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Evolutionary algorithms are sophisticated hill-climbers. In this paper, we discuss the ability of this class of local search algorithms to provide useful and efficient heuristics to solve NP-hard problems. Our discussion is illustrated on experiments aiming at solving the job-shop-scheduling problem. We focus on the components of the EA, pointing out the importance of the objective function as well as the manner the operators are applied. Experiments clearly show the efficiency of local search methods in this context, the trade-off between “pure” and hybrid algorithms, as well as the very good performance obtained by simple hill-climbing algorithms. This work has to be regarded as a step towards a better understanding of the way search algorithms wander in a fitness landscape.

In this paper, we present the task allocation tool for the PAROS PARallel Operating System. Such a tool becomes necessary in case of highly parallel systems where load balancing is a key feature for performances enhancement. PAROS tasks allocation tool achieves load balancing through three cooperating components. First, a parallel static allocation algorithm (this is based on an original parallel genetic approach) is used to map parallel programs on available processors of the target architecture. Second, a dynamic allocation algorithm allocates run-time created tasks. Finally, a task migration mechanism is used for fine tuning system load balance situations when mere allocation strategies are not sufficient. Some simulation experiments are presented to evaluate the performances of the proposed allocation tool.

We describe an implementation of a real time path planner for a robot arm with six degrees of freedom moving among dynamical obstacles. The planner is based on a novel technique called the Ariadne's Clew Algorithm. A brief description of this algorithm and parallel implementation of it are presented. Finally we analyze experiments made with this planner.

The goal of the work described in this paper is to build a path planner able to drive a robot in a dynamic environment where the obstacles are moving. In order to do so, we propose a method, called "Ariadne's clew algorithm", to build a global path planner based on the combination of two local planning algorithms: an EXPLORE algorithm and a SEARCH algorithm. The purpose of the EXPLORE algorithm is to collect information about the environment with an increasingly fine resolution by placing landmarks in the searched space. The goal of the SEARCH algorithm is to opportunistically check if the target can be easily reached from any given placed landmark. The Ariadne's clew algorithm is shown to be very fast in most cases allowing planning in dynamic environments. Hence, it is shown to be complete, which means that it is sure to find a path when one exists. Finally, we describe a massively parallel implementation of this algorithm.

International audience

International audience; We propose the first large-scale message passing distributed scheme for parallelizing the computational flow of MOEA/D, a popular decomposition-based evolutionary multi-objective optimization algorithm. We show how synchronicity and workload granularity can impact both quality and computing time, in an extremely fine-grained configuration where each individual in the MOEA/D population is mapped to a single distributed processing unit. More specifically, we deploy our distributed protocol using a large-scale environment of 128 computing cores and conduct a throughout analysis using a broad range of bi-objective combinatorial ρMNK-landscapes. Besides being able to show significant speed-ups while maintaining competitive search quality, our experimental results provide insights into the behavior of the proposed scheme in terms of quality/speed-up trade-offs; thus pushing a step towards the achievement of effective and efficient parallel decomposition-based approaches for large-scale multi-objective optimization.

International audience; In this paper, we address a bi-objective vehicle routing problem in which the total length of routes is minimized as well as the balance of routes, i.e. the difference between the maximal route length and the minimal route length. We propose a meta-heuristic method based on an evolutionary algorithm involving classical multi-objective operators. To improve its efficiency, two mechanisms, which favor the diversification of the search, have been added. First, an elitist diversification mechanism is used in cooperation with classical diversification methodologies. Second, a parallel model designed to take into account the elitist diversification is proposed. Our method is tested on standard benchmarks for the vehicle routing problem. The contribution of the introduced mechanisms is evaluated by different performance metrics. All the experimentations indicate a strict improvement of the generated Pareto set.

International audience; This paper presents ParadisEO-MOEO, a white-box object-oriented generic framework dedicated to the flexible design of evolutionary multi-objective algorithms. This paradigm-free software embeds some features and techniques for Pareto-based resolution and aims to provide a set of classes allowing to ease and speed up the development of computationally efficient programs. It is based on a clear conceptual distinction between the solution methods and the multi-objective problems they are intended to solve. This separation confers a maximum design and code reuse. ParadisEO-MOEO provides a broad range of archive-related features (such as elitism or performance metrics) and the most common Pareto-based fitness assignment strategies (MOGA, NSGA, SPEA, IBEA and more). Furthermore, parallel and distributed models as well as hybridization mechanisms can be applied to an algorithm designed within ParadisEO-MOEO using the whole version of ParadisEO. In addition, GUIMOO, a platform-independant free software dedicated to results analysis for multi-objective problems, is briefly introduced.

We present an ongoing research work on robot motion planning using genetic algorithms. Our goal is to use this technique to build fast motion planners for robot with six or more degree of freedom. After a short review of the existing methods, we will introduce the genetic algorithms by showing how they can be used to solve the invers kinematic problem. In the second part of the paper, we show that the path planning problem can be expressed as an optimization problem and thus solved with a genetic algorithm. We illustrate the approach by building a path planner for a planar arm with two degree of freedom, then we demonstrate the validity of the method by planning paths for an holonomic mobile robot. Finally we describe an implementation of the selected genetic algorithm on a massively parallel machine and show that fast planning response is made possible by using this approach.

This article presents CoBRA, a new parallel coevolutionary algorithm for bi-level optimization. CoBRA is based on a coevolutionary scheme to solve bi-level optimization problems. It handles population-based meta-heuristics on each level, each one cooperating with the other to provide solutions for the overall problem. Moreover, in order to evaluate the relevance of CoBRA against more classical approaches, a new performance assessment methodology, based on rationality, is introduced. An experimental analysis is conducted on a bi-level distribution planning problem, where multiple manufacturing plants deliver items to depots, and where a distribution company controls several depots and distributes items from depots to retailers. The experimental results reveal significant enhancements with respect to a more classical approach, based on a hierarchical scheme.; Cet article présente CoBRA, un nouvel algorithme paralléle et coévolutionnaire pour l'optimisation bi-niveau. CoBRA se base sur un modèle coévolutionnaire pour faire face aux problèmes d'optimisation bi-niveau. Il manipule une méta-heuristique à base de population sur chaque niveau, chacune coopérant avec l'autre de manière à garder une vue générale sur le problème complet. De plus, afin d'étudier la pertinence de CoBRA par rapport aux approches plus classique, une nouvelle méthodologie, basée sur la rationalité est introduite. Est conduite ensuite une étude expérimentale sur un problème bi-niveau de distribution-production, dans lequel des usines contrôlées par une entreprise produisent des marchandises pour des dépôts, et une autre entreprise contrôlant les dépôts se charge de livrer les marchandises à des clients. Cet article se conclut sur l'observation d'un réel gain de performance par rapport à une approche plus classique, basée sur un modèle hiérarchique.

As intrinsic structures, like the number of clusters, is, for real data, a major issue of the clustering problem, we propose, in this paper, CHyGA (Clustering Hybrid Genetic Algorithm) an hybrid genetic algorithm for clustering. CHyGA treats the clustering problem as an optimization problem and searches for an optimal number of clusters characterized by an optimal distribution of instances into the clusters. CHyGA introduces a new representation of solutions and uses dedicated operators, such as one iteration of K-means as a mutation operator. In order to deal with nominal data, we propose a new definition of the cluster center concept and demonstrate its properties. Experimental results on classical benchmarks are given.

International audience; The purpose of the current paper is twofold. First, a unified view of dominance-based multiobjective local search algorithms is proposed. We focus on methods based on the iterative improvement of thenondominated set by means of a neighborhood operator. Next, the effect of current solutions selection and of neighborhood exploration techniques for such purpose is studied. Experiments are conducted on a permutation flowshop scheduling problem in a two- and a three-objective variant.

Within the framework of complex system design, such as aircraft and launch vehicles, the presence of computationallyintensive objective and/or constraint functions (e.g., finite element models and multidisciplinary analyses)coupled with the dependence on discrete and unordered technological design choices results in challenging optimizationproblems. Furthermore, part of these technological choices is associated to a number of specific continuous anddiscrete design variables which must be taken into consideration only if specific technological and/or architecturalchoices are made. As a result, the optimization problem which must be solved in order to determine the optimalsystem design presents a dynamically varying search space and feasibility domain.The few existing algorithms which allow solving this particular type of problems tend to require a large amountof function evaluations in order to converge to the feasible optimum, and result therefore inadequate when dealingwith the computationally intensive problems which can often be encountered within the design of complex systems.For this reason, this thesis explores the possibility of performing constrained mixed-variable and variable-size designspace optimization by relying on surrogate model-based design optimization performed with the help of Gaussianprocesses, also known as Bayesian optimization. More specifically, 3 main axes are discussed. First, the Gaussianprocess surrogate modeling of mixed continuous/discrete functions and the associated challenges are extensivelydiscussed. A unifying formalism is proposed in order to facilitate the description and comparison between theexisting kernels allowing to adapt Gaussian processes to the presence of discrete unordered variables. Furthermore,the actual modeling performances of these various kernels are tested and compared on a set of analytical and designrelated benchmarks with different characteristics and parameterizations.In the second part of the thesis, the possibility of extending the mixed continuous/discrete surrogate modeling toa context of Bayesian optimization is discussed. The theoretical feasibility of said extension in terms of objective/-constraint function modeling as well as acquisition function definition and optimization is shown. Different possiblealternatives are considered and described. Finally, the performance of the proposed optimization algorithm, withvarious kernels parameterizations and different initializations, is tested on a number of analytical and design relatedtest-cases and compared to reference algorithms.In the last part of this manuscript, two alternative ways of adapting the previously discussed mixed continuous/discrete Bayesian optimization algorithms in order to solve variable-size design space problems (i.e., problemscharacterized by a dynamically varying design space) are proposed. The first adaptation is based on the paralleloptimization of several sub-problems coupled with a computational budget allocation based on the informationprovided by the surrogate models. The second adaptation, instead, is based on the definition of a kernel allowingto compute the covariance between samples belonging to partially different search spaces based on the hierarchicalgrouping of design variables. Finally, the two alternatives are tested and compared on a set of analytical and designrelated benchmarks.Overall, it is shown that the proposed optimization methods allow to converge to the various constrained problemoptimum neighborhoods considerably faster when compared to the reference methods, thus representing apromising tool for the design of complex systems.; Dans le cadre de la conception de systèmes complexes, tels que les aéronefs et les lanceurs, la présence de fonctions d'objectifs et/ou de contraintes à forte intensité de calcul (e.g., modèles d'éléments finis) couplée à la dépendance de choix de conception technologique discrets et non ordonnés entraîne des problèmes d'optimisation difficiles. De plus, une partie de ces choix technologiques est associée à un certain nombre de variables de conception continues et discrètes spécifiques qui ne doivent être prises en considération que si des choix technologiques spécifiques sont faits. Par conséquent, le problème d'optimisation qui doit être résolu afin de déterminer la conception optimale du système présente un espace de recherche et un domaine de faisabilité variant de façon dynamique. Les algorithmes existants qui permettent de résoudre ce type particulier de problèmes ont tendance à exiger une grande quantité d'évaluations de fonctions afin de converger vers l'optimum réalisable, et sont donc inadéquats lorsqu'il s'agit de résoudre les problèmes à forte intensité de calcul. Pour cette raison, cette thèse explore la possibilité d'effectuer une optimisation de l'espace de conception contraint à variables mixtes et de taille variable en s'appuyant sur des méthodes d’optimisation à base de modèles de substitution créés à l'aide de processus Gaussiens, également connue sous le nom d'optimisation Bayésienne. Plus spécifiquement, 3 axes principaux sont discutés. Premièrement, la modélisation de substitution par processus gaussien de fonctions mixtes continues/discrètes et les défis qui y sont associés sont discutés en détail. Un formalisme unificateur est proposé afin de faciliter la description et la comparaison entre les noyaux existants permettant d'adapter les processus gaussiens à la présence de variables discrètes non ordonnées. De plus, les performances réelles de modélisation de ces différents noyaux sont testées et comparées sur un ensemble de benchmarks analytiques et de conception ayant des caractéristiques et des paramétrages différents. Dans la deuxième partie de la thèse, la possibilité d'étendre la modélisation de substitution mixte continue/discrète à un contexte d'optimisation Bayésienne est discutée. La faisabilité théorique de cette extension en termes de modélisation de la fonction objectif/contrainte ainsi que de définition et d'optimisation de la fonction d'acquisition est démontrée. Différentes alternatives possibles sont considérées et décrites. Enfin, la performance de l'algorithme d'optimisation proposé, avec diverses paramétrisations des noyaux et différentes initialisations, est testée sur un certain nombre de cas-test analytiques et de conception et est comparée aux algorithmes de référence.Dans la dernière partie de ce manuscrit, deux approches permettant d'adapter les algorithmes d'optimisation bayésienne mixte continue/discrète discutés précédemment afin de résoudre des problèmes caractérisés par un espace de conception variant dynamiquement au cours de l’optimisation sont proposées. La première adaptation est basée sur l'optimisation parallèle de plusieurs sous-problèmes couplée à une allocation de budget de calcul basée sur l'information fournie par les modèles de substitution. La seconde adaptation, au contraire, est basée sur la définition d'un noyau permettant de calculer la covariance entre des échantillons appartenant à des espaces de recherche partiellement différents en fonction du regroupement hiérarchique des variables dimensionnelles. Enfin, les deux alternatives sont testées et comparées sur un ensemble de cas-test analytiques et de conception.Globalement, il est démontré que les méthodes d'optimisation proposées permettent de converger vers les optimums des différents types de problèmes considérablement plus rapidement par rapport aux méthodes existantes. Elles représentent donc un outil prometteur pour la conception de systèmes complexes.

International audience

International audience

International audience; To sustain the rapidly increasing air traffic demand, the future air traffic management system will rely on a concept, called Trajectory-Based Operations (TBO), that will require aircraft to follow an assigned 4D trajectory (time-constrained trajectory) with high precision. TBO involves separating aircraft via strategic (long-term) trajectory deconfliction rather than the currently-practicing tactical (short-term) conflict resolution. In this context, this chapter presents a strategic trajectory planning approach aiming at minimizing the number of conflicts between aircraft trajectories for a given day. The proposed methodology allocates an alternative departure time, a horizontal flight path, and a flight level to each aircraft at a nation-wide scale.In real-life situations, aircraft may arrive at a given position with some uncertainties on its curvilinear abscissa due to external events. To ensure robustness of the strategic trajectory plan, the aircraft arrival time to any given position will be represented here by a probabilistic distribution over its nominal assigned arrival time.The proposed approach optimizes the 4D trajectory of each aircraft so as to minimize the probability of potential conflicts between trajectories. A hybrid-metaheuristic optimization algorithm has been developed to solve this large-scale mixed-variable optimization problem. The algorithm is implemented and tested with real air traffic data taking into account uncertainty over the French airspace for which a conflict-free and robust 4D trajectory plan is produced.

International audience; Algorithm portfolios are known to offer robust performances, efficiently overcoming the weakness of every single algorithm on some particular problem instances. Two complementary approaches to get the best out of an algorithm portfolio is to achieve algorithm selection (AS), and to define a scheduler, sequentially launching a few algorithms on a limited computational budget each. The presented Algorithm Selector And Prescheduler system relies on the joint optimization of a pre-scheduler and a per instance AS, selecting an algorithm well-suited to the problem instance at hand. ASAP has been thoroughly evaluated against the state-of-the-art during the ICON challenge for algorithm selection, receiving an honourable mention. Its evaluation on several combinatorial optimization benchmarks exposes surprisingly good results of the simple heuristics used; some extensions thereof are presented and discussed in the paper.

International audience; The aim of this chapter is to scrutinize problems, modelling approaches and algorithms employed to adapt and parameterize the Material Requirement Planning (MRP) method under lead time uncertainty and to discourse about some potential research areas. The analysis and discussion could help the community deal with variabilities, formalizing the uncertainty of lead times and facilitating development of methods for solving identified problems.

Cloud computing has emerged during the last decade to be widely adopted nowadays in several IT areas. It consists to propose market or not marketoriented resources as services that can be consumed in a ubiquitous, flexible and transparent way. In this PhD thesis, we deal with scheduling, one of the major cloud computing issue. According to the targeted cloud configuration, we have identified three levels of scheduling: service-level, task-level and Virtual Machine-level. We revisit the problem modeling, the design and the implementation of multi-objective metaheuristics for each scheduling level of the cloud. The proposed metaheuristicsbased schedulers address different criteria including energy consumption, greenhouse gas emissions, profit and QoS (cost and response time). We prove their adaptability to the cloud constraints by integrating them as a part of the OpenNebula cloud manager. Moreover, our schedulers have been extensively experimented using realistic cloud configurations on Grid'5000, considered as an infrastructure as a service (IAAS), and concrete scenarios based on Amazon EC2 instances and prices. The reported results show that our proposed methods outperform existing scheduling approaches in terms of all previously cited criteria.; Le cloud computing a émergé au cours de la dernière décennie pour être largement adopté aujourd'hui dans plusieurs domaines de l'informatique. Il consiste à proposer des ressources axées, ou non, sur le marché sous forme de services qui peuvent être consommés de manière souple et transparente. Dans cette thèse, nous traitons le problème d'ordonnancement, un des enjeux majeurs du cloud. Selon la configuration de cloud ciblée, nous avons identifié trois niveaux d'ordonnancement : niveau service, niveau tâche et niveau machine virtuelle. Nous revisitons la modélisation du problème, la conception et l'implémentation des métaheuristiques multiobjectives pour chaque niveau d'ordonnancement du cloud. Les ordonnanceurs à base de métaheuristiques que nous proposons portent sur différents critères notamment la consommation d'énergie, les émissions de gaz à effet de serre, le profit et la qualité du service (coût et temps de réponse). Nous prouvons leur capacité d'adaptation aux contraintes du cloud en les intégrant au sein du gestionnaire de cloud OpenNebula. De plus, nos ordonnanceurs ont été largement expérimentés utilisant des configurations réalistes de cloud sur Grid'5000, en tant qu'infrastructure en tant que service (IAAS), et des scénarios concrets basés sur les instances et les tarifications d'Amazon EC2. Les résultats présentés montrent que les méthodes que nous proposons surpassent les approches l'ordonnancement existantes sur tous les critères cités précédemment.

Cloud computing has emerged during the last decade to be widely adopted nowadays in several IT areas. It consists to propose market or not marketoriented resources as services that can be consumed in a ubiquitous, flexible and transparent way. In this PhD thesis, we deal with scheduling, one of the major cloud computing issue. According to the targeted cloud configuration, we have identified three levels of scheduling: service-level, task-level and Virtual Machine-level. We revisit the problem modeling, the design and the implementation of multi-objective metaheuristics for each scheduling level of the cloud. The proposed metaheuristicsbased schedulers address different criteria including energy consumption, greenhouse gas emissions, profit and QoS (cost and response time). We prove their adaptability to the cloud constraints by integrating them as a part of the OpenNebula cloud manager. Moreover, our schedulers have been extensively experimented using realistic cloud configurations on Grid'5000, considered as an infrastructure as a service (IAAS), and concrete scenarios based on Amazon EC2 instances and prices. The reported results show that our proposed methods outperform existing scheduling approaches in terms of all previously cited criteria.; Le cloud computing a émergé au cours de la dernière décennie pour être largement adopté aujourd'hui dans plusieurs domaines de l'informatique. Il consiste à proposer des ressources axées, ou non, sur le marché sous forme de services qui peuvent être consommés de manière souple et transparente. Dans cette thèse, nous traitons le problème d'ordonnancement, un des enjeux majeurs du cloud. Selon la configuration de cloud ciblée, nous avons identifié trois niveaux d'ordonnancement : niveau service, niveau tâche et niveau machine virtuelle. Nous revisitons la modélisation du problème, la conception et l'implémentation des métaheuristiques multiobjectives pour chaque niveau d'ordonnancement du cloud. Les ordonnanceurs à base de métaheuristiques que nous proposons portent sur différents critères notamment la consommation d'énergie, les émissions de gaz à effet de serre, le profit et la qualité du service (coût et temps de réponse). Nous prouvons leur capacité d'adaptation aux contraintes du cloud en les intégrant au sein du gestionnaire de cloud OpenNebula. De plus, nos ordonnanceurs ont été largement expérimentés utilisant des configurations réalistes de cloud sur Grid'5000, en tant qu'infrastructure en tant que service (IAAS), et des scénarios concrets basés sur les instances et les tarifications d'Amazon EC2. Les résultats présentés montrent que les méthodes que nous proposons surpassent les approches l'ordonnancement existantes sur tous les critères cités précédemment.

Solving efficiently large benchmarks of NP-hard permutation-based problems requires the development of hybrid methods combining different classes of optimization methods. Indeed, it is now acknowledged that such methods perform better than traditional optimization methods when used separately. The key challenge is how to find connections between the divergent search strategies used in each class of methods in order to build efficient hybridization strategies. Genetic algorithms (GAs) are very popular population-based metaheuristics based on stochastic evolutionary operators. The hybridization of GAs with tree-based exact methods such as Branch-and-Bound is a promising research trend. B&B algorithms are based on an implicit enumeration of the solution space represented as a tree. Our hybridization approach consists in providing a common solution and search space coding and associated search operators enabling an efficient cooperation between the two methods. The tree-based representation of the solution space is traditionally used in B&B algorithms to enumerate the solutions of the problem at hand. In this thesis, this special representation is adapted to metaheuristics. The encoding of permutations as natural numbers, which refer to their lexicographic enumeration in the tree, is proposed as a new way to represent the solution space of permutation problems in metaheuristics. This encoding approach is based on the mathematical properties of permutations (Lehmer codes, inversion tables, etc.). Mapping functions between the two representations (permutations and numbers) and special search operators adapted to the encoding are defined for general permutation problems, with respect to the theory of representation. This common representation allows the design of efficient cooperation strategies between GAs and B&B algorithms. In this thesis, two hybridization schemes combining GAs with B&B based on this common representation are proposed. The two hybridization approaches HGABB/HAGABB (Hybrid Adaptive GA-B&B) and COBBIGA (cooperative B&B interval-based GA), have been validated on standard benchmarks of one of the hardest permutation-based problems, the three dimensional quadratic assignment problem (Q3AP). In order to solve large benchmarks of permutationbased problems, a parallelization for computational grids is also proposed for the two hybrid schemes. This parallelization is based on space decomposition techniques (the decomposition by intervals) used in parallel B&B algorithms. From the implementation point of view, in order to facilitate further design and implementation of hybrid methods combining metaheuristics with tree-based exact methods, a hybridization C++ framework integrated to the framework for metaheuristics ParadisEO is developed. The new framework is used to conduct extensive experiments over the computational grid Grid'5000.; La résolution efficace de problèmes d'optimisation a permutation de grande taille nécessite le développement de méthodes hybrides complexes combinant différentes classes d'algorithmes d'optimisation. L'hybridation des metaheuristiques avec les méthodes exactes arborescentes, tel que l'algorithme du branch-and-bound (B&B), engendre une nouvelle classe d'algorithmes plus efficace que ces deux classes de méthodes utilisées séparément. Le défi principal dans le développement de telles méthodes consiste a trouver des liens ou connections entre les stratégies de recherches divergentes utilisées dans les deux classes de méthodes. Les Algorithmes Genetiques (AGs) sont des metaheuristiques, a base de population, tr'es populaires bas'es sur des op'erateurs stochastiques inspirés de la théorie de l'évolution. Contrairement aux AGs et aux m'etaheuristiques généralement, les algorithmes de B&B sont basées sur l'énumération implicite de l'espace de recherche représente par le moyen d'un arbre, dit arbre de recherche. Notre approche d'hybridation consiste a définir un codage commun des solutions et de l'espace de recherche ainsi que des opérateurs de recherche ad'equats afin de permettre un couplage efficace de bas niveau entre les deux classes de méthodes AGs et B&B. La représentation de l'espace de recherche par le moyen d'arbres est traditionnellement utilis'ee dans les algorithmes de B&B. Dans cette thèse, cette représentation a été adaptée aux metaheuristiques. L'encodage des permutations au moyen de nombres naturels faisant référence a l'ordre d'énumération lexicographique des permutations dans l'arbre du B&B, est proposé comme une nouvelle manière de représenter l'espace de recherche des problèmes 'a permutations dans les metaheuristiques. Cette méthode de codage est basée sur les propriétés mathématiques des permutations, 'a savoir les codes de Lehmer et les tables d'inversions ainsi que les système d'énumération factoriels. Des fonctions de transformation permettant le passage entre les deux représentations (permutations et nombres) ainsi que des opérateurs de recherche adaptes au codage, sont définis pour les problèmes 'a permutations généralisés. Cette représentation, désormais commune aux metaheuristiques et aux algorithmes de B&B, nous a permis de concevoir des stratégies d'hybridation et de collaboration efficaces entre les AGs et le B&B. En effet, deux approches d'hybridation entre les AGs et les algorithmes de B&B (HGABB et COBBIGA) bas'es sur cette représentation commune ont été proposées dans cette thèse. Pour validation, une implémentation a été réalisée pour le problème d'affectation quadratique 'a trois dimension (Q3AP). Afin de résoudre de larges instances de ce problème, nous avons aussi propose une parallélisation pour les deux algorithme hybrides, basée sur des techniques de décomposition d'espace (décomposition par intervalle) utilisées auparavant pour la parallélisation des algorithmes de B&B. Du point de vue implémentation, afin de faciliter de futurs conceptions et implémentations de méthodes hybrides combinant metaheuristiques et méthodes exacte arborescentes, nous avons développe une plateforme d'hybridation intégrée au logiciel pour metaheuristiques, ParadisEO. La nouvelle plateforme a été utilisée pour réaliser des expérimentations intensives sur la grille de calcul Grid'5000.

International audience

International audience

Many real-world optimization problems, especially in the field of logistics, have to face a lot of difficulties. Indeed, they are often characterized by large and complex search spaces, multiple conflicting objective functions, and a host of uncertainties that have to be taken into account. Metaheuristics are natural candidates to solve those problems and make them preferable to classical optimization methods. However, the development of efficient metaheuristics results in a complex engineering process. The core subject of this work lies in the design, implementation and experimental analysis of metaheuristics for multiobjective optimization, together with their applications to logistic problems from routing and scheduling. Firstly, a unified view of such approaches is presented and then integrated into a software framework for their implementation, ParadisEO-MOEO. Next, some cooperative approaches combining metaheuristics for multiobjective optimization are proposed. At last, the issue of uncertainty handling is discussed in the context of multiobjective optimization.; De nombreux problèmes d'optimisation issus du monde réel, notamment dans le domaine de la logistique, doivent faire face à beaucoup de difficultés. En effet, ils sont souvent caractérisés par des espaces de recherche vastes et complexes, de multiples fonctions objectif contradictoires, et une foule d'incertitudes qui doivent être prises en compte. Les métaheuristiques sont des candidates naturelles pour résoudre ces problèmes, ce qui les rend préférables aux méthodes d'optimisation classiques. Toutefois, le développement de métaheuristiques efficaces découle d'un processus de recherche complexe. Le cœur de ce travail réside en la conception, l'implémentation et l'analyse expérimentale de métaheuristiques pour l'optimisation multiobjectif, ainsi que leurs applications à des problèmes logistiques de tournées et d'ordonnancement. Tout d'abord, une vue unifiée de ces approches est présentée, puis intégrée dans une plateforme logicielle dédiée à leur implémentation, ParadisEO-MOEO. Ensuite, plusieurs approches de coopération, combinant des métaheuristiques pour l'optimisation multiobjectif, sont proposées. Enfin, la question de la prise en compte l'incertitude est abordée dans le contexte de l'optimisation multiobjectif.