Explanation-Based Large Neighborhood Search

International audienceOne of the most well-known and widely used local search techniques for solving optimization problems in Constraint Programming is the Large Neigh-borhood Search (LNS) algorithm. Such a technique is, by nature, very flexible and can be easily integrated within standard backtracking procedures. One of its drawbacks is that the relaxation process is quite often problem dependent. Several works have been dedicated to overcome this issue through problem independent parameters. Nevertheless, such generic approaches need to be carefully parameter-ized at the instance level. In this paper, we demonstrate that the issue of finding a problem independent neighborhood generation technique for LNS can be addressed using explanation-based neighborhoods. An explanation is a subset of constraints and decisions which justifies a solver event such as a domain modification or a conflict. We evaluate our proposal for a set of optimization problems. We show that our approach is at least competitive with or even better than state-of-the-art algorithms and can be easily combined with state-of-the-art neighborhoods. Such results pave the way to a new use of explanation-based approaches for improving search

Combining finite and continuous solvers Towards a simpler solver maintenance

International audienceCombining efficiency with reliability within CP systems is one of the main concerns of CP developers. This paper presents a simple and efficient way to connect Choco and Ibex, two CP solvers respectively specialised on finite and continuous domains. This enables to take advantage of the most recent advances of the continuous community within Choco while saving development and maintenance resources, hence ensuring a better software quality

Prototyper des Moteurs de Propagation avec un DSL

National audienceConstraint propagation is at the heart of constraint solvers. Two main trends co-exist: variable-oriented propagation engines and constraint-oriented propagation engines. Those two approaches ensure the same consistency level, generally arc-consistency, but their efficiency (computation time) can be quite different depending on the instance solved. It is usually accepted that there is no best approach in general, and modern constraint solvers implement only one. In this paper, we would like to go a step further providing a solver independent language at the modeling stage to enable the design of propagation engine prototypes. We validate our proposal with a reference implementation based on Choco and the MiniZinc modeling language

Fiabilité et maintenabilité du groupe motopropulseur d'autobus urbains

Fiabilité du groupe selon sa capacité à remplir une mission -- Programme de maintenance de la STCUM -- Banque de données de la STCUM -- Description de la flotte d'autobus de la STCUM -- Composantes suivies via la banque de données -- Durée de vie d'une composante -- Objectif : optimisation de la maintenance préventive -- Description du groupe motopropulseur -- Moteurs -- Accessoires -- Théories relatives à l'analyse de fiabilité -- Tests de valeurs extrêmes -- Modèles de fiabilité -- Lois de probabilité utilisées en fiabilité -- Méthodes d'estimation des paramètres -- Test de validation des modèles -- Analyse des modèles générés -- Méthode de filtrage des données -- Élaboration des modèles pour chaque unité -- Logiciel d'analyse RELCODE -- Tableaux d'analyse -- Optimisation des périodes de maintenance -- Optimisation de la maintenance basée sur les coûts d'exploitation -- Optimisation des périodes de maintenance basée sur la fiabilité -- Obtention des coûts du correctif, préventif et de la main d'oeuvre -- Utilisation du logiciel RELCODE pour l'optimisation

Contrôle de la propagation et de la recherche dans un solveur de contraintes

La programmation par contraintes est souvent décrite, utopiquement, comme un paradigme déclaratif dans lequel l utilisateur décrit son problème et le solveur le résout. Bien entendu, la réalité des solveurs de contraintes est plus complexe, et les besoins de personnalisation des techniques de modélisation et de résolution évoluent avec le degré d expertise des utilisateurs. Cette thèse porte sur l enrichissement de l arsenal des techniques disponibles dans les solveurs de contraintes. D une part, nous étudions la contribution d un système d explications à l exploration de l espace de recherche, dans le cadre spécifique d une recherche locale. Deux heuristiques de voisinages génériques exploitant singulièrement les explications sont décrites. La première se base sur la difficulté de réparer une solution partiellement détruite, la seconde repose sur la nature non-optimale de la solution courante. Ces heuristiques mettent à jour la structure interne des problèmes traités pour construire des voisins de bonne qualité pour une recherche à voisinage large. Elles sont complémentaires d autres heuristiques de voisinages génériques, avec lesquels elles peuvent être combinées efficacement. De plus, nous proposons de rendre le système d explications paresseux afin d en minimiser l empreinte. D autre part, nous effectuons un état des lieux des savoir-faire relatifs aux moteurs de propagation pour les solveurs de contraintes. Ces données sont exploitées opérationnellement à travers un langage dédié qui permet de personnaliser la propagation au sein d un solveur, en fournissant des structures d implémentation et en définissant des points de contrôle dans le solveur. Ce langage offre des concepts de haut niveau permettant à l utilisateur d ignorer les détails de mise en œuvre du solveur, tout en conservant un bon niveau de flexibilité et certaines garanties. Il permet l expression de schémas de propagation spécifiques à la structure interne de chaque problème. La mise en œuvre et les expérimentations ont été effectués dans le solveur de contraintes Choco. Cette thèse a donné lieu à une nouvelle version de l outil globalement plus efficace et nativement expliqué.Constraint programming is often described, idealistically, as a declarative paradigm in which the user describes the problem and the solver solves it. Obviously, the reality of constraint solvers is more complex, and the needs in customization of modeling and solving techniques change with the level of expertise of users. This thesis focuses on enriching the arsenal of available techniques in constraint solvers. On the one hand, we study the contribution of an explanation system to the exploration of the search space in the specific context of a local search. Two generic neighborhood heuristics which exploit explanations singularly are described. The first one is based on the difficulty of repairing a partially destroyed solution, the second one is based on the non-optimal nature of the current solution. These heuristics discover the internal structure of the problems to build good neighbors for large neighborhood search. They are complementary to other generic neighborhood heuristics, with which they can be combined effectively. In addition, we propose to make the explanation system lazy in order to minimize its footprint. On the other hand, we undertake an inventory of know-how relative to propagation engines of constraint solvers. These data are used operationally through a domain specific language that allows users to customize the propagation schema, providing implementation structures and defining check points within the solver. This language offershigh-level concepts that allow the user to ignore the implementation details, while maintaining a good level of flexibility and some guarantees. It allows the expression of propagation schemas specific to the internal structure of each problem solved. Implementation and experiments were carried out in the Choco constraint solver, developed in this thesis. This has resulted in a new version of the overall effectiveness and natively explained tool.NANTES-ENS Mines (441092314) / SudocSudocFranceF

Combining finite and continuous solvers Towards a simpler solver maintenance

International audienceCombining efficiency with reliability within CP systems is one of the main concerns of CP developers. This paper presents a simple and efficient way to connect Choco and Ibex, two CP solvers respectively specialised on finite and continuous domains. This enables to take advantage of the most recent advances of the continuous community within Choco while saving development and maintenance resources, hence ensuring a better software quality

Prototyper des Moteurs de Propagation avec un DSL

National audienceConstraint propagation is at the heart of constraint solvers. Two main trends co-exist: variable-oriented propagation engines and constraint-oriented propagation engines. Those two approaches ensure the same consistency level, generally arc-consistency, but their efficiency (computation time) can be quite different depending on the instance solved. It is usually accepted that there is no best approach in general, and modern constraint solvers implement only one. In this paper, we would like to go a step further providing a solver independent language at the modeling stage to enable the design of propagation engine prototypes. We validate our proposal with a reference implementation based on Choco and the MiniZinc modeling language

Effect of apoC-III gene polymorphisms on the lipoprotein-lipid profile of viscerally obese men

Abdominal visceral adipose tissue (AT) accumulation is associated with an atherogenic metabolic profile that includes increased plasma triglyceride (TG), low HDL cholesterol levels, and an insulin-resistant hyperinsulinemic state. Whereas the apolipoprotein (apo) C-III C3238G gene variant, often referred to as the SstI polymorphism, has been related to variations in plasma TG concentrations, another variation within the insulin responsive element (C-482T) of the apoC-III gene has been associated with greater glucose and insulin responses to an oral glucose tolerance test (OGTT); however, these results were obtained in nonobese individuals. We therefore investigated the effects of three apoC-III gene polymorphisms, namely SstI, C-482T, and T-455C, on fasting plasma lipoprotein-lipid levels and response to a 75 g OGTT in a sample of 122 viscerally obese men (abdominal visceral AT area ⩾130 cm2). Among the three gene variants that were examined, the SstI variation was the only one found to be associated with hypertriglyceridemia. Indeed, S1/S2 heterozygotes (n = 24) were characterized by increased fasting plasma TG concentrations compared with S1/S1 homozygotes (n = 98) (mean ± SD: 3.03 ± 1.58 vs. 2.34 ± 0.95 mmol/l respectively, P < 0.05). The higher TG concentrations in S1/S2 were associated with the presence of smaller, denser LDL particles compared with S1/S1 subjects (LDL peak particle diameter: 24.8 ± 0.5 nm vs. 25.1 ± 0.5 nm respectively, P < 0.05). Furthermore, there was no association between the response to the OGTT and any of the apoC-III gene variants (SstI, T-455C, or C-482T) examined

A Framework for Edge Infrastructures Monitoring

By relying on small sized and massively distributed infrastructures, the Edge computingparadigm aims at supporting the low latency and high bandwidth requirements of the next generationservices that will leverage IoT devices (e.g., video cameras, sensors). To favor the advent of this paradigm,management services, similar to the ones that made the success of Cloud computing platforms, should beproposed. However, they should be designed in order to cope with the limited capabilities of the resourcesthat are located at the edge. In that sense, they should mitigate as much as possible their footprint. Amongthe different management services that need to be revisited, we investigate in this paper the monitoring one.Monitoring functions tend to become compute-, storage- and network-intensive, in particular because theywill be used by a large part of applications that rely on real-time data. To reduce as much as possible thefootprint of the whole monitoring service, we propose to mutualize identical processing functions amongdifferent tenants while ensuring their quality-of-service (QoS) expectations.We formalize our approach asa constraint satisfaction problem and show through micro-benchmarks its relevance to mitigate computeand network footprints.En s’appuyant sur des infrastructures de petite taille et massivement distribuées, le EdgeComputing cherche à répondre aux besoins en faible latence et grande bande passante des applicationsde nouvelle génération qui favorisent l’utilisation de l’Internet des objets (par exemple, les camérasvidéo, les capteurs). Pour mettre en œuvre ce paradigme, des services de gestion, similaires à ceuxqui ont permis le succès des plates-formes du Cloud Computing, doivent être proposés. Cependant, ilsdoivent être conçus de manière à faire face aux capacités limitées des ressources situées à la périphériedu réseau. Autrement dit, ils doivent réduire autant que possible leur empreinte. Parmi les différentsservices de gestion qui doivent être revisités, nous étudions dans cet article le service de supervision.Les fonctions de supervision ont tendance à nécessiter de grandes capacités de calcul, de stockage et deréseau parce qu’elles sont utilisées par une grande partie d’applications qui nécessite une supervisionen temps réel. Afin de réduire au maximum l’empreinte du service de supervision, nous proposonsde mutualiser des fonctions de traitement identiques entre différents tenants tout en garantissant leursattentes en qualité de service (QoS). Nous formalisons notre approche en tant qu’un problème desatisfaction de contraintes et montrons à l’aide de micro-test sa pertinence pour atténuer l’empreintede calcul et réseau