Papers by flavien vernier
In this paper, first order diffusion load balancing algorithms for totally dynamic networks are i... more In this paper, first order diffusion load balancing algorithms for totally dynamic networks are investigated. Totally dynamic networks are networks in which the topology may change dynamically. Some edges or nodes can appear, disappear or move during the time. In our previous works on dynamic networks, the dynamism was limited to the edges. The main result of this study consists in proving that the load balancing algorithms reduce the unbalance on arbitrary dynamic networks. Notice that the hypotheses of our result are realistic and that for example the network does not have to be maintained connected. To study the behavior of these algorithms, we compare the load evolution by several simulations. load balancing, totally dynamic networks, iterative algorithm.
Journal of Parallel and Distributed Computing, Nov 1, 2005
In this paper, three distributed load balancing algorithms for dynamic networks are investigated.... more In this paper, three distributed load balancing algorithms for dynamic networks are investigated. Dynamic networks are networks in which the topology may change dynamically. The definition of a dynamic network is introduced and its graph model is presented. The main result of this study consists in proving the convergence toward the uniform load distribution of the diffusion algorithm on an arbitrary dynamic network despite communication link failures. We also give two adaptations of this algorithm (the GAE and the relaxed diffusion). Notice that the hypotheses of our result are realistic and that for example the network does not have to be maintained connected. To study the behavior of these algorithms, we compare the load evolution by several simulations.
Synchronous Load Balancing on Asynchronous Iterative Computation
Journal of Algorithms & Computational Technology, Mar 1, 2009
Asynchronisme et équilibrage de charge dans la grille de calcul
HAL (Le Centre pour la Communication Scientifique Directe), Dec 1, 2002
In Ecole d'hiver GRID 2002, Aussois, Franc
Internet of Things (IoT) technologies remain young and require software technologies to ensure da... more Internet of Things (IoT) technologies remain young and require software technologies to ensure data/information management among things in order to deliver more sophisticated services to their users. In particular, users of IOT-based technologies need systems adapt to their use and not the reverse. To meet those requirements, we enriched our object oriented framework WOF (Wise Object Framework) with a communication structure to interconnect WOs (Wise Objects) and IoT. Things from IoT are then able to learn, monitor and analyze data in order to be able to adapt their behavior. In this paper, we recall the underlying concepts of our framework and then focus on the interconnection between WOs and IoT. This is provided through a software bus-based architecture and IoT related communication protocols. We designed a dedicated communication protocol for IoT objects. We show how IoT objects can benefit from learning, monitoring and analysis mechanisms provided by WOF to identify common usage of a system and unusual behavior (habit change). We illustrate this through a particular case of home automation.
An overview to remotely sensed displacement measurements fusion: Current status and challenges
2016 IEEE International Geoscience and Remote Sensing Symposium (IGARSS), 2016
At the end of the 20th century, the development of spatial geodetic techniques (optical & SAR... more At the end of the 20th century, the development of spatial geodetic techniques (optical & SAR imagery, GPS) has allowed for drastic improvement of the spatial coverage and the resolution of the displacement measurements. The arrival of these techniques has caused an effective revolution by significantly improving our ability to measure the ground movement, as well as their temporal evolutions with great precision over large areas. Spectacular results have been obtained in numerous applications with displacement of various characteristics (in terms of magnitude, duration, spatial distribution): the study of subsidence in urban areas, of the co-seismic, inter-seismic and post-seismic motions, of glacier flows, of volcanic deformation, etc. Nowadays, the displacement maps obtained by remote sensing techniques cover almost the whole world, with a precision within millimetres per year. Therefore, they are considered as the predominant sources for studies of the terrestrial deformation, from which geophysical models of the deformation have been retrieved to further understand the deformation source in depth. To this end, good knowledge of the reliability of the remote sensing data, as well as of the physical models accordingly obtained is crucial for all the researches and applications that use these sources of information. A perspective of significant improvement in the accuracy of the displacement measurement appears with the growing availability of remote sensing data. Methodological development in fusion of displacement measurements and of the integration of a physical model based on the supercomputer facilities seems necessary to reduce the uncertainty and to improve the accuracy of the displacement measurement. In this context, this paper addresses the current status, challenges and perspectives of the remotely sensed displacement measurement fusion.
Algorithmique itérative pour l'équilibrage de charge dans les réseaux dynamiques. (Iterative algorithm for load balancing on dynamic networks)
Ce memoire de these s'attache aux problemes d'equilibrage de charge sur les reseaux dynam... more Ce memoire de these s'attache aux problemes d'equilibrage de charge sur les reseaux dynamiques. Un reseau dynamique est un reseau sur lequel certains liens de communication peuvent etre perdus ou surcharges. Dans un premier temps, nous introduisons un nouvel algorithme d'equilibrage de charge, puis nous presentons, l'adaptation aux reseaux dynamiques desalgorithmes de premier ordre. Dans un second temps nous nous interessons aux algorithmes de second ordre. Pour ces derniers, nous definissons une nouvelle contrainte qui garantit la positivite de la charge car la charge d'un systeme ne peut pas etre negative. Suite a cette definition, nous donnons l'adaptation de ces algorithmes aux reseaux dynamiques. Nous illustrons le comportement des deux types d'algorithmes presentes - premier et second ordre - par differentes simulations qui mettent en evidence l'impact du dynamisme du reseau sur leur evolution. Ces simulations nous montrent que les algorithmes d...
A New Software Architecture for the Wise Object Framework: Multidimensional Separation of Concerns
Proceedings of the 17th International Conference on Software Technologies
International audienceLarge-scale distributed systems are highly dynamic: nodes may crash, messag... more International audienceLarge-scale distributed systems are highly dynamic: nodes may crash, messages may be delayed or lost, new nodes may join, virtual machines may migrate... The workload may also vary a lot depending on the users or applications behavior. Thus, distributed systems and services must adapt continuously in order to remain efficient. To do so, distributed systems usually monitor their environment and maintain a knowledge of what has happened (e.g., heartbeats time-stamps for a failure detection mechanism, data access statistics for a distributed storage systems, etc.). Based on these observations, a distributed system can decide to adapt to better tackle future situations (migrate a virtual machine, create a new data replica, etc.). However, even if a system has a full event log, it is not a trivial task to decide how much and which part of the past must be taken into account. In this paper we propose and study the impact of multiple approaches, from "full-memory...
Scientific Reports
In the days to weeks following an earthquake, landslides can display specific post-seismic motion... more In the days to weeks following an earthquake, landslides can display specific post-seismic motions, including delayed initiations and post-seismic relaxations. These motions have an uncertain origin, sometimes attributed to specificities of the landslide basal interface or to fluid transports in the landslide basal shear zone. Here we address this question, by documenting the co- and post-seismic motions of slow-moving landslides accelerated by the Gorkha earthquake (Mw 7.8, 25/04/2015, Nepal). We detect 11 slow-moving landslides over an area of 750 km$$^2$$ 2 in the near field of the earthquake, and monitor their motions thanks to a time-series of Pléiades optical satellite images and SAR Sentinel-1 images. The post-seismic landslide motions are much larger than the co-seismic ones, reaching up to $$34 \,\pm\, 0.6$$ 34 ± 0.6 m accommodated over 2 months. A delayed initiation of several days (> 4 days) is also measured for at least two of the landslides. We analyze our findings ...
3D displacement retrieval on a scaled model of mountain slope by virtual multi-view photogrammetry
International audienc
Open Access
Fast correlation technique for glacier flow monitoring by digital camera and space-borne SAR images
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific r... more HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Improving the execution of workflows for SAR image analysis Matthieu Volat, Flavien Vernier, Marie-Pierre Doin, Cécile Lasserre, Emmanuel Trouvé, Erwan Pathier
IEEE Geoscience and Remote Sensing Magazine, 2016
Nowadays, data fusion constitutes the key subject in numerous applications of remotely sensed dis... more Nowadays, data fusion constitutes the key subject in numerous applications of remotely sensed displacement measurements, with the increasing availability of remote sensing data and the requirement of improvement of the measurement accuracy. This paper addresses the current status and challenges in the fusion of remotely sensed displacement measurements. An overview is given to discuss the remote sensing sources and techniques extensively used for displacement measurement and the recent development and achievement of displacement measurements fusion. Fusion between displacement measurements and integration of a geophysical model are discussed. The fusion strategies and uncertainty propagation approaches are illustrated in two main applications: 1) surface displacement measurements fusion to retrieve surface displacement with reduced uncertainty in case of redundancy, with larger spatial extension or of higher level in case of complementarity 2) surface displacement measurements fusion to estimate the geometrical parameters of a physical deformation model in case of redundancy and complementarity. Finally, the current status and challenges of remotely sensed displacement measurements fusion are highlighted. Moreover, some potential ways are proposed to deal with heterogeneous data types and to assimilate remote sensing data into physical models in order to realise near real time displacement monitoring.
IEEE Transactions on Parallel and Distributed Systems, 2005
We introduce a theoretical algorithm and its practical version to perform decentralized detection... more 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.
2019 IEEE 18th International Symposium on Network Computing and Applications (NCA), Sep 1, 2019
Data management has become crucial. Distributed applications and users manipulate large amounts o... more Data management has become crucial. Distributed applications and users manipulate large amounts of data. More and more distributed data management solutions arise, e.g. Casandra or Cosmos DB. Some of them propose multiple consistency protocols. Thus, for each piece of data, the developer or the user can choose a consistency protocol adapted to his needs. In this paper we explain why taking the consistency protocol into account is important while replication (especially placing) pieces of data; and we propose CAnDoR, an approach that dynamically adapts the replication according to the data usage (read/write frequencies and locations) and the consistency protocol used to manage the piece of data. Our simulations show that using CAnDoR to place and move data copies can improve the global average access latency by up to 40%.
De l'exécution distribuée des chaînes de traitements d'images à l'acquisition distribuée de connaissance par les traitements
Most of the image processing techniques have been first proposed and developed on small size imag... more Most 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, the monitoring of glacier evolution by image analysis is expected to provide useful information regarding the local impact of global changes and associated risks in the surrounding areas. Digital cameras or remote sensing images can be used to measure the glacier 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. A fast correlation computation implies an optimization study of a correlation algorithm. This paper describes the mathematical optimization of the classical normalized cross-correlation and its implementation. This implementation overcomes the computation time and windo...
Abstract. In this paper, three distributed load balancing algorithms for dynamic networks are inv... more Abstract. In this paper, three distributed load balancing algorithms for dynamic networks are investigated. Dynamic networks are networks in which the topology may change dynamically. The definition of a dynamic network is introduced and its graph model is presented. The main result of this study consists in proving the convergence toward the uniform load distribution of the diffusion algorithm on an arbitrary dynamic network despite communication link failures. We also give two adaptations of this algorithm (the GAE and the relaxed diffusion). Notice that the hypotheses of our result are realistic and that for example the network does not have to be maintained connected. To study the behavior of these algorithms, we compare the load evolution by several simulations.
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Papers by flavien vernier