Although logic languages, due to their non-declarative nature, are widely proclaimed to be conducive in theory to parallel implementation, in fact there appears to be insufficient practical evidence to stimulate furth...
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Although logic languages, due to their non-declarative nature, are widely proclaimed to be conducive in theory to parallel implementation, in fact there appears to be insufficient practical evidence to stimulate further developments in this field, The paper puts forward various complications which arise in assuming a solely process parallel approach as a possible explanation for this situation. As an alternative, data parallelism is posited as an underutilized forte of logicprogramming, The paper illustrates a data parallel implementation of a particular language called SEL which is based on sets, Thus, SEL (set equational language) is introduced as an example of logic language which lends itself to an efficient data parallel implementation. The strategy of this implementation assumes an abstract machine called SAM (set-oriented abstract machine) which is based on the WAM (Warren abstract machine), SAM serves as an intermediary between the SEL language and the target machine for the implementation, the Connection Machine, Finally some preliminary benchmarks are presented.
The efficiency of resolution-based logicprogramming languages, such as Prolog, depends critically on selecting and executing sets of applicable clause heeds to resolve against subgoals. Traditional approaches to this...
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The efficiency of resolution-based logicprogramming languages, such as Prolog, depends critically on selecting and executing sets of applicable clause heeds to resolve against subgoals. Traditional approaches to this problem have focused on using indexing to determine the smallest possible applicable set. Despite their usefulness, these approaches ignore the nondeterminism inherent in many programming languages to the extent that they do not attempt to optimize execution after the applicable set has been determined. Unification factoring seeks to rectify this omission by regarding the indexing and unification phases of clause resolution as a single process. This article formalizes that process through the construction of factoring automata. A polynomial-time algorithm is given for constructing optimal factoring automate that preserve the clause selection strategy of Prolog. More generally when the clause selection strategy is not fixed, constructing such an optimal automaton is shown to be NP-complete, solving an open trie minimization problem. Unification factoring is implemented through a source code transformation that preserves the full semantics of Prolog. This transformation is specified in the cuticle, and using it, several well-known programs show significant performance improvements across several different systems. A prototype of unification factoring is available by anonymous ftp.
A logic view of 0-1 integer programming problems, providing new insights into the structure of problems that can lead the researcher to more effective solution techniques depending on the problem class. Operations ...
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ISBN:
(数字)9781461313151
ISBN:
(纸本)9781461313151
A logic view of 0-1 integer programming problems, providing new insights into the structure of problems that can lead the researcher to more effective solution techniques depending on the problem class. Operations research techniques are integrated into a logicprogramming environment. The first monographic treatment that begins to unify these two methodological approaches.;logic-based methods for modelling and solving combinatorial problems have recently started to play a significant role in both theory and practice. The application of logic to combinatorial problems has a dual aspect. On one hand,;allows one to declaratively model combinatorial problems over an appropriate constraint domain, the problems then being solved by a corresponding constraint solver. Besides being a high-level declarative interface to the constraint solver, the logicprogramming language allows one also to implement those subproblems that cannot be naturally expressed with constraints. On the other hand, logic-based methods can be used as a;technique within a constraint solver for combinatorial problems modelled as 0-1 integer programs.
Type inference is the compile-time process of reconstructing missing type information in a program based on the usage of its variables. ML and Haskell are two languages where this aspect of compilation has enjoyed som...
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Type inference is the compile-time process of reconstructing missing type information in a program based on the usage of its variables. ML and Haskell are two languages where this aspect of compilation has enjoyed some popularity, allowing type information to be omitted while static type checking is still performed. Type inference may be expected to have some application in the prototyping and scripting languages which are becoming increasingly popular. A difficulty with type inference is the confusing and sometimes counter-intuitive diagnostics produced by the type checker as a result of type errors. A modification of the unification algorithm used in Hindley-Milner type inference is presented, which allows the specific reasoning which led to a program variable having a particular type to be recorded for type explanation. This approach is close to the intuitive process used in practice for debugging type errors. The algorithm is practical, and has been implemented in the Standard ML of New Jersey compiler. The modified unification algorithm also appears useful in other domains, including logic program debuggers and semantics-based programming environments.
In preparation for the changeover to a new modular degree structure, at the University of Leeds, a new modular timetable for the 1993-94 academic session had to be constructed from scratch. This paper describes our ex...
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The proceedings contain 24 papers. The special focus in this conference is on practice and theory of Automated Timetabling. The topics include: Recent developments in practical examination timetabling;computer-aided s...
ISBN:
(纸本)3540617949
The proceedings contain 24 papers. The special focus in this conference is on practice and theory of Automated Timetabling. The topics include: Recent developments in practical examination timetabling;computer-aided school and university timetabling;scheduling, timetabling and rostering;examination timetabling in british universities;employee timetabling, constraint networks and knowledge-based rules;automated time table generation using multiple context reasoning with truth maintenance;investigations of a constraint logicprogramming approach to university timetabling;building university timetables using constraint logicprogramming;complete university modular timetabling using constraint logicprogramming;using oz for college timetabling;a smart genetic algorithm for university timetabling;a genetic algorithm solving a weekly course-timetabling problem;GA-based examination scheduling experience at middle east technical university;peckish initialisation strategies for evolutionary timetabling;a memetic algorithm for university exam timetabling;extensions to a memetic timetabling system;automatic timetabling in practice;the complexity of timetable construction problems;some combinatorial models for course scheduling;the phase-transition niche for evolutionary algorithms in timetabling;three methods used to solve an examination timetable problem and general cooling schedules for a simulated annealing based timetabling system.
We propose a variant of the Hierarchical Constraint logicprogramming (HCLP) scheme of Borning, Wilson, and others. We consider compositionality and incrementality in Constraint logicprogramming, introduce HCLP, and ...
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The casting of university timetables is a problem which combines classical numerical scheduling techniques with important human considerations. It will be argued here that since the application involves the preference...
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In this paper, we concentrate on a typical scheduling problem: the computation of a timetable for a German college. Like many other scheduling problems, this problem contains a variety of complex constraints and neces...
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