Performance Analysis of Publish/Subscribe Systems

The Desktop Grid offers solutions to overcome several challenges and to answer increasingly needs of scientific computing. Its technology consists mainly in exploiting resources, geographically dispersed, to treat complex applications needing big power of calculation and/or important storage capacity. However, as resources number increases, the need for scalability, self-organisation, dynamic reconfigurations, decentralisation and performance becomes more and more essential. Since such properties are exhibited by P2P systems, the convergence of grid computing and P2P computing seems natural. In this context, this paper evaluates the scalability and performance of P2P tools for discovering and registering services. Three protocols are used for this purpose: Bonjour, Avahi and Free-Pastry. We have studied the behaviour of theses protocols related to two criteria: the elapsed time for registrations services and the needed time to discover new services. Our aim is to analyse these results in order to choose the best protocol we can use in order to create a decentralised middleware for desktop grid

Study of the NP-completeness of the compact table problem

ISBN 978-5-94057-377-7International audienceThe problem of compact tables is to maximise the overlap when building a word that is to include permutations of every given words (all the words being the same length). This problem is shown to be NP-complete in the general case, and some specific restrictions are studied

How to simulate turing machines by invertible onedimensional cellular automata

The issue of testing invertibility of cellular automata has been often discussed. Constructing invertible automata is very useful for simulating invertible dynamical systems, based on local rules. The computation universality of cellular automata has long been positively resolved, and by showing that any cellular automaton could be simulated by an invertible one having a superior dimension, Toffoli proved that invertible cellular automaton of dimension d ≥ 2 were computation-universal. Morita proved that any invertible Turing Machine could be simulated by a one-dimensional invertible cellular automaton, which proved computation-universality of invertible cellular automata. This article shows how to simulate any Turing Machine by an invertible cellular automaton with no loss of time and gives, as a corollary, an easier proof of this result

Introduction à la théorie algorithmique de l'information

We explain the basics of the theory of the Kolmogorov complexity}, also known as algorithmic information theory, and underline the main differences between the Kolmogorov complexity and Kolmogorov prefix complexity. Then, we introduce the definition of randomness for either finite or infinite words according to P. Martin-Löf and show that it is equivalent to the notion of uncompressibility defined via Kolmogorov complexity.Nous expliquons les bases de la théorie de la complexité de Kolmogorov ou théorie algorithmique de l'information. On analyse en particulier les différences et les ressemblances entre la complexité de Kolmogorov et sa variante dite complexité préfixe. Ensuite, nous introduisons une définition d'un mot aléatoire (finie ou infinie), celle de Martin-Löf et montrons qu'elle est équivalente à la notion d'incompressibilité définie via la complexité de Kolmogorov