WorldCat Identities

Contassot-Vivier, Sylvain

Overview
Works: 18 works in 41 publications in 3 languages and 325 library holdings
Roles: Other, Opponent, Author, Thesis advisor
Publication Timeline
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Most widely held works by Sylvain Contassot-Vivier
Parallel iterative algorithms : from sequential to grid computing by Jacques Mohcine Bahi( Book )

19 editions published between 2007 and 2019 in English and Occitan and held by 301 WorldCat member libraries worldwide

"Focusing on grid computing and asynchronism, Parallel Iterative Algorithms: From Sequential to Grid Computing explores the theoretical and practical aspects of parallel numerical algorithms. Each chapter contains a theoretical discussion of the topic, an algorithmic section that fully details implementation examples and specific algorithms, and an evaluation of the advantages and drawbacks of the algorithms. Several exercises also appear at the end of most chapters." "Providing the theoretical and practical knowledge needed to design and implement efficient parallel iterative algorithms, this book illustrates how to apply these algorithms to solve linear and nonlinear numerical problems in parallel environments, including local, distant, homogeneous, and heterogeneous clusters."--BOOK JACKET
Parallel iterative algorithms by Jacques Mohcine Bahi( Book )

1 edition published in 2007 in English and held by 3 WorldCat member libraries worldwide

"Focusing on grid computing and asynchronism, Parallel Iterative Algorithms: From Sequential to Grid Computing explores the theoretical and practical aspects of parallel numerical algorithms. Each chapter contains a theoretical discussion of the topic, an algorithmic section that fully details implementation examples and specific algorithms, and an evaluation of the advantages and drawbacks of the algorithms. Several exercises also appear at the end of most chapters."
Security analysis of steganalyzers by Yousra Ahmed Fadil( )

2 editions published in 2017 in English and held by 2 WorldCat member libraries worldwide

In the recent time, the field of image steganalysis and steganography became more important due to the development in the Internet domain. It is important to keep in mind that the whole process of steganography and steganalysis can be used for legal or illegal operations like any other applications. The work in this thesis can be divided inthree parts. The first one concentrates on parameters that increase the security of steganography methods against steganalysis techniques. In this contribution the effect of the payload, feature extractions, and group of images that are used in the learning stage and testing stage for the steganalysis system are studied. From simulation, we note that the state of the art steganalyzer fails to detect the presence of a secret message when some parameters are changed. In the second part, we study how the presence of many steganography methods may influence the detection of a secret message. The work takes into consideration that there is no ideal situation to embed a secret message when the steganographier can use any scheme with any payloads. In the third part, we propose a method to compute an accurate distortion map depending on a second order derivative of the image. The second order derivative is used to compute the level curve and to embed the message on pixels outside clean level curves. The results of embedding a secret message with our method demonstrate that the result is acceptable according to state of the art steganography
Digital watermarking for PDF documents and images : security, robustness and AI-based attack by Makram Hatoum( Book )

2 editions published in 2020 in English and held by 2 WorldCat member libraries worldwide

Technological development has its pros and cons. Nowadays, we can easily share, download, and upload digital content using the Internet. Also, malicious users can illegally change, duplicate, and distribute any kind of information, such as images and documents. Therefore, we should protect such contents and arrest the perpetrator. The goal of this thesis is to protect PDF documents and images using the Spread Transform Dither Modulation (STDM), as a digital watermarking technique, while taking into consideration the main requirements of transparency, robustness, and security. STDM watermarking scheme achieved a good level of transparency and robustness against noise attacks. The key to this scheme is the projection vector that aims to spreads the embedded message over a set of cover elements. However, such a key vector can be estimated by unauthorized users using the Blind Source Separation (BSS) techniques. In our first contribution, we present our proposed CAR-STDM (Component Analysis Resistant-STDM) watermarking scheme, which guarantees security while preserving the transparency and robustness against noise attacks. STDM is also affected by the Fixed Gain Attack (FGA). In the second contribution, we present our proposed N-STDM watermarking scheme that resists the FGA attack and enhances the robustness against the Additive White Gaussian Noise (AWGN) attack, JPEG compression attack, and variety of filtering and geometric attacks. Experimentations have been conducted distinctly on PDF documents and images in the spatial domain and frequency domain. Recently, Deep Learning and Neural Networks achieved noticeable development and improvement, especially in image processing, segmentation, and classification. Diverse models such as Convolutional Neural Network (CNN) are exploited for modeling image priors for denoising. CNN has a suitable denoising performance, and it could be harmful to watermarked images. In the third contribution, we present the effect of a Fully Convolutional Neural Network (FCNN), as a denoising attack, on watermarked images. STDM and Spread Spectrum (SS) are used as watermarking schemes to embed the watermarks in the images using several scenarios. This evaluation shows that such type of denoising attack preserves the image quality while breaking the robustness of all evaluated watermarked schemes
Hardware implementation of a pseudo random number generator based on chaotic iteration by Mohammed Bakiri( Book )

2 editions published in 2018 in English and held by 2 WorldCat member libraries worldwide

Security and cryptography are key elements in constrained devices such as IoT, smart card, embedded system, etc. Their hardware implementations represent a challenge in terms of limitations in physical resources, operating speed, memory capacity, etc. In this context, as most protocols rely on the security of a good random number generator, considered an indispensable element in lightweight security core. Therefore, this work proposes new pseudo-random generators based on chaotic iterations, and designed to be deployed on hardware support, namely FPGA or ASIC. These hardware implementations can be described as post-processing on existing generators. They transform a sequence of numbers not uniform into another sequence of numbers uniform. The dependency between input and output has been proven chaotic, according notably to the mathematical definitions of chaos provided by Devaney and Li-Yorke. Following that, we firstly elaborate or develop out a complete state of the art of the material and physical implementations of pseudo-random number generators (PRNG, for pseudorandom number generators). We then propose new generators based on chaotic iterations (IC) which will be tested on our hardware platform. The initial idea was to start from the n-cube (or, in an equivalent way, the vectorial negation in CIs), then remove a Hamiltonian cycle balanced enough to produce new functions to be iterated, for which is added permutation on output . The methods recommended to find good functions, will be detailed, and the whole will be implemented on our FPGA platform. The resulting generators generally have a better statistical profiles than its inputs, while operating at a high speed. Finally, we will implement them on many hardware support (65-nm ASIC circuit and Zynq FPGA platform)
CALCULS PARALLELES POUR LE TRAITEMENT DES IMAGES SATELLITES by Sylvain Contassot-Vivier( Book )

2 editions published in 1998 in French and held by 2 WorldCat member libraries worldwide

L'ETUDE REALISEE DANS CETTE THESE MET EN RELATION DEUX DOMAINES SCIENTIFIQUES A PRIORI DISTINCTS, QUE SONT LA GEOLOGIE ETL'INFORMATIQUE. EN EFFET, LE CONTEXTE DE CE TRAVAIL EST DE CONCEVOIR UNE CHAINE COMPLETE DE TRAITEMENTS PARALLELES SUR LES IMAGES SATELLITES ALLANT DE LA RECONSTRUCTION TRIDIMENSIONNELLE A LA VISUALISATION DES TERRAINS AINSI RECONSTITUES. CE TRAVAIL A FAIT L'OBJET D'UNE COOPERATION ETROITE ENTRE PERSONNES ISSUES DE FORMATIONS AUSSI DIFFERENTES QUE LA GEOLOGIE ET L'INFORMATIQUE. NOUS PROPOSONS D'UNE PART, LA PARALLELISATION D'UN ALGORITHME DE RECONSTRUCTION TRIDIMENSIONNELLE DE RELIEF A PARTIR D'UN COUPLE D'IMAGES SATELLITE. ET D'AUTRE PART, UN ALGORITHME PARALLELE DE VISUALISATION DE TERRAINS AVEC TEXTURE. CES TRAVAUX FONT DONC APPEL A PLUSIEURS DOMAINES DE L'INFORMATIQUE TELS QUE LE PARALLELISME, LA VISION STEREOSCOPIQUE ET LA SYNTHESE D'IMAGES. UNE ETUDE METHODOLOGIQUE PLUS GENERALE SUR LES ALGORITHMES DE TRANSFORMATION GEOMETRIQUE DES IMAGES EST EGALEMENT PRESENTEE. AU NIVEAU SEQUENTIEL, NOUS PROPOSONS POUR CHACUN DES ALGORITHMES ABORDES ET LORSQUE CELA EST PERTINENT, DIFFERENTES OPTIMISATIONS ORIGINALES PERMETTANT DES AMELIORATIONS EN TERMES DE COMPLEXITE ET DONC DE TEMPS DE CALCULS, AINSI QUE DES CHOIX D'OUTILS CALCULATOIRES POUVANT AMELIORER LA QUALITE DES RESULTATS, POINT TRES SENSIBLE DANS UN DOMAINE COMME LA VISION STEREOSCOPIQUE. DANS LE CADRE DU PARALLELISME, NOUS NOUS FOCALISONS SUR LES STRATEGIES DE COMMUNICATIONS ET D'EQUILIBRAGE DES CHARGES POUVANT ETRE MISES EN UVRE POUR TIRER LE MEILLEUR PARTI DES MACHINES PARALLELES. EN COMPARANT NOS PROBLEMES AVEC CEUX DEJA TRAITES DANS LA LITTERATURE, NOUS SOMMES ARRIVES A LA CONCLUSION QU'UN EQUILIBRAGE DES CHARGES DIRIGE PAR LES DONNEES ETAIT PREFERABLE A TOUTE AUTRE TECHNIQUE DANS NOTRE CAS. DE PLUS, QUE L'ON SE PLACE DANS LA PARTIE VISION OU SYNTHESE, L'EQUILIBRAGE DES CHARGES PEUT ETRE ABORDE EXACTEMENT DE LA MEME MANIERE. ON PEUT DONC APPLIQUER LA MEME STRATEGIE SUR CES DIFFERENTS ALGORITHMES. ENFIN, UNE ETUDE THEORIQUE DE LA COMPLEXITE DE L'ALGORITHME PARALLELE DE VISION STEREOSCOPIQUE NOUS PERMET DE DEDUIRE LES POINTS CLES INFLUENCANT LES PERFORMANCES ET DONC D'ESTIMER A PRIORI LE NOMBRE DE PROCESSEURS NECESSAIRES POUR OBTENIR LES MEILLEURES PERFORMANCES ABSOLUES POUR UN ENSEMBLE CONNU DE DONNEES. DES EXPERIMENTATIONS MENEES SUR DIFFERENTES MACHINES PARALLELES, VOLVOX, CRAY T3D OU CRAY T3E NOUS PERMETTENT DE VERIFIER LE BON COMPORTEMENT DE NOS ALGORITHMES PARALLELES ET DE CONFIRMER LEUR EFFICACITE
Ancestral Reconstruction and Investigations of Genomics Recombination on Chloroplasts Genomes by Bashar Al-Nuaimi( )

2 editions published in 2017 in English and held by 2 WorldCat member libraries worldwide

The theory of evolution is based on modern biology. All new species emerge of an existing species. As a result, different species share common ancestry,as represented in the phylogenetic classification. Common ancestry may explainthe similarities between all living organisms, such as general chemistry, cell structure,DNA as genetic material and genetic code. Individuals of one species share the same genes but (usually) different allele sequences of these genes. An individual inheritsalleles of their ancestry or their parents. The goal of phylogenetic studies is to analyzethe changes that occur in different organisms during evolution by identifying therelationships between genomic sequences and determining the ancestral sequences and theirdescendants. A phylogeny study can also estimate the time of divergence betweengroups of organisms that share a common ancestor. Phylogenetic trees are usefulin the fields of biology, such as bioinformatics, for systematic phylogeneticsand comparative. The evolutionary tree or the phylogenetic tree is a branched exposure the relationsevolutionary between various biological organisms or other existence depending on the differences andsimilarities in their genetic characteristics. Phylogenetic trees are built infrom molecular data such as DNA sequences and protein sequences. Ina phylogenetic tree, the nodes represent genomic sequences and are calledtaxonomic units. Each branch connects two adjacent nodes. Each similar sequencewill be a neighbor on the outer branches, and a common internal branch will link them to acommon ancestor. Internal branches are called hypothetical taxonomic units. Thus,Taxonomic units gathered in the tree involve being descended from a common ancestor. Ourresearch conducted in this dissertation focuses on improving evolutionary prototypesappropriate and robust algorithms to solve phylogenetic inference problems andancestral information about the order of genes and DNA data in the evolution of the complete genome, as well astheir applications
Évitabilité de puissances additives en combinatoire des mots by Florian Liétard( )

1 edition published in 2020 in French and held by 1 WorldCat member library worldwide

The present thesis is dedicated to the various aspects of the problem of avoiding additive cubes in the fixed points of morphisms. Problems concerning the avoidability of additive powers are closely related to questions in the theory of semigroups. Since the publication of the article of J. Cassaigne, J.D. Currie, L. Schaeffer and J.O. Shallit (2013) we know that it is possible to construct an infinite word over {0, 1 ,3, 4} that avoids additive cubes, i.e., a word that avoids three consecutive blocks of same size and same sum. We first explain the methods used by the authors in their article, and then use it as a starting point for our discussions, with the ultimate aim to clarify the various similarities and connections between the different morphisms that allow to avoid additive cubes on alphabets over 4 letters. We next discuss our implementation in C++ of the investigation of theses morphisms, and then proceed to give an infinite family of morphisms (corresponding to classes of equivalence) that avoid additive cubes. After this investigation, we give a general proof scheme that is based on substitutions between morphisms. The main result of the thesis is that for any alphabet of 4 letters, with the sole exception of the alphabet {0, 1 ,2, 3} and its affine transformations, there is an explicit morphism whose infinite fixed point avoids additive cubes over the given alphabet. This work has been carried out in collaboration with Matthieu Rosenfeld and gave rise to an article in a peer-reviewed journal. In order to show this result, we use arguments from the article of Cassaigne et al., several numerical estimates for the underlying quantities, case disjunction as well as symmetry considerations for the alphabets under consideration. In the final part of the thesis we then study the question of avoiding additive cubes over {0, 1 ,2, 3} with the hope to answer a question posed by M. Rao and M. Rosenfeld in 2018. This alphabet is the only 4-letters alphabet where our result does not apply. We first study by graphical means the words that contain additive powers, and we discuss and implement in a second step two parallelized computer programs. The first program detects in an efficient way the occurrence of additive powers in very long words, whereas the second one allows to create long words over {0, 1 ,2, 3} without introducing any additive cube. With the help of these programs, we obtain a word of over 70 million letters that avoids additive cubes over {0, 1 ,2, 3}. This largely improves on the former known bound (1.4 x 10^5). To obtain our result, as suggested by our graphical considerations, we periodically reverse the order of priority for the choice of the letters in the construction of our word. Our programs use multi-computers and multi-threads settings to gain considerably on efficiency
Preventing information leakage in NDN with name and flow filters by Daishi Kondo( )

1 edition published in 2018 in English and held by 1 WorldCat member library worldwide

In recent years, Named Data Networking (NDN) has emerged as one of the most promising future networking architectures. To be adopted at Internet scale, NDN needs to resolve the inherent issues of the current Internet. Since information leakage from an enterprise is one of the big issues even in the Internet and it is very crucial to assess the risk before replacing the Internet with NDN completely, this thesis investigates whether a new security threat causing the information leakage can happen in NDN. Assuming that (i) a computer is located in the enterprise network that is based on an NDN architecture, (ii) the computer has already been compromised by suspicious media such as a malicious email, and (iii) the company installs a firewall connected to the NDN-based future Internet, this thesis focuses on a situation that the compromised computer (i.e., malware) attempts to send leaked data to the outside attacker. The contributions of this thesis are fivefold. Firstly, this thesis proposes an information leakage attack through a Data and through an Interest in NDN. Secondly, in order to address the information leakage attack, this thesis proposes an NDN firewall which monitors and processes the NDN traffic coming from the consumers with the whitelist and blacklist. Thirdly, this thesis proposes an NDN name filter to classify a name in the Interest as legitimate or not. The name filter can, indeed, reduce the throughput per Interest, but to ameliorate the speed of this attack, malware can send numerous Interests within a short period of time. Moreover, the malware can even exploit an Interest with an explicit payload in the name (like an HTTP POST message in the Internet), which is out of scope in the proposed name filter and can increase the information leakage throughput by adopting a longer payload. To take traffic flow to the NDN firewall from the consumer into account, fourthly, this thesis proposes an NDN flow monitored at an NDN firewall. Fifthly, in order to deal with the drawbacks of the NDN name filter, this thesis proposes an NDN flow filter to classify a flow as legitimate or not. The performance evaluation shows that the flow filter complements the name filter and greatly chokes the information leakage throughput
Segmentation et mesures géométriques : application aux objets tubulaires métalliques by Nicolas Aubry( )

1 edition published in 2017 in French and held by 1 WorldCat member library worldwide

The presence of specularity on an object is a recurring problem that limits the application of many segmentation methods. Indeed, specularities are areas with a very high intensity and greatly disturb the detection when the notion of gradient of the image is used. The work carried out in this thesis makes it possible to propose a new detection method for a metallic tubular object in an image. The method avoids the notion of gradient by using the notion of intensity profile. We propose in this manuscript a process which traverses predefined rectangular areas of the image by scanning a discrete segment in search of a reference intensity profile. This work is part of a collaboration with Numalliance, a company that manufactures machine tools. This collaboration enables this method to be put into a real industrial application as part of an automatic and real-time quality control system for parts manufactured by machine tools. To this end, the method presented must be fast, robust to the specularities and to the industrial environment while being sufficiently precise to make it possible to conclude on the conformity or not of the part
Detection of tumor-like inclusions embedded within human liver tissue using a short-pulsed near-infrared laser beam: Parallel simulations with radiative transfer equation( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

Abstract: An efficient solution to detect tumor-like inclusions embedded within a human liver tissue model is presented, using illumination by a short-pulsed laser beam. Light propagation was accurately solved using the time-dependent radiative transfer equation, with multithreaded parallel computing. A modified finite volume method based on unstructured grids and the fourth-order Runge-Kutta approach was employed to solve the equation in the (2-D/3-D) spatial and time domains. The normalization technique applied to the Henyey-Greenstein phase function was adopted to ensure numerical stability for values of the anisotropy factor that were close to unity. The presence of one or two circular/spherical inclusions was analyzed from the time and spatially resolved reflectance on the medium bounding surface. The results allowed a minimal size and a maximum distance for the detection of the inclusion to be highlighted. Abstract : Highlights: We detect tumor-like inclusions embedded within a (2D/3D) human liver tissue model. The technique is based on a short-pulsed near-infrared laser beam. We solve the (2D/3D) time-dependent RTE, with multithreaded parallel computing. The presence of one or two circular/spherical inclusions is analyzed. The results allows a minimal size and a maximum distance for the detection
Multi-View Oriented 3D Data Processing by Kun Liu( )

1 edition published in 2015 in English and held by 1 WorldCat member library worldwide

Point cloud refinement and surface reconstruction are two fundamental problems in geometry processing. Most of the existing methods have been targeted at range sensor data and turned out be ill-adapted to multi-view data. In this thesis, two novel methods are proposed respectively for the two problems with special attention to multi-view data. The first method smooths point clouds originating from multi-view reconstruction without impairing the data. The problem is formulated as a nonlinear constrained optimization and addressed as a series of unconstrained optimization problems by means of a barrier method. The second method triangulates point clouds into meshes using an advancing front strategy directed by a sphere packing criterion. The method is algorithmically simple and can produce high-quality meshes efficiently. The experiments on synthetic and real-world data have been conducted as well, which demonstrates the robustness and the efficiency of the methods. The developed methods are suitable for applications which require accurate and consistent position information such photogrammetry and tracking in computer vision
Caractérisation de tissus biologiques par diffusion de la lumière : application au diagnostic du cancer by Ahmad Addoum( )

1 edition published in 2018 in French and held by 1 WorldCat member library worldwide

La Tomographie Optique Diffuse (TOD) est une nouvelle technique d'imagerie médicale permettant de reconstruire les propriétés optiques des tissus biologiques dans le but de détecter des tumeurs cancéreuses. Il s'agit, toutefois, d'un problème inverse mal-posé et sous-déterminé. Le travail de cette thèse s'articule autour de la résolution de ce problème en utilisant l'équation du transfert radiatif comme modèle de propagation de la lumière (modèle direct). L'analyse de sensibilité a montré que le facteur d'anisotropie g de la fonction de phase de Henyey-Greenstein est le paramètre le plus influant sur la sortie du modèle direct suivi du coefficient de diffusion µs puis du coefficient d'absorption µa. Dans un premier temps, un algorithme de Gauss-Newton a été implémenté en utilisant les fonctions de sensibilités. Toutefois, ce dernier ne permet d'estimer qu'un nombre très limité de paramètres optiques (supposés constants en espace). Dans un second temps, un algorithme de Quasi-Newton a été développé pour reconstruire les distributions spatiales des propriétés optiques. Le gradient de la fonction objectif a été calculé efficacement par la méthode adjointe à travers le formalisme de Lagrange avec une approche Multi-fréquences. Les reconstructions sont obtenues à partir des données simulées en surface. Le facteur g est reconstruit comme un nouvel agent de contraste en TOD. Le problème de diaphonie entre µs g a été donc mis en évidence dans cette thèse. Notre algorithme a permis de reconstruire en 2D et 3D une ou plusieurs inclusions tumorales présentant différentes formes. La qualité des images reconstruites a été examinée en fonction du nombre de fréquences, de la diaphonie, du niveau de contraste (Inclusion/Fond), du niveau de bruit et de la position des inclusions tumorales
Positionnement visuel dans un monde d'objets by Vincent Gaudillière( )

1 edition published in 2020 in French and held by 1 WorldCat member library worldwide

La Réalité Augmentée peut être définie comme la superposition de la réalité et d'éléments (sons, images 2D, 3D, vidéos, etc.) calculés par un système informatique en temps réel. En pratique, ce terme désigne l'ajout d'éléments visuels, soit dans le champ de vision d'un observateur par l'intermédiaire de lunettes spécifiques (ex. : Microsoft Hololens, Magic Leap One), soit sur un écran à travers lequel l'observateur voit la réalité (généralement un smartphone ou une tablette). Au cours de ce travail de recherche, nous nous sommes intéressés au déploiement de la Réalité Augmentée dans un contexte industriel, et plus particulièrement aux défis que des environnements industriels de grande taille (usines, centrales, navires) représentent en termes d'analyse et de traitement des images. Nous avons notamment étudié le recours aux objets d'intérêt présents dans la scène pour reconnaître le lieu dans lequel se trouve l'observateur puis calculer sa position précise par rapport à l'environnement. Les applications visées sont, entre autres, l'aide à la fabrication, l'aide à la maintenance, la documentation et la formation. Après avoir proposé une définition fonctionnelle du concept de lieu en environnement industriel, comme zone d'interaction autour d'un objet d'intérêt, nous avons abordé la reconnaissance de lieux comme une tâche de récupération d'images dans laquelle la similarité entre l'image inconnue et les images de référence est mesurée en deux étapes. La validité des images présentant les plus grandes similarités avec l'image inconnue est ensuite évaluée par estimation de la géométrie épipolaire liant l'image inconnue et chacune des images récupérées. La mesure de similarité et l'estimation de la géométrie sont guidées par le calcul de correspondances de niveau objet entre régions d'intérêt des deux images. Pour calculer la pose de la caméra, nous avons ensuite tiré profit des objets d'intérêt présents dans la scène, en utilisant pour cela une modélisation de ces derniers sous forme d'ellipsoïdes, les projections des objets dans l'image étant modélisées sous forme d'ellipses. Nos contributions au problème d'estimation de pose de caméra à partir de correspondances ellipse - ellipsoïde sont d'ordre à la fois théorique et pratique. Nous avons notamment montré qu'il existe une paramétrisation des solutions du problème à un seul ellipsoïde, et, par ailleurs, que le problème d'estimation de pose de caméra peut être réduit à un problème d'estimation de son orientation seulement. Nous avons également proposé une manière robuste de traiter les multiples appariements possibles entre les objets détectés dans l'image et les objets présents dans le modèle 3D de la scène
Automatic code generation and optimization of multi-dimensional stencil computations on distributed-memory architectures by Mariem Saied( )

1 edition published in 2018 in English and held by 1 WorldCat member library worldwide

Nous proposons Dido, un langage dédié (DSL) implicitement parallèle qui capture les spécifications de haut niveau des stencils et génère automatiquement du code parallèle de haute performance pour les architectures à mémoire distribuée. Le code généré utilise ORWL en tant que interface de communication et runtime. Nous montrons que Dido réalise un grand progrès en termes de productivité sans sacrifier les performances. Dido prend en charge une large gamme de calculs stencils ainsi que des applications réelles à base de stencils. Nous montrons que le code généré par Dido est bien structuré et se prête à de différentes optimisations possibles. Nous combinons également la technique de génération de code de Dido avec Pluto l'optimiseur polyédrique de boucles pour améliorer la localité des données. Nous présentons des expériences qui prouvent l'efficacité et la scalabilité du code généré qui atteint de meilleures performances que les implémentations ORWL et MPI écrites à la main
Vérification dynamique formelle de propriétés temporelles sur des applications distribuées réelles by Marion Guthmuller( )

1 edition published in 2015 in French and held by 1 WorldCat member library worldwide

Alors que l'informatique est devenue omniprésente dans notre société actuelle, assurer la qualité d'un logiciel revêt une importance grandissante. Pour accroître cette qualité, l'une des conditions à respecter est la correction du système. Dans cette thèse, nous nous intéressons plus particulièrement aux systèmes distribués mettant en œuvre un ou plusieurs programmes exécutés sur plusieurs machines qui communiquent entre elles à travers le réseau. Dans ce contexte, assurer leur correction est rendu plus difficile par leur hétérogénéité mais également par leurs spécificités communes. Les algorithmes correspondants sont parfois complexes et la prédiction de leur comportement difficilement réalisable sans une étude avancée. Les travaux réalisés au cours de cette thèse mettent en œuvre la vérification dynamique formelle de propriétés temporelles sur des applications distribuées. Cette approche consiste à vérifier l'implémentation réelle d'une application à travers son exécution. L'enjeu majeur est de réussir à appliquer les techniques associées au Model checking dans le cadre d'une vérification sur des implémentations réelles d'applications distribuées et non plus sur des modèles abstraits. Pour cela, nous proposons dans un premier temps une analyse sémantique dynamique par introspection mémoire d'un état système permettant de détecter des états sémantiquement identiques. Puis, nous mettons en œuvre la vérification dynamique formelle de certaines propriétés temporelles : les propriétés de vivacité, formulées à l'aide de la logique LTL_X, et le déterminisme des communications dans les applications MPI. Une évaluation de chacune de ces contributions est réalisée à travers plusieurs expériences
Simulation du mouvement pulmonaire personnalisé par réseau de neurones artificiels pour la radiothérapie externe by Rémy Laurent( )

1 edition published in 2011 in French and held by 1 WorldCat member library worldwide

The development of new techniques in the field of external radiotherapy opens new ways of gaining accuracy in dose distribution, in particular through the knowledge of individual lung motion. The numeric simulation NEMOSIS (Neural Network Motion Simulation System) we describe is based on artificial neural networks (ANN) and allows, in addition to determining motion in a personalized way, to reduce the necessary initial doses to determine it. In the first part, we will present current treatment options, lung motion as well as existing simulation or estimation methods. The second part describes the artificial neural network used and the steps for defining its parameters. An accurate evaluation of our approach was carried out on original patient data. The obtained results are compared with an existing motion estimated method. The extremely short computing time, in the range of milliseconds for the generation of one respiratory phase, would allow its use in clinical routine. Modifications to NEMOSIS in order to meet the requirements for its use in external radiotherapy are described, and a study of the motion of tumor outlines is carried out. This work lays the basis for lung motion simulation with ANNs and validates our approach. Its real time implementation coupled to its predication accuracy makes NEMOSIS promising tool for the simulation of motion synchronized with breathing
Stability of fully asynchronous discrete-time discrete-state dynamic networks by Jacques Mohcine Bahi( )

1 edition published in 2002 in English and held by 1 WorldCat member library worldwide

 
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Parallel iterative algorithms : from sequential to grid computing Parallel iterative algorithms
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Vivier Sylvain Contassot-

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