimes or the quality of the solution
plans
A lower bound on CNF encodings of the at-most-one constraint
Constraint "at most one" is a basic cardinality constraint which requires
that at most one of its boolean inputs is set to . This constraint is
widely used when translating a problem into a conjunctive normal form (CNF) and
we investigate its CNF encodings suitable for this purpose. An encoding differs
from a CNF representation of a function in that it can use auxiliary variables.
We are especially interested in propagation complete encodings which have the
property that unit propagation is strong enough to enforce consistency on input
variables. We show a lower bound on the number of clauses in any propagation
complete encoding of the "at most one" constraint. The lower bound almost
matches the size of the best known encodings. We also study an important case
of 2-CNF encodings where we show a slightly better lower bound. The lower bound
holds also for a related "exactly one" constraint.Comment: 38 pages, version 3 is significantly reorganized in order to improve
readabilit
Analysis of Feature Models Using Alloy: A Survey
Feature Models (FMs) are a mechanism to model variability among a family of
closely related software products, i.e. a software product line (SPL). Analysis
of FMs using formal methods can reveal defects in the specification such as
inconsistencies that cause the product line to have no valid products. A
popular framework used in research for FM analysis is Alloy, a light-weight
formal modeling notation equipped with an efficient model finder. Several works
in the literature have proposed different strategies to encode and analyze FMs
using Alloy. However, there is little discussion on the relative merits of each
proposal, making it difficult to select the most suitable encoding for a
specific analysis need. In this paper, we describe and compare those strategies
according to various criteria such as the expressivity of the FM notation or
the efficiency of the analysis. This survey is the first comparative study of
research targeted towards using Alloy for FM analysis. This review aims to
identify all the best practices on the use of Alloy, as a part of a framework
for the automated extraction and analysis of rich FMs from natural language
requirement specifications.Comment: In Proceedings FMSPLE 2016, arXiv:1603.0857
Recognition and Exploitation of Gate Structure in SAT Solving
In der theoretischen Informatik ist das SAT-Problem der archetypische Vertreter der Klasse der NP-vollstÀndigen Probleme, weshalb effizientes SAT-Solving im Allgemeinen als unmöglich angesehen wird.
Dennoch erzielt man in der Praxis oft erstaunliche Resultate, wo einige Anwendungen Probleme mit Millionen von Variablen erzeugen, die von neueren SAT-Solvern in angemessener Zeit gelöst werden können.
Der Erfolg von SAT-Solving in der Praxis ist auf aktuelle Implementierungen des Conflict Driven Clause-Learning (CDCL) Algorithmus zurĂŒckzufĂŒhren, dessen LeistungsfĂ€higkeit weitgehend von den verwendeten Heuristiken abhĂ€ngt, welche implizit die Struktur der in der industriellen Praxis erzeugten Instanzen ausnutzen.
In dieser Arbeit stellen wir einen neuen generischen Algorithmus zur effizienten Erkennung der Gate-Struktur in CNF-Encodings von SAT Instanzen vor, und auĂerdem drei AnsĂ€tze, in denen wir diese Struktur explizit ausnutzen.
Unsere BeitrĂ€ge umfassen auch die Implementierung dieser AnsĂ€tze in unserem SAT-Solver Candy und die Entwicklung eines Werkzeugs fĂŒr die verteilte Verwaltung von Benchmark-Instanzen und deren Attribute, der Global Benchmark Database (GBD)
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