A framework for proving the self-organization of dynamic systems

This paper aims at providing a rigorous definition of self- organization, one of the most desired properties for dynamic systems (e.g., peer-to-peer systems, sensor networks, cooperative robotics, or ad-hoc networks). We characterize different classes of self-organization through liveness and safety properties that both capture information re- garding the system entropy. We illustrate these classes through study cases. The first ones are two representative P2P overlays (CAN and Pas- try) and the others are specific implementations of \Omega (the leader oracle) and one-shot query abstractions for dynamic settings. Our study aims at understanding the limits and respective power of existing self-organized protocols and lays the basis of designing robust algorithm for dynamic systems

Online regenerator placement.

Connections between nodes in optical networks are realized by lightpaths. Due to the decay of the signal, a regenerator has to be placed on every lightpath after at most d hops, for some given positive integer d. A regenerator can serve only one lightpath. The placement of regenerators has become an active area of research during recent years, and various optimization problems have been studied. The first such problem is the Regeneration Location Problem (Rlp), where the goal is to place the regenerators so as to minimize the total number of nodes containing them. We consider two extreme cases of online Rlp regarding the value of d and the number k of regenerators that can be used in any single node. (1) d is arbitrary and k unbounded. In this case a feasible solution always exists. We show an O(log|X| ·logd)-competitive randomized algorithm for any network topology, where X is the set of paths of length d. The algorithm can be made deterministic in some cases. We show a deterministic lower bound of W([(log(|E|/d) ·logd)/(log(log(|E|/d) ·logd))])log(Ed)logdlog(log(Ed)logd) , where E is the edge set. (2) d = 2 and k = 1. In this case there is not necessarily a solution for a given input. We distinguish between feasible inputs (for which there is a solution) and infeasible ones. In the latter case, the objective is to satisfy the maximum number of lightpaths. For a path topology we show a lower bound of Öl/2l2 for the competitive ratio (where l is the number of internal nodes of the longest lightpath) on infeasible inputs, and a tight bound of 3 for the competitive ratio on feasible inputs

Lo comúncomo factor de resiliencia local: entre referentes y actividades.El caso de la comunidad de Capulálpam de Méndez en México

Este documento de trabajo se basa en una tesis de maestría en geografía humana realisada en la UQAM entre 2010 y 2013, titulada Comunidad y resistencia: el manejo comunitario de los recursos naturales frente a la globalización neoliberal: el caso de Capulálpam de Méndez, Oaxaca, México(, en francés).En un inicio fue pensado como una síntesisde ésta, pero la idea original dio un giro al considerar otros elementos teóricos presentes en determinadas líneas de investigación en las que se ha querido profundizar.El autor desea agradecer a la Universidad de la Sierra Juárez (UNSIJ) por su apoyo durante el trabajo de campo, especialmente a los investigadores Yuri Quiroz Ortuño y Mario Enrique Fuente Carrasco.Ce texte se penche sur les pratiques instituantes développées par le village de Capulálpam de Méndez situé dans l’État de Oaxaca au Mexique. À partir d’un système de gouvernance communale hérité à la fois de la Révolution mexicaine et de la réforme agraire qu’elle a engendrée, mais aussi de pratiques ancestrales encore plus vieilles, cette communauté de la Sierra Juárez a mis sur pied plusieurs instances et entreprises collectivesqui l’ont dynamisée. Nous décrivons dans ce texte le modede fonctionnement du système de charge et la façon dont le développement a y été articulé dans le village. À l’aide des concepts d’institutions et de commun, nous dégageons la particularité du mode de développement de Capulálpam qui a résistéaux avancée de la normativité néolibérales promues par les réformes des quatre dernières décennies dont l’échelon national mexicain n’a pas échappé.El presente texto examina lasprácticas comunitarias instituidas por la población de Capulálpam de Méndez ubicada en el estado de Oaxaca, en México. A partir de un sistema de gobernanza comunal heredada de la Revolución Mexicana ‒y de la reforma agraria producto de ésta‒, así como de prácticas ancestrales arraigadas, esta comunidad de la Sierra de Juárez estableció varios instancias de gobernanza y emprendimientos colectivos que la dinamizaron en diversos aspectos. El texto describe la forma como esta comunidad concibió e incorporó ensu seno el desarrollo, a la vez que da a conocer generalidades del sistema de cargos, característico de su organización. Con la ayuda de conceptos sobre institucionesy lo común, se identificó la particularidad del modo de desarrollo de Capulálpam, cuya población resistió al avance de la normatividad neoliberal promovida por las reformas de las últimas cuatro décadas, avance del cual el Estado mexicano no ha sido ajeno

Mixed Critical Automotive Embedded Applications on Multicores: A Safe Scheduling Approach for Dependability

International audienceMemory access durations on multicore architectures are highly variable, since concurrent accesses to memory by different cores induce time interferences. Consequently, critical software tasks may be delayed by noncritical ones, leading to deadline misses and possible catastrophic failures. We present an approach to tackle the implementation of mixed criticality workloads on multicore chips, focusing on task chains, i.e., sequences of tasks with end-to-end deadlines. Our main contribution is a Monitoring & Control System able to stop noncritical software execution in order to prevent memory interference and guarantee that critical tasks deadlines are met. This paper describes our approach, and the associated experimental framework to conduct experiments to analyze attainable real-time guarantees on a multicore platform

Run-time Control to Increase Task Parallelism in Mixed-Critical Systems

International audienceAlthough multi/many-core platforms enable the parallel execution of tasks, the sharing of resources may lead to long WCETs that fail to meet the real-time constraints of the system. Then, a safe solution is the execution of the most critical tasks in isolation followed by the execution of the remaining tasks. To improve the system performance, we propose an approach where a critical task can run in parallel with less critical tasks, as long as the real-time constraints are met. When no further interferences can be tolerated, the proposed run-time control suspends the low critical tasks until the termination of the critical task. In this paper, we describe the design and prove the correctness of our approach. To do so, a graph grammar is defined to formally model the critical task as a set of control flow graphs on which a safe partial WCET analysis is applied and used at run-time to control the safe execution of the critical task

Estimation of the Order of Non-Parametric Hidden Markov Models using the Singular Values of an Integral Operator

We are interested in assessing the order of a finite-state Hidden Markov Model (HMM) with the only two assumptions that the transition matrix of the latent Markov chain has full rank and that the density functions of the emission distributions are linearly independent. We introduce a new procedure for estimating this order by investigating the rank of some well-chosen integral operator which relies on the distribution of a pair of consecutive observations. This method circumvents the usual limits of the spectral method when it is used for estimating the order of an HMM: it avoids the choice of the basis functions; it does not require any knowledge of an upper-bound on the order of the HMM (for the spectral method, such an upper-bound is defined by the number of basis functions); it permits to easily handle different types of data (including continuous data, circular data or multivariate continuous data) with a suitable choice of kernel. The method relies on the fact that the order of the HMM can be identified from the distribution of a pair of consecutive observations and that this order is equal to the rank of some integral operator (\emph{i.e.} the number of its singular values that are non-zero). Since only the empirical counter-part of the singular values of the operator can be obtained, we propose a data-driven thresholding procedure. An upper-bound on the probability of overestimating the order of the HMM is established. Moreover, sufficient conditions on the bandwidth used for kernel density estimation and on the threshold are stated to obtain the consistency of the estimator of the order of the HMM. The procedure is easily implemented since the values of all the tuning parameters are determined by the sample size