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Publications

Publications by CRACS

2001

Fine-grained multithreading with process calculi

Authors
Lopes, L; Vasconcelos, VT; Silva, F;

Publication
IEEE TRANSACTIONS ON COMPUTERS

Abstract
This paper presents a multithreaded abstract machine for the TyCO process calculus. We argue that process calculi provide a powerful framework to reason about fine-grained parallel computations. They allow for the construction of formally verifiable systems on which to base high-level programming idioms, combined with efficient compilation schemes into multithreaded architectures.

2001

Parallel Implementation of Decision Tree Learning Algorithms

Authors
Amado, N; Gama, J; Silva, FMA;

Publication
Progress in Artificial Intelligence, Knowledge Extraction, Multi-agent Systems, Logic Programming and Constraint Solving, 10th Portuguese Conference on Artificial Intelligence, EPIA 2001, Porto, Portugal, December 17-20, 2001, Proceedings

Abstract
In the fields of data mining and machine learning the amount of data available for building classifiers is growing very fast. Therefore, there is a great need for algorithms that are capable of building classifiers from very-large datasets and, simultaneously, being computationally efficient and scalable. One possible solution is to employ parallelism to reduce the amount of time spent in building classifiers from very-large datasets and keeping the classification accuracy. This work first overviews some strategies for implementing decision tree construction algorithms in parallel based on techniques such as task parallelism, data parallelism and hybrid parallelism. We then describe a new parallel implementation of the C4.5 decision tree construction algorithm. Even though the implementation of the algorithm is still in final development phase, we present some experimental results that can be used to predict the expected behavior of the algorithm. © Springer-Verlag Berlin Heidelberg 2001.

2001

Understanding Memory Management in Prolog Systems

Authors
Castro, LF; Costa, VS;

Publication
Logic Programming, 17th International Conference, ICLP 2001, Paphos, Cyprus, November 26 - December 1, 2001, Proceedings

Abstract

2000

A concurrent programming environment with support for distributed computations and code mobility

Authors
Lopes, L; Figueira, A; Silva, F; Vasconcelos, VT;

Publication
CLUSTER 2000: IEEE INTERNATIONAL CONFERENCE ON CLUSTER COMPUTING, PROCEEDINGS

Abstract
We propose a programming model for distributed concurrent systems with mobile objects in the context of a process calculus. Code mobility is induced by lexical scoping on names. Objects and messages migrate towards the site where their prefixes are lexically bound. Class definitions, on the other hand, are downloaded from the site where they are defined and are instantiated locally upon arrival. We provide several programming examples to demonstrate the expressiveness of the model. Finally, based on this model we describe an. architecture for a run-time system supporting concurrent, distributed computations and code mobility.

2000

Fine grained multithreading with process calculi

Authors
Lopes, L; Silva, F; Vasconcelos, VT;

Publication
2000 INTERNATIONAL CONFERENCE ON PARALLEL ARCHITECTURES AND COMPILATION TECHNIQUES, PROCEEDINGS

Abstract
This paper presents a multithreaded abstract machine for the TyCO process calculus. We argue that process calculi provide a powerful framework to reason about fine grained parallel computations. They allow the construction of formally verifiable systems on which to base high-level programming idioms, combined with efficient compilation schemes into multithreaded architectures.

2000

Novel models for or-parallel logic programs: A performance analysis

Authors
Costa, VS; Rocha, R; Silva, F;

Publication
EURO-PAR 2000 PARALLEL PROCESSING, PROCEEDINGS

Abstract
One of the advantages of logic programming is the fact that it offers many sources of implicit parallelism, such as and-parallelism and or-parallelism. Arguably, or-parallel systems, such as Aurora and Muse, have been the most successful parallel logic programming systems so far. Or-parallel systems rely on techniques such as Environment Copying to address the problem that branches being explored in parallel may need to assign different bindings for the same shared variable. Recent research has led to two new binding representation approaches that also support independent and-parallelism: the Sparse Binding Array and the Copy-On-Write binding models. In this paper, we investigate whether these newer models are practical alternatives to copying for or-parallelism. We based our work on YapOr, an or-parallel copying system using the YAP Prolog engine, so that the three alternative systems share schedulers and the underlying engine.

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