183 research outputs found
Efficient Groundness Analysis in Prolog
Boolean functions can be used to express the groundness of, and trace
grounding dependencies between, program variables in (constraint) logic
programs. In this paper, a variety of issues pertaining to the efficient Prolog
implementation of groundness analysis are investigated, focusing on the domain
of definite Boolean functions, Def. The systematic design of the representation
of an abstract domain is discussed in relation to its impact on the algorithmic
complexity of the domain operations; the most frequently called operations
should be the most lightweight. This methodology is applied to Def, resulting
in a new representation, together with new algorithms for its domain operations
utilising previously unexploited properties of Def -- for instance,
quadratic-time entailment checking. The iteration strategy driving the analysis
is also discussed and a simple, but very effective, optimisation of induced
magic is described. The analysis can be implemented straightforwardly in Prolog
and the use of a non-ground representation results in an efficient, scalable
tool which does not require widening to be invoked, even on the largest
benchmarks. An extensive experimental evaluation is givenComment: 31 pages To appear in Theory and Practice of Logic Programmin
Experimenting with independent and-parallel prolog using standard prolog
This paper presents an approximation to the study of parallel systems using sequential tools. The Independent And-parallelism in Prolog is an example of parallel processing paradigm in the framework of logic programming, and implementations like <fc-Prolog uncover the potential performance of parallel processing. But this potential can also be explored using only sequential systems. Being the spirit of this paper to show how this can be done with a standard system, only standard Prolog will be used in the implementations included. Such implementations include tests for parallelism in And-Prolog, a correctnesschecking
meta-interpreter of <fc-Prolog and a simulator of parallel execution for <fc-Prolog
Transforming floundering into success
We show how logic programs with "delays" can be transformed to programs
without delays in a way which preserves information concerning floundering
(also known as deadlock). This allows a declarative (model-theoretic),
bottom-up or goal independent approach to be used for analysis and debugging of
properties related to floundering. We rely on some previously introduced
restrictions on delay primitives and a key observation which allows properties
such as groundness to be analysed by approximating the (ground) success set.
This paper is to appear in Theory and Practice of Logic Programming (TPLP).
Keywords: Floundering, delays, coroutining, program analysis, abstract
interpretation, program transformation, declarative debuggingComment: Number of pages: 24 Number of figures: 9 Number of tables: non
A correct, precise and efficient integration of set-sharing, freeness and linearity for the analysis of finite and rational tree languages
It is well known that freeness and linearity information positively interact with aliasing information, allowing both the precision and the efficiency of the sharing analysis of logic programs to be improved. In this paper, we present a novel combination of set-sharing with freeness and linearity information, which is characterized by an improved abstract unification operator. We provide a new abstraction function and prove the correctness of the analysis for both the finite tree and the rational tree cases.
Moreover, we show that the same notion of redundant information as identified in Bagnara et al. (2000) and Zaffanella et al. (2002) also applies to this abstract domain combination: this allows for the implementation of an abstract unification operator running in polynomial time and achieving the same precision on all the considered observable properties
A Polyvariant Binding-Time Analysis for Off-line Partial Deduction
We study the notion of binding-time analysis for logic programs. We formalise
the unfolding aspect of an on-line partial deduction system as a Prolog
program. Using abstract interpretation, we collect information about the
run-time behaviour of the program. We use this information to make the control
decisions about the unfolding at analysis time and to turn the on-line system
into an off-line system. We report on some initial experiments.Comment: 19 pages (including appendix) Paper (without appendix) appeared in
Programming Languages and Systems, Proceedings of the European Symposium on
Programming (ESOP'98), Part of ETAPS'98 (Chris Hankin, eds.), LNCS, vol.
1381, 1998, pp. 27-4
Enhanced sharing analysis techniques: a comprehensive evaluation
Sharing, an abstract domain developed by D. Jacobs and A. Langen for the analysis of logic
programs, derives useful aliasing information. It is well-known that a commonly used core
of techniques, such as the integration of Sharing with freeness and linearity information, can
significantly improve the precision of the analysis. However, a number of other proposals for
refined domain combinations have been circulating for years. One feature that is common
to these proposals is that they do not seem to have undergone a thorough experimental
evaluation even with respect to the expected precision gains.
In this paper we experimentally
evaluate: helping Sharing with the definitely ground variables found using Pos, the domain
of positive Boolean formulas; the incorporation of explicit structural information; a full
implementation of the reduced product of Sharing and Pos; the issue of reordering the
bindings in the computation of the abstract mgu; an original proposal for the addition of
a new mode recording the set of variables that are deemed to be ground or free; a refined
way of using linearity to improve the analysis; the recovery of hidden information in the
combination of Sharing with freeness information. Finally, we discuss the issue of whether
tracking compoundness allows the computation of more sharing information
A generic persistence model for CLP systems (and two useful implementations)
This paper describes a model of persistence in (C)LP languages and two different and practically very useful ways to implement this model in current systems. The fundamental idea is that persistence is a characteristic of certain dynamic predicates (Le., those which encapsulate
state). The main effect of declaring a predicate persistent is that the dynamic changes made to such predicates persist from one execution to the next one. After proposing a syntax for declaring persistent predicates, a simple, file-based implementation of the concept is presented and
some examples shown. An additional implementation is presented which stores persistent predicates in an external datábase. The abstraction of the concept of persistence from its implementation allows developing applications
which can store their persistent predicates alternatively in files or databases with only a few simple changes to a declaration stating the location and modality used for persistent storage. The paper presents the model, the implementation approach in both the cases of using files
and relational databases, a number of optimizations of the process (using information obtained from static global analysis and goal clustering), and performance results from an implementation of these ideas
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