Wise Objects for Calm Technology

International audienceIn this position paper we identify the design of “wise systems” as an open research problem addressing new technology-based systems. Increasing complexity and sophistication make those systems hard to understand and to master. Human users are very often involved in learning processes that capture all their attention while being of little interest for them. To alleviate human interaction with such systems, as the foundation of our current research, we propose the concept of “wise object” as the building block. Software-based systems would then be able to autonomously learn on themselves and on the way humans use them. Humans would in turn be prompted only when necessary by the system

Byte-Range Asynchronous Locking in Distributed Settings

International audienceThis paper investigate a mutual exclusion algorithm on distributed systems. We introduce a new algorithm based on the Naimi-Trehel algorithm, taking advantage of the distributed approach of Naimi-Trehel while allowing to request partial locks. Such ranged locks offer a semantic close to POSIX file locking, where threads lock some parts of the shared file. We evaluate our algorithm by comparing its performance with to the original Naimi-Trehel algorithm and to a centralized mutual exclusion algorithm. The considered performance metric is the average time to obtain a lock

A Practical Approach of Diffusion Load Balancing Algorithms

In this paper, a practical approach of diffusion load balancing algorithms and its implementation are studied. Three problems are investigated. The first is the determination of the load balancing parameters without any global knowledge. The second problem consists in estimating the cost and the benefit of a load exchange. The last one studies the convergence detection of the load balancing algorithm. For this last point we give an algorithm based on simulated annealing to reduce the convergence towards a load repartition in steps that can be done with discrete loads. Several simulations close this paper and illustrate the impact of the various methods and algorithms introduced

A decentralized convergence detection algorithm for asynchronous parallel iterative algorithms

We introduce a theoretical algorithm and its practical version to perform decentralized detection of the global convergence of parallel asynchronous iterative algorithms. We prove that even if the algorithm is completely decentralized, the detection of global convergence is achieved on one processor under the classical conditions. The proposed algorithm is very useful in the context of grid computing in which the processors are distributed and in which detecting the convergence on a master processor may be penalizing or even impossible as in Peer to Peer computations framework. Finally, the efficiency of the practical algorithm is illustrated in a typical experiment

Analyse de "Time-Lapse" stéréo pour la mesure de déformation 3D, application au suivi du glacier d'Argentière

National audienceL'observation de la Terre par des systèmes d'acquisition d'images permet le suivi des évolutions temporelles d'objets tels que les glaciers, les glissements de terrain, les volcans... Différentes techniques d'observation existent dont la photogrammétrie terrestre qui est en plein essor. Cet article présente une chaîne de traitement adaptée au suivi d'objets géophysiques dans des conditions terrain peu favorables à la photogrammétrie. Les premières étapes sont illustrées sur des séries temporelles d'images stéréoscopiques acquises par deux appareils photo automatiques installés sur la rive droite du glacier d'Argentière afin de reconstruire le relief et mesurer son déplacement en 3D. Les premiers résultats sont validés à travers une expérimentation menée en collaboration avec l'IGN à l'automne 2013

Glacier flow monitoring by digital camera and space-borne SAR images

International audienceMost of the image processing techniques have been first proposed and developed on small size images and progressively applied to larger and larger data sets resulting from new sensors and application requirements. In geosciences, digital cameras and remote sensing images can be used to monitor glaciers and to measure their surface velocity by different techniques. However, the image size and the number of acquisitions to be processed to analyze time series become a critical issue to derive displacement fields by the conventional correlation technique. In this paper, an efficient correlation software is used to compute from optical images the motion of a serac fall and from Synthetic Aperture Radar (SAR) images the motion of Alpine glaciers. The optical images are acquired by a digital camera installed near the Argentière glacier (Chamonix, France) and the SAR images are acquired by the high resolution TerraSAR-X satellite over the Mont-Blanc area. The results illustrate the potential of this software to monitor the glacier flow with camera images acquired every 2 h and with the size of the TerraSAR-X scenes covering 30 × 50 km2

A first comparison of Cosmo-Skymed and TerraSAR-X data over Chamonix Mont-Blanc test-site

International audienceThis paper presents the first results obtained with satellite im- age time series (SITS) acquired by Cosmo-SkyMed (CSK) over the Chamonix Mont-Blanc test-site. A CSK SITS made of 39 images is merged with a TerraSAR-X SITS made of 26 images by using the orbital information and co-registration tools developed in the EFIDIR project. The results are illus- trated by the computation of speckle-free images by temporal averaging, by the generation and comparison of topographic interferograms and by the measure of glacier displacement fields by amplitude correlation

Algorithmique itérative pour l’équilibrage de charge dans les réseaux dynamiques

This thesis studies the problem of load balancing on dynamic networks. A dynamic network can be viewed as a network in which some edges may fail during the execution of an algorithm. The first part introduces a new load balancing algorithm, and it describes the adaptation of first order algorithms to dynamic networks. The second part deals with second order algorithms. We introduce a new constrain for these algorithms, so as to ensure that the load stay positive for the load of a system cannot be negative. Then we give the adaptation of these algorithms to dynamic networks. We illustrate the behavior of the first and second order algorithms with some simulations that bring the impact of the dynamism of networks on load balancing algorithms to the fore. These simulations show that the second order algorithms are more reactive to the dynamism than the first order algorithms. Finally, we have implemented a load balancing algorithm on a real application that solves a partial differential equation. With this experimentation, we describe the different steps of the deployment of a load balancing algorithm.Ce mémoire de thèse s’attache aux problèmes d’équilibrage de charge sur les réseaux dynamiques. Un réseau dynamique est un réseau sur lequel certains liens de communication peuvent être perdus ou surchargés. Dans un premier temps, nous introduisons un nouvel algorithme d’équilibrage de charge, puis nous présentons, l’adaptation aux réseaux dynamiques des algorithmes de premier ordre. Dans un second temps nous nous intéressons aux algorithmes de second ordre. Pour ces derniers, nous définissons une nouvelle contrainte qui garantit la positivité de la charge carla charge d’un système ne peut pas être négative. Suite à cette définition, nous donnons l’adaptation de ces algorithmes aux réseaux dynamiques. Nous illustrons le comportement des deux types d’algorithmes présentés - premier et second ordre - par différentes simulations qui mettent en évidence l’impact du dynamisme du réseau sur leur évolution. Ces simulations nous montrent que les algorithmes de second ordre sont nettement plus sensibles que ceux de premier ordre. Pour finir ce mémoire, une mise en pratique d’un algorithme d’équilibrage de charge sur un problème concret - la résolution d’une équation différentielle partielle - détaille les différentes étapes nécessaires au déploiement d’un algorithme d’équilibrage de charge

A Practical Approach of Diffusion Load Balancing Algorithms

In this paper, a practical approach of diffusion load balancing algorithms and its implementation are studied. Three problems are investigated. The first one is the determination of the load balancing parameters without any global knowledge. The second problem consists in estimating the cost and the benefit of a load exchange. The last one studies the convergence detection of the load balancing algorithm. For this last point we give an algorithm based on simulated annealing to reduce the convergence towards a load repartition in steps that can be done with discrete loads. Several simulations close this paper and illustrate the impact of the various methods and algorithms introduced