Parallel Chip Firing Game associated with n-cube orientations

We study the cycles generated by the chip firing game associated with n-cube orientations. We show the existence of the cycles generated by parallel evolutions of even lengths from 2 to $2^n$ on $H_n$ (n >= 1), and of odd lengths different from 3 and ranging from 1 to $2^{n-1}-1$ on $H_n$ (n >= 4)

Коротко про авторів

International audienceWe study the effects of a disease affecting a predator on the dynamics of a predator-prey system. We couple an SIRS model applied to the predator population, to a Lotka-Volterra model. The SIRS model describes the spread of the disease in a predator population subdivided into susceptible, infected and removed individuals. The Lotka-Volterra model describes the predator-prey interactions. We consider two time scales, a fast one for the disease and a comparatively slow one for predator-prey interactions and for predator mortality. We use the classical "aggregation method" in order to obtain a reduced equivalent model. We show that there are two possible asymptotic behaviors: either the predator population dies out and the prey tends to its carrying capacity, or the predator and prey coexist. In this latter case, the predator population tends either to a "disease-free" or to a "disease-endemic" state. Moreover, the total predator density in the disease-endemic state is greater than the predator density in the "disease-free" equilibrium (DFE)

Numérotation des graphes sociaux basée sur les communautés pour la réduction des défauts de cache

Last version asked for publication 10th may; finally accepted in 6th April 2017; Accepted after minor changes in 17th October 2016,International audienceABSTRACT. One of social graph's properties is the community structure, that is, subsets where nodes belonging to the same subset have a higher link density between themselves and a low link density with nodes belonging to external subsets. Futhermore, most social network mining algorithms comprise a local exploration of the underlying graph, which consists in referencing nodes in the neighborhood of a particular node. The idea of this paper is to use the community structure during the storage of large graphs that arise in social network mining. The goal is to reduce cache misses and consequently, execution time. After formalizing the problem of social network ordering as a problem of optimal linear arrangement which is known as NP-Complet, we propose NumBaCo, a heuristic based on the community structure. We present for Katz score and Pagerank, simulations that compare classic data structures Bloc and Yale to their corresponding versions that use NumBaCo. Results on a 32 cores NUMA machine using amazon, dblp and web-google datasets show that NumBaCo allows to reduce from 62% to 80% of cache misses and from 15% to 50% of execution time.L'une des propriétés des graphes sociaux est leur structure en communautés, c'est-à-dire en sous-ensembles où les noeuds ont une forte densité de liens entre eux et une faible den-sité de liens avec l'extérieur. Par ailleurs, la plupart des algorithmes de fouille des réseaux sociaux comportent une exploration locale du graphe sous-jacent, ce qui amène à partir d'un noeud, à faire référence aux noeuds situés dans son voisinage. L'idée de cet article est d'exploiter la structure en communautés lors du stockage des grands graphes qui surviennent dans la fouille des réseaux so-ciaux. L'objectif est de réduire le nombre de défauts de cache avec pour conséquence l'amélioration du temps d'exécution. Après avoir formalisé le problème de numérotation des noeuds des réseaux sociaux comme un problème d'arrangement linéaire optimal qui est connu comme NP-Complet, nous proposons NumBaCo, une heuristique basée sur la struture en communautés. Nous présentons pour le score de Katz et Pagerank, des simulations comparant les structures de données classiques Bloc et Yale à leurs versions exploitant NumBaCo. Les résultats obtenus sur une machine NUMA de 32 coeurs à partir des jeux de données amazon, dblp et web-google montrent que NumBaCo contribue à diminuer les défauts de cache de 62% à 80% et le temps d'exécution de 15% à 50%

: QuickFill, QuickMixte: block approaches for reducing the number of programs in program synthesis

International audienceRepetitive tasks are most often tedious; in order to facilitate their execution, program synthesis approaches have been developed. They consist in automatically inferring programs that satisfy the intention of a user. The best known approach in program synthesis is FlashFill integrated into the Excel spreadsheet which allows the processing of character strings. In FlashFill user intent is represented by examples i.e, pairs (input, output). FlashFill explores a very large space of programs and therefore can require a lot of execution time and infer a lot of programs some of which work on given examples but do not capture the user's intent. In this article, we propose two approaches QuickMixte and QuickFill based on blocks which aim to guide the exploration of the program space of FlashFill by enriching the specifications provided by the user. These approaches ask the user to provide associations between subparts of the output and the input to refine the specifications. Experiments carried out on a series of 12 datasets show that QuickMixte and QuickFill make it possible to considerably reduce the program space of FlashFill. We show that with these approaches, it is often possible to give fewer examples than with the original FlashFill algorithm for a larger proportion of correct programs.Keywords : Synthesis of programs, programming by example, manipulation of character strings, repetitive tasks, block approach.Les tâches répétitives sont le plus souvent fastidieuses ; afin de faciliter leur exécution, les approches de synthèse de programmes ont été développées. Elles consistent à inférer automatiquement des programmes qui satisfont l'intention d'un utilisateur. L'approche la plus connue en synthèse de programmes est FlashFill intégrée au tableur Excel qui permet le traitement des chaînes de caractères. Dans FlashFill l'intention de l'utilisateur est représentée par des exemples i.e, des couples (entrée, sortie). FlashFill explore un très grand espace de programmes et peut donc nécessiter un temps d'exécution important et inférer beaucoup de programmes dont certains fonctionnent sur des exemples donnés mais ne capturent pas l'intention de l'utilisateur. Dans cet article, nous proposons deux approches QuickMixte et QuickFill basées sur les blocs qui visent à guider l'exploration de l'espace de programmes de FlashFill en enrichissant les spécifications fournies par l'utilisateur. Ces approches demandent à l'utilisateur de fournir des associations entre les sous-parties de la sortie et de l'entrée pour affiner les spécifications. Les expérimentations menées sur une série de 12 jeux de données montrent que QuickMixte et QuickFill permettent de réduire considérablement l'espace de programmes de FlashFill. Nous montrons qu'avec ces approches, il est souvent possible de donner moins d'exemples qu'avec l'algorithme FlashFill original pour une plus grande proportion de programmes corrects

Node Ranking in Wireless Sensor Networks with Linear Topology

International audienceIn wireless sensor networks with linear topology, knowing the physical order in which nodes are deployed is useful not only for the target application, but also to some network services, like routing or data aggregation. Considering the limited resources of sensor nodes, the design of autonomous protocols to find this order is a challenging topic. In this paper, we propose a distributed and iterative centroid-based algorithm to address this problem. At each iteration, the algorithm selects two virtual anchors and finds the order of a subset of nodes, placed between these two anchors. The proposed algorithm requires local node connectivity knowledge and the identifier of the first sensor node of the network, which is the only manually configured parameter. This solution, scalable and lightweight from the deployment and maintenance point of view, is shown to be robust to connectivity degradation, correctly ordering more than 95% of the nodes, even under very low connectivity condition

WARIM: Wireless Sensor Network Architecture for a Reliable Intersection Monitoring

International audienceA traffic light controller takes as input an estimation of the number of vehicles entering the intersection and produces as output a light plan, with the objective to reduce the traffic jam. The quality of the input traffic estimation is a key consideration on the performance of the traffic light controller. The advent of Wireless Sensor Networks, with their relatively low deployment and operation price, led to the development of several sensor-based architectures for intersection monitoring. We show in this paper that the solutions proposed in the literature are unrealistic in terms of communication possibilities and that they do not allow a measure of the vehicular queue length at a lane level. Based on extensive experimental results, we propose an energy efficient, low cost and lightweight multi-hop wireless sensor network architecture to measure with a good accuracy the vehicle queue length, in order to have a more precise vision of traffic at the intersection. Associated challenges are then discussed, such as self-configuration, routing and energy harvesting, which should be addressed in order to reduce the cost of the proposed solution and to improve the performance of the target application

Node Ranking in Wireless Sensor Networks with Linear Topology

International audienceIn wireless sensor networks with linear topology, knowing the physical order in which nodes are deployed is useful not only for the target application, but also to some network services, like routing or data aggregation. Considering the limited resources of sensor nodes, the design of autonomous protocols to find this order is a challenging topic. In this paper, we propose a distributed and iterative centroid-based algorithm to address this problem. At each iteration, the algorithm selects two virtual anchors and finds the order of a subset of nodes, placed between these two anchors. The proposed algorithm requires local node connectivity knowledge and the identifier of the first sensor node of the network, which is the only manually configured parameter. This solution, scalable and lightweight from the deployment and maintenance point of view, is shown to be robust to connectivity degradation, correctly ordering more than 95% of the nodes, even under very low connectivity condition