13 research outputs found
A Framework for Datatype Transformation
We study one dimension in program evolution, namely the evolution of the
datatype declarations in a program. To this end, a suite of basic
transformation operators is designed. We cover structure-preserving
refactorings, but also structure-extending and -reducing adaptations. Both the
object programs that are subject to datatype transformations, and the meta
programs that encode datatype transformations are functional programs.Comment: Minor revision; now accepted at LDTA 200
A Machine Learning guided Rewriting Approach for ASP Logic Programs
Answer Set Programming (ASP) is a declarative logic formalism that allows to
encode computational problems via logic programs. Despite the declarative
nature of the formalism, some advanced expertise is required, in general, for
designing an ASP encoding that can be efficiently evaluated by an actual ASP
system. A common way for trying to reduce the burden of manually tweaking an
ASP program consists in automatically rewriting the input encoding according to
suitable techniques, for producing alternative, yet semantically equivalent,
ASP programs. However, rewriting does not always grant benefits in terms of
performance; hence, proper means are needed for predicting their effects with
this respect. In this paper we describe an approach based on Machine Learning
(ML) to automatically decide whether to rewrite. In particular, given an ASP
program and a set of input facts, our approach chooses whether and how to
rewrite input rules based on a set of features measuring their structural
properties and domain information. To this end, a Multilayer Perceptrons model
has then been trained to guide the ASP grounder I-DLV on rewriting input rules.
We report and discuss the results of an experimental evaluation over a
prototypical implementation.Comment: In Proceedings ICLP 2020, arXiv:2009.0915
Folding Transformation Rules for Constraint Logic Programs
We consider the folding transformation rule for constraint
logic programs. We propose an algorithm for applying the folding rule in the case where the constraints are linear equations and inequations over the rational or the real numbers. Basically, our algorithm consists in reducing a rule application to the solution of one or more systems
of linear equations and inequations. We also introduce two variants of the folding transformation rule. The first variant combines the folding rule with the clause splitting rule, and the second variant eliminates the existential variables of a clause, that is, those variables which occur in the body of the clause and not in its head. Finally, we present the algorithms for applying these variants of the folding rule
A Narrowing-based Instantiation Rule for Rewriting-based Fold/Unfold Transformations
AbstractIn this paper we show how to transfer some developments done in the field of functionallogic programming (FLP) to a pure functional setting (FP). More exactly, we propose a complete fold/unfold based transformation system for optimizing lazy functional programs. Our main contribution is the definition of a safe instantiation rule which is used to enable effective unfolding steps based on rewriting. Since instantiation has been traditionally considered problematic in FP, we take advantage of previous experiences in the more general setting of FLP where instantiation is naturally embedded into an unfolding rule based on narrowing. Inspired by the so called needed narrowing strategy, our instantiation rule inherits the best properties of this refinement of narrowing. Our proposal optimizes previous approaches (that require more transformation effort) defined in the specialized literature of pure FP by anticipating bindings on unifiers used to instantiate a given program rule and by generating redexes at different positions on instantiated rules in order to enable subsequent unfolding steps. As a consequence, our correct/complete technique avoids redundant rules and preserves the natural structure of programs
Unfolding-based Improvements on Fuzzy Logic Programs
AbstractUnfolding is a semantics-preserving program transformation technique that consists in the expansion of subexpressions of a program using their own definitions. In this paper we define two unfolding-based transformation rules that extend the classical definition of the unfolding rule (for pure logic programs) to a fuzzy logic setting. We use a fuzzy variant of Prolog where each program clause can be interpreted under a different (fuzzy) logic. We adapt the concept of a computation rule, a mapping that selects the subexpression of a goal involved in a computation step, and we prove the independence of the computation rule. We also define a basic transformation system and we demonstrate its strong correctness, that is, original and transformed programs compute the same fuzzy computed answers. Finally, we prove that our transformation rules always produce an improvement in the efficiency of the residual program, by reducing the length of successful Fuzzy SLD-derivations
The Divide-and-Conquer Subgoal-Ordering Algorithm for Speeding up Logic Inference
It is common to view programs as a combination of logic and control: the
logic part defines what the program must do, the control part -- how to do it.
The Logic Programming paradigm was developed with the intention of separating
the logic from the control. Recently, extensive research has been conducted on
automatic generation of control for logic programs. Only a few of these works
considered the issue of automatic generation of control for improving the
efficiency of logic programs. In this paper we present a novel algorithm for
automatic finding of lowest-cost subgoal orderings. The algorithm works using
the divide-and-conquer strategy. The given set of subgoals is partitioned into
smaller sets, based on co-occurrence of free variables. The subsets are ordered
recursively and merged, yielding a provably optimal order. We experimentally
demonstrate the utility of the algorithm by testing it in several domains, and
discuss the possibilities of its cooperation with other existing methods
Rule-based Methodologies for the Specification and Analysis of Complex Computing Systems
Desde los orígenes del hardware y el software hasta la época actual, la complejidad
de los sistemas de cálculo ha supuesto un problema al cual informáticos, ingenieros
y programadores han tenido que enfrentarse. Como resultado de este esfuerzo han
surgido y madurado importantes áreas de investigación. En esta disertación abordamos
algunas de las líneas de investigación actuales relacionada con el análisis y
la verificación de sistemas de computación complejos utilizando métodos formales y
lenguajes de dominio específico.
En esta tesis nos centramos en los sistemas distribuidos, con un especial interés por
los sistemas Web y los sistemas biológicos. La primera parte de la tesis está dedicada
a aspectos de seguridad y técnicas relacionadas, concretamente la certificación del
software. En primer lugar estudiamos sistemas de control de acceso a recursos y proponemos
un lenguaje para especificar políticas de control de acceso que están fuertemente
asociadas a bases de conocimiento y que proporcionan una descripción sensible
a la semántica de los recursos o elementos a los que se accede. También hemos desarrollado
un marco novedoso de trabajo para la Code-Carrying Theory, una metodología
para la certificación del software cuyo objetivo es asegurar el envío seguro de código
en un entorno distribuido. Nuestro marco de trabajo está basado en un sistema de
transformación de teorías de reescritura mediante operaciones de plegado/desplegado.
La segunda parte de esta tesis se concentra en el análisis y la verificación de sistemas
Web y sistemas biológicos. Proponemos un lenguaje para el filtrado de información
que permite la recuperación de informaciones en grandes almacenes de datos. Dicho
lenguaje utiliza información semántica obtenida a partir de ontologías remotas
para re nar el proceso de filtrado. También estudiamos métodos de validación para
comprobar la consistencia de contenidos web con respecto a propiedades sintácticas
y semánticas. Otra de nuestras contribuciones es la propuesta de un lenguaje que
permite definir y comprobar automáticamente restricciones semánticas y sintácticas
en el contenido estático de un sistema Web. Finalmente, también consideramos los
sistemas biológicos y nos centramos en un formalismo basado en lógica de reescritura
para el modelado y el análisis de aspectos cuantitativos de los procesos biológicos.
Para evaluar la efectividad de todas las metodologías propuestas, hemos prestado
especial atención al desarrollo de prototipos que se han implementado utilizando
lenguajes basados en reglas.Baggi ., M. (2010). Rule-based Methodologies for the Specification and Analysis of Complex Computing Systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8964Palanci
AutoPar: automating the parallelization of functional programs
As the pervasiveness of parallel architectures in computing increases, so does the need for efficiently implemented parallel software. However, the development of parallel software is inherently more difficult than that of sequential software and is fraught with many pitfalls, such as race conditions and locking issues, amongst others. Developers are typically more comfortable developing sequentially, yet as the limitations of single-core processor speeds are reached, they have no choice but to reach for parallel implementations to obtain the required performance increases.
An obvious solution to the parallelisation problem is to allow developers to continue to develop sequentially and generate efficient parallel programs automatically from these sequential ones. There are many existing techniques
which automate the parallelisation process, however these techniques place many constraints upon the programs they are applicable to.
This thesis defines a fully automatic parallelisation technique which places no restriction on its input programs and is applicable to programs defined using any data-type. The technique consists of two components: the first allows a given program to be redefined in terms of well-partitioned data. The second then explicitly parallelises the resulting program using Glasgow parallel Haskell.
The technique is applied to several Haskell programs, the results of which have then been benchmarked with respect to the performance of handparallelised versions of the original programs. The benchmarking process has recorded the execution time and parallel performance of each benchmark program. The evaluation of the benchmark results has allowed for the merit of the automated parallelisation technique to be shown