11 research outputs found
An Improved Continuation Call-Based Implementation of Tabling
Tabled evaluation has been proved an effective method to improve several aspects of goal-oriented query evaluation, including termination and complexity. Several “native” implementations of tabled evaluation have been developed which offer good performance, but many of them require significant changes to the underlying Prolog implementation, including the compiler and the abstract machine. Approaches based on program transformation, which tend to minimize changes to both the Prolog compiler and the abstract machine, have also been proposed, but they often result in lower efficiency. We explore some techniques aimed at combining the best of these worlds, i.e., developing an extensible implementation which requires minimal modifications to the compiler and the abstract machine, and with reasonably good performance. Our preliminary experiments indicate promising results
Tabling as a Library with Delimited Control
Tabling is probably the most widely studied extension of Prolog. But despite
its importance and practicality, tabling is not implemented by most Prolog
systems. Existing approaches require substantial changes to the Prolog engine,
which is an investment out of reach of most systems. To enable more widespread
adoption, we present a new implementation of tabling in under 600 lines of
Prolog code. Our lightweight approach relies on delimited control and provides
reasonable performance.Comment: 15 pages. To appear in Theory and Practice of Logic Programming
(TPLP), Proceedings of ICLP 201
A Sketch of a Complete Scheme for Tabled Execution Based on Program Transformation
Tabled evaluation has proved to be an effective method to improve several aspects of goal-oriented query evaluation, including termination and complexity. “Native” implementations of tabled evaluation offer good performance, but also require significant implementation effort, affecting compiler and abstract machine. Alternatively, program transformation-based implementations, such as the original continuation call (CCall) technique, offer lower implementation burden at some efficiency cost. A limitation of the original CCall proposal is that it limits the interleaving of tabled and non-tabled predicates and thus cannot be used for arbitrary programs. In this work we present an extension of the CCall technique that allows the execution of arbitrary tabled programs, as well as some performance results. Our approach offers a useful tradeoff that can be competitive with state-of-the-art implementations, while keeping implementation effort relatively low
Tabling with Sound Answer Subsumption
Tabling is a powerful resolution mechanism for logic programs that captures
their least fixed point semantics more faithfully than plain Prolog. In many
tabling applications, we are not interested in the set of all answers to a
goal, but only require an aggregation of those answers. Several works have
studied efficient techniques, such as lattice-based answer subsumption and
mode-directed tabling, to do so for various forms of aggregation.
While much attention has been paid to expressivity and efficient
implementation of the different approaches, soundness has not been considered.
This paper shows that the different implementations indeed fail to produce
least fixed points for some programs. As a remedy, we provide a formal
framework that generalises the existing approaches and we establish a soundness
criterion that explains for which programs the approach is sound.
This article is under consideration for acceptance in TPLP.Comment: Paper presented at the 32nd International Conference on Logic
Programming (ICLP 2016), New York City, USA, 16-21 October 2016, 15 pages,
LaTeX, 0 PDF figure
An Overview of Ciao and its uses of DataLog for Program Analysis and Optimization
-Objectives:
•Next-generation, high-level, multiparadigm programming language: Ciao.
•Program development environments which perform, as part of compilation:
Verification / debugging(i.e., detect bugs and offer guarantees of safety, reliability, and efficiency.)
Optimization (optimized compilation, parallelization, ...)Using throughout techniques that are at the same time rigorous and practical.
•Apply in a real system, with users –reality check!
•Support also mainstream languages (e.g., Java / Java bytecode).
- Several uses of Datalog and related techniques
Towards a Complete Scheme for Tabled Execution Based on Program Transformation
The advantages of tabled evaluation regarding program termination and reduction of complexity are well known —as are the significant implementation, portability, and maintenance efforts that some proposals (especially those based on suspension) require. This implementation effort is reduced by program transformation-based continuation call techniques, at some efficiency cost. However, the traditional formulation of this proposal [1] limits the interleaving of tabled and non-tabled predicates and thus cannot be used as-is for arbitrary programs. In this paper we present a complete translation for the continuation call technique which, while requiring the same runtime support as the traditional approach, solves these problems and makes it possible to execute arbitrary tabled programs. We also present performance results which show that the resulting CCall approach offers a useful tradeoff that can be competitive with other state-of-the-art implementation
An overview of the ciao multiparadigm language and program development environment and its design philosophy
We describe some of the novel aspects and motivations behind
the design and implementation of the Ciao multiparadigm programming system. An important aspect of Ciao is that it provides the programmer with a large number of useful features from different programming paradigms and styles, and that the use of each of these features can be turned on and off at will for each program module. Thus, a given module may be using e.g. higher order functions and constraints, while another module may be using objects, predicates, and concurrency. Furthermore, the language is designed to be extensible in a simple and modular way. Another important aspect of Ciao is its programming environment, which provides a powerful preprocessor (with an associated assertion language) capable of statically finding non-trivial bugs, verifying that programs comply with specifications, and performing many types of program optimizations. Such optimizations produce code that is highly competitive with other dynamic languages or, when the highest levéis of optimization are used, even that of static languages, all while retaining the interactive development environment of a dynamic language. The environment also includes a powerful auto-documenter. The paper provides an informal overview of the language and program development environment. It aims at illustrating the design philosophy rather than at being exhaustive, which would be impossible in the format of a paper, pointing instead to the existing literature on the system
Bridge transformation for continuation call-based tabled execution.
The advantages of tabled evaluation regarding program termination and reduction of complexity are well known —as are the significant implementation, portability, and maintenance efforts that some proposals (especially those based on suspension) require. This implementation effort is reduced by program transformation-based continuation call techniques, at some efficiency cost. However, the traditional formulation of this proposal by Ramesh and Cheng limits the interleaving of tabled and non-tabled predicates and thus cannot be used as-is for arbitrary programs. In this paper we present a complete translation for the continuation call technique which, using the runtime support needed for the traditional proposal, solves these problems and makes it possible to execute arbitrary tabled programs. We present performance results which show that CCall offers a useful tradeoff that can be competitive
with state-of-the-art implementations
A Program Transformation for Continuation Call-Based Tabled Execution
The advantages of tabled evaluation regarding program termination and
reduction of complexity are well known --as are the significant implementation,
portability, and maintenance efforts that some proposals (especially those
based on suspension) require. This implementation effort is reduced by program
transformation-based continuation call techniques, at some efficiency cost.
However, the traditional formulation of this proposal by Ramesh and Cheng
limits the interleaving of tabled and non-tabled predicates and thus cannot be
used as-is for arbitrary programs. In this paper we present a complete
translation for the continuation call technique which, using the runtime
support needed for the traditional proposal, solves these problems and makes it
possible to execute arbitrary tabled programs. We present performance results
which show that CCall offers a useful tradeoff that can be competitive with
state-of-the-art implementations.Comment: Part of the proceedings of CICLOPS 200