Distribution et synchronisation des simulations de Systèmes Multi-Agents

Multi-Agent Systems (MAS) simulation allows to explain and predict the behavior of complex systems in various fields such as epidemiology, economy or environment. The large size of studied models leads to the usage of High Performance Computing and distributed simulation to overcome those limits. The naturally parallel aspect of agents make them excellent candidates to the distributed execution, that however poses many problems, such as data continuity, load balancing or data synchronisation between processes. A generic software architecture that allows to solve those problems in a flexible way and independently from the development context is proposed. An interface based design brings out independent and abstract components required for the distribution of any MAS simulation. We propose a qualitative and quantitative analysis of load balancing methods on the one hand, notably based on the application of graph partitioning to the distributed simulation of MAS, and of data synchronisation modes on the other hand, among which some allow the management of concurrent reads and writes between processes. This analysis shows that advantages of each method depend on models or user needs, hence the interest for the design of modular simulation platforms based on interfaces that allow to easily integrate new methods. The proposed software architecture essentially comes from our development experience of FPMAS, a C++ distributed MAS simulation platform based on proposed solutions.La simulation de Systèmes Multi-Agents (SMA) permet d’expliquer et de prédire le comportement des systèmes complexes dans de nombreux domaines tels que l’épidémiologie, l’économie ou l’environnement. La grande taille des modèles étudiés mène à l’utilisation du Calcul Haute Performance et de la simulation distribuée pour lever ces limites. L’aspect naturellement parallèle des agents en fait d’excellents candidats à l’exécution distribuée, qui pose cependant de nombreux problèmes, comme la continuité des données, l’équilibrage de charge ou la synchronisation des données entre les processus. Une architecture logicielle générique permettant de résoudre ces problèmes de manière flexible et indépendamment du contexte de développement est proposée. Une conception par interface fait émerger des composants indépendants et abstraits nécessaires à la distribution de toute simulation de SMA. Nous proposons une analyse qualitative et quantitative de méthodes d’équilibrage de charge d’une part, notamment basées sur l’application de partitionnements de graphe à la simulation distribuée de SMA, et de modes de synchronisation des données d’autre part, dont certains permettent la gestion des lectures et écritures concurrentes entre les processus. Cette analyse montre que les avantages de chaque méthode dépendent des modèles et des besoins des utilisateurs, d’où l’intérêt de la conception de plateformes de simulation modulables basées sur des interfaces permettant de facilement intégrer de nouvelles méthodes. L’architecture logicielle proposée est essentiellement issue de notre expérience de développement de FPMAS, une plateforme C++ de simulation distribuée de SMA basée sur les solutions proposées

Distribution et synchronisation des simulations de Systèmes Multi-Agents

Multi-Agent Systems (MAS) simulation allows to explain and predict the behavior of complex systems in various fields such as epidemiology, economy or environment. The large size of studied models leads to the usage of High Performance Computing and distributed simulation to overcome those limits. The naturally parallel aspect of agents make them excellent candidates to the distributed execution, that however poses many problems, such as data continuity, load balancing or data synchronisation between processes. A generic software architecture that allows to solve those problems in a flexible way and independently from the development context is proposed. An interface based design brings out independent and abstract components required for the distribution of any MAS simulation. We propose a qualitative and quantitative analysis of load balancing methods on the one hand, notably based on the application of graph partitioning to the distributed simulation of MAS, and of data synchronisation modes on the other hand, among which some allow the management of concurrent reads and writes between processes. This analysis shows that advantages of each method depend on models or user needs, hence the interest for the design of modular simulation platforms based on interfaces that allow to easily integrate new methods. The proposed software architecture essentially comes from our development experience of FPMAS, a C++ distributed MAS simulation platform based on proposed solutions.La simulation de Systèmes Multi-Agents (SMA) permet d’expliquer et de prédire le comportement des systèmes complexes dans de nombreux domaines tels que l’épidémiologie, l’économie ou l’environnement. La grande taille des modèles étudiés mène à l’utilisation du Calcul Haute Performance et de la simulation distribuée pour lever ces limites. L’aspect naturellement parallèle des agents en fait d’excellents candidats à l’exécution distribuée, qui pose cependant de nombreux problèmes, comme la continuité des données, l’équilibrage de charge ou la synchronisation des données entre les processus. Une architecture logicielle générique permettant de résoudre ces problèmes de manière flexible et indépendamment du contexte de développement est proposée. Une conception par interface fait émerger des composants indépendants et abstraits nécessaires à la distribution de toute simulation de SMA. Nous proposons une analyse qualitative et quantitative de méthodes d’équilibrage de charge d’une part, notamment basées sur l’application de partitionnements de graphe à la simulation distribuée de SMA, et de modes de synchronisation des données d’autre part, dont certains permettent la gestion des lectures et écritures concurrentes entre les processus. Cette analyse montre que les avantages de chaque méthode dépendent des modèles et des besoins des utilisateurs, d’où l’intérêt de la conception de plateformes de simulation modulables basées sur des interfaces permettant de facilement intégrer de nouvelles méthodes. L’architecture logicielle proposée est essentiellement issue de notre expérience de développement de FPMAS, une plateforme C++ de simulation distribuée de SMA basée sur les solutions proposées

A Synchronized and Dynamic Distributed Graph structure to allow the native distribution of Multi-Agent System simulations

International audienceMulti-Agent Systems (MAS) are naturally good candidates for large-scale parallel simulations. However, implementing MAS simulations for distributed memory architectures, such as High Performance Computing clusters, is still complex for non-experts. In this article we present the principle of a Dynamic Distributed Graph structure, that enables the native distribution of MAS simulations. Most of the distribution related issues such as dynamic load-balancing, time synchronization and data migration across processes can be completely automated and abstracted for the user, who can safely design distribution independent MAS models. The major interest of our contribution is the transparent management of concurrent read / write requests across distant processes, a significant feature not provided by surveyed platforms. We also present FPMAS, an open source C++ implementation of a Distributed Multi-Agent System Simulation platform based on the Distributed Graph structure

Politiques de synchronisation dans les systèmes multi-agents distribués parallèles

National audienceParmi les méthodes de modélisation/simulation, les systèmes multi-agents présentent un intérêt particulier pour simuler les systèmes complexes. Lorsque la taille des modèles croît, le recours aux systèmes multi-agents parallèles est nécessaire mais pose de nombreux problèmes. Dans cet article, nous nous intéressons à l'impact de la synchronisation sur la définition des modèles et leur exécution. Nous mettons en évidence des problématiques de synchronisation à travers des instances de modèles puis nous analysons expérimentalement l'impact des politiques de synchronisation sur des exécutions de grande taille

Politiques de synchronisation dans les systèmes multi-agents distribués parallèles

Among simulation or modelisation methods, multi-agent systems are an interesting candidate to simulate complex systems. As the size of the model's increases, the use of parallel multi-agent systems is mandatory but comes with many issues. In this article, we are interested in the impact of synchronization on models design and on their execution. We highlight synchronization problems through model instances then we experimentally analyze the impact of synchronization on large scale test cases

Cells derived from regenerated endothelium of the porcine coronary artery contain more oxidized forms of apolipoprotein-B-100 without a modification in the uptake of oxidized LDL

Increased accumulation of lipoproteins and cholesterol within cells from regenerated endothelium may be responsible for their reported dysfunction. This study compared the presence and uptake of oxidized forms of low-density lipoprotein (LDL) in cells derived from native and regenerated endothelium. Four weeks after balloon denudation, primary cultures of native and regenerated endothelial cells were prepared from porcine coronary arteries. Regenerated endothelium stained more strongly using an antibody against oxidized lipoproteins. The increase in oxidized forms of apolipoprotein-B-100 exhibited by cells from regenerated endothelium was not due to an increase in extracellular-induced oxidation of native LDL, measured as the production of thiobarbituric-acid-reactive substances, being identical in both cell types. Intracellular cholesterol and cholesterol ester content were unchanged in regenerated cells. Using flow cytometry, accumulation of oxidized LDL was investigated further by quantifying the uptake of a mildly oxidized preparation of 1,1’-dioctadecyl-3,3,3’,3-tetramethyl-indocarbocyanine perchlorate-labelled LDL. The parameters of uptake, EC50 and Emax, were not different between cells from native and regenerated endothelium suggesting that the number of LOX-1 receptors was identical in the two cell types. Moreover, a negative correlation between the increased uptake of acetylated LDL and decreased cGMP production in response to bradykinin was observed in cells from regenerated endothelium. Thus, the increased incorporation of modified LDL and their intracellular oxidation could be responsible for the alteration in NO production. The presence of oxidized forms of LDL may be a marker of endothelium regeneration and could be involved in the endothelial dysfunction of pig coronary arteries 4 weeks after balloon denudation