Fernando Silva

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Fernando Silva

Universidade do Porto

Universidad Politécnica de Madrid

Salvador Abreu

Universidade de Évora

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Papers by Fernando Silva

Or-parallelism within tabling

Practical Aspects of Declarative Languages, 1998

One important advantage of logic programming is that it allows the implicit exploitation of paral... more One important advantage of logic programming is that it allows the implicit exploitation of parallelism. Towards this goal, we suggest that or-parallelism can be efficiently exploited in tabling systems and propose two alternative approaches, Or-Parallelism within Tabling (OPT) and Tabling within Or-Parallelism (TOP). We concentrate on the fundamental concepts of an environment copying based model to implement the OPT approach and introduce the data structures and algorithms necessary to extend the YapOr Or-Parallel system, in order to obtain a parallel tabling system.

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Or-Parallel Prolog on Distributed Shared-Memory Architectures

Implementations of Logic Programming Systems, 1994

Abstract. Dorpp is a prototype or-parallel Prolog system that has been implemented on a distribut... more Abstract. Dorpp is a prototype or-parallel Prolog system that has been implemented on a distributed shared memory machine such as the EDS parallel machine. Dorpp uses a shared binding environment model based on the SRI model. It attempts, however, at exploiting locality and at reducing communication overheads through scheduling and by caching accesses to remote shared data.

Dispepsia: caracterização e abordagem

Revista de Medicina, 2008

Silva FM. Dispepsia: caracterização e abordagem. Rev Med (São Paulo). 2008 out.dez.;87(4):213-23.

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Editorial

Revista de Medicina, 2008

Speeding up Backpropagation

Advanced Neural Computers, 1990

On Applying Or-Parallelism and Tabling to Logic Programs

Computing Research Repository, 2003

Preliminary results indicate that the mechanisms proposed to parallelize search in the context of... more Preliminary results indicate that the mechanisms proposed to parallelize search in the context of SLD resolution can indeed be effectively and naturally generalized to parallelize tabled computations, and that the resulting systems can achieve good performance on shared-memory parallel machines. More importantly, it emphasizes our belief that through applying or-parallelism and tabling to logic programs the range of applications for Logic Programming can be increased.

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On a Tabling Engine That Can Exploit Or-Parallelism

International Conference on Logic Programming/Joint International Conference and Symposium on Logic Programming, 2001

Tabling is an implementation technique that improves the declarativeness and expressiveness of Pr... more Tabling is an implementation technique that improves the declarativeness and expressiveness of Prolog by reusing solutions to goals. Quite a few interesting applications of tabling have been developed in the last few years, andsev eral are by nature non-deterministic. This raises the question of whether parallel search techniques can be usedto improve the performance of tabled applications. In this work we demonstrate that the mechanisms proposed to parallelize search in the context of SLD resolution naturally generalize to parallel tabledcomputations, and that resulting systems can achieve goodp erformance on multi-processors. To do so, we present the OPTYap parallel engine. In our system individual SLG engines communicate data through stack copying. Completion is detected through a novel parallel completion algorithm that builds upon the data structures proposed for or-parallelism. Scheduling is simplified by building on previous research on or-parallelism. We show initial performance results for our implementation. Our best result is for an actual application, model checking, where we obtain linear speedups.

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On Applying Or-Parallelism and Tabling to Logic Programs

Theory and Practice of Logic Programming, 2005

Logic Programming languages, such as Prolog, provide a high-level, declarative approach to progra... more Logic Programming languages, such as Prolog, provide a high-level, declarative approach to programming. Logic Programming offers great potential for implicit parallelism, thus allowing parallel systems to often reduce a program's execution time without programmer intervention. We believe that for complex applications that take several hours, if not days, to return an answer, even limited speedups from parallel execution can directly translate to very significant productivity gains.

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Variable-frequency synthesis: An improved harmonic coding scheme

International Conference on Acoustics, Speech, and Signal Processing, 1984

The Harmonic Coding concept has already shown its potential for efficiently coding speech. Previo... more The Harmonic Coding concept has already shown its potential for efficiently coding speech. Previous implementations have usec a frame rate of one every 16 ms. This was mainly due to the fact that, with longer frames, even a nonstationary spectral model (of low order) cannot reproduce the zones of fast-varying pitch with the desirable quality. However, the high framing rate

Acceleration Techniques for the Backpropagation Algorithm

EURASIP Workshop, 1990

Like other gradient descent techniques, backpropagation converges slowly, even for medium sized n... more Like other gradient descent techniques, backpropagation converges slowly, even for medium sized network problems. This fact results from the usually large dimension of the weight space and from the particular shape of the error surface in each iteration point. Oscillation between the sides of deep and narrow valleys, for example, is a well known case where gradient descent provides poor convergence rates. In this work, we present an acceleration technique for the backpropagation algorithm based on individual adaptation of the learning rate parameter of each synapse. The efficiency of the method is discussed and several related issues are analyzed.

Or-parallelism within tabling

Practical Aspects of Declarative Languages, 1998

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Or-Parallel Prolog on Distributed Shared-Memory Architectures

Implementations of Logic Programming Systems, 1994