Scaling of Distributed Multi-Simulations on Multi-Core Clusters

International audienceDACCOSIM is a multi-simulation environment for continuous time systems, relying on FMI standard, making easy the design of a multi-simulation graph, and specially developed for multi-core PC clusters, in order to achieve speedup and size up. However, the distribution of the simulation graph remains complex and is still the responsibility of the simulation developer. This paper introduces DACCOSIM parallel and distributed architecture, and our strategies to achieve efficient multi-simulation graph distribution on multi-core clusters. Some performance experiments on two clusters, running up to 81 simulation components (FMU) and using up to 16 multi-core computing nodes, are shown. Performances measured on our faster cluster exhibit a good scalability, but some limitations of current DACCOSIM implementation are discussed

Toward an Accurate and Fast Hybrid Multi-Simulation with the FMI-CS Standard

International audienceMulti-simulation in the context of future smart electrical grids consists in associating components modeling different physical domains, but also their local or global control. Our DACCOSIM multi-simulation environment is based on the version 2.0 of the FMI-CS (Functional Mock-up Interface for Co-Simulation) standard maintained by the Modelica Association. It has been specifically designed to run large-scale and complex systems on a single PC or a cluster of multicore nodes. But it is quite challenging to accurately simulate FMUs-composed systems involving predictable and unpredictable events while preserving the system overall performance. This paper presents some additions to the FMI-CS standard aiming to improve the accuracy and the performance of distributed multi-simulations involving a mix of both time steps and various kinds of events. The proposed FMI-CS primitives are explained, as well as the Master Algorithm strategies to exploit them efficiently

Multi-agent Multi-Model Simulation of Smart Grids in the MS4SG Project

International audienceThis paper illustrates how the multi-agent approach, or paradigm, can help in the modeling and the simulation of smart grids in the context ofMS4SG (a joint project between LORIA-INRIA and EDF R&D). Smart grids simulations need to integrate together pre-existing and heterogeneous models and their simulation software; for example modeling tools of the power grids, of telecommunication networks, and of the information and decision systems. This paper describes the use of MECSYCO as a valid approach to integrate these heterogeneous models in a multi-agent smart grid simulation platform. Several use cases show the ability of MECSYCO to effectively take into account the requirements of smart grids simulation in MS4SG

Smart Grids Simulation with MECSYCO

International audienceThese demonstrations are part of the MS4SG project and show the current results of the DEVS-based platform called MECSYCO (Multi-agent Environment for Complex SYstems CO-simulation), formerly named AA4MM (Agents & Artifacts for Multi-Modeling), in the context of smart grids simulation with different use cases based on real scenarios

Enhanced articular cartilage by human mesenchymal stem cells in enzymatically mediated transiently RGDS-functionalized collagen-mimetic hydrogels

Recapitulation of the articular cartilage microenvironment for regenerative medicine applications faces significant challenges due to the complex and dynamic biochemical and biomechanical nature of native tissue. Towards the goal of biomaterial designs that enable the temporal presentation of bioactive sequences, recombinant bacterial collagens such as Streptococcal collagen-like 2 (Scl2) proteins can be employed to incorporate multiple specific bioactive and biodegradable peptide motifs into a single construct. Here, we first modified the backbone of Scl2 with glycosaminoglycan-binding peptides and cross-linked the modified Scl2 into hydrogels via matrix metalloproteinase 7 (MMP7)-cleavable or non-cleavable scrambled peptides. The cross-linkers were further functionalized with a tethered RGDS peptide creating a system whereby the release from an MMP7-cleavable hydrogel could be compared to a system where release is not possible. The release of the RGDS peptide from the degradable hydrogels led to significantly enhanced expression of collagen type II (3.9-fold increase), aggrecan (7.6-fold increase), and SOX9 (5.2-fold increase) by human mesenchymal stem cells (hMSCs) undergoing chondrogenesis, as well as greater extracellular matrix accumulation compared to non-degradable hydrogels (collagen type II; 3.2-fold increase, aggrecan; 4-fold increase, SOX9; 2.8-fold increase). Hydrogels containing a low concentration of the RGDS peptide displayed significantly decreased collagen type I and X gene expression profiles, suggesting a major advantage over either hydrogels functionalized with a higher RGDS peptide concentration, or non-degradable hydrogels, in promoting an articular cartilage phenotype. These highly versatile Scl2 hydrogels can be further manipulated to improve specific elements of the chondrogenic response by hMSCs, through the introduction of additional bioactive and/or biodegradable motifs. As such, these hydrogels have the possibility to be used for other applications in tissue engineering. Statement of Significance Recapitulating aspects of the native tissue biochemical microenvironment faces significant challenges in regenerative medicine and tissue engineering due to the complex and dynamic nature of the tissue. The ability to take advantage of, mimic, and modulate cell-mediated processes within novel naturally-derived hydrogels is of great interest in the field of biomaterials to generate constructs that more closely resemble the biochemical microenvironment and functions of native biological tissues such as articular cartilage. Towards this goal, the temporal presentation of bioactive sequences such as RGDS on the chondrogenic differentiation of human mesenchymal stem cells is considered important as it has been shown to influence the chondrogenic phenotype. Here, a novel and versatile platform to recreate a high degree of biological complexity is proposed, which could also be applicable to other tissue engineering and regenerative medicine applications

Calcul de fiabilité dynamique par simulation de Monte-Carlo : gains apportés par la cosimulation

International audienceCet article présente l'intérêt de la cosimulation pour les études de fiabilité de système. On rappelle tout d'abord les difficultés rencontrées dans certains cas d'étude de fiabilité comme le « heated tank » qui nécessite de combiner modélisation fonctionnelle et simulation de Monte Carlo pour générer les pannes (fiabilité hybride). A partir d'un modèle sous Modelica du « heated tank » un fichier FMU est généré. La cosimulation avec les outils DNG permet dans un temps acceptable de faire de nombreuses simulations de fiabilité pour converger vers des résultats statiquement significatifs. On montre un exemple de 100.000 instances sur le cas du « heated tank » pour un temps de calcul de 175 secondes

L'interopérabilité dans les postes PCCN

Colloque avec actes et comité de lecture.Le développement et les performances des technologies dans le domaine des réseaux de communication et des systèmes informatiques autorisent un recours de plus en plus systématique au développement d'applications distribuées plutôt que centralisées. Un système donné peut ainsi être composé de sous-systèmes conçus et développés par des constructeurs différents. Bien que séduisante sous l'angle technico-économique, une telle solution ne peut-être envisageable que si l'interopérabilité entre les différents sous-systèmes est garantie et vérifiée. Cette interopérabilité est essentiellement prouvé grâce à deux moyens complémentaires : · a priori, la modélisation formelle et non ambigüe du comportement fonctionnel de chaque sous-système; · a posteriori, la vérification du respect de cette modélisation par le sous-système. Après une rapide présentation du problème général évoqué ci-dessus, ce papier expose plus précisément le cas du projet PCCN, dans le cadre de la définition du nouveau palier de Postes Source. La solution, en cours de développement par EDF, sera présentée suivant le canevas ci-dessous : · Un protocole de messagerie a été défini à partir des contraintes imposées par les besoins du niveau applicatif et par ceux liés à la qualité de service; · Ce protocole a été modélisé et validé avec SDL (Spécification and Description Language ITU-T Z100 and Z106). Il est utilisé au dessus d'une pile de communication classique composée des standards ETHERNET, UDP/IP, SNMP et TFTP; · La bonne implantation du protocole peut ensuite être évaluée grâce à la génération de séquences de tests (appelés Tests de Conformité) issues directement et automatiquement de la modélisation formelle SDL. Cette solution sera introduite en normalisation à la CEI (Commission Electrotechnique Internationale). l'intérêt de cette solution sera expliqué, aussi bien au niveau technique et économique qu'au niveau stratégique

Synthesis and feedback on the distribution and parallelization of FMI-CS-based co-simulations with the DACCOSIM platform

International audienceA co-simulation applied to Smart Grids consists of grouping in the same setting models of physical components (among other electrical ones) and models of control units (including communication devices). Combining these models needs to use a generic and robust co-simulation environment instead of developing a specific one. In this context, we developed the DACCOSIM 2017 co-simulation platform based on FMI-CS (Functional Mock-up Interface for CoSimulation) standard to simulate the physical components of a Smart Grid. These components represent the most CPU-consuming part of the co-simulation. However, the tasks of FMI-CS-based applications (FMUs) are exposed as heterogeneous gray boxes with no information concerning their computation and communication volumes. Moreover, all these FMUs frequently communicate with each other by sending a lot of small messages. Consequently, the deployment of an FMI-CS based co-simulation on a distributed architecture is a complex task carried out by DACCOSIM 2017. This paper introduces the development of DACCOSIM-2017, and its experiment on distributed architectures

Assessing scalability of a low-voltage distribution grid co-simulation through functional mock-up interface

© 2019, © 2019 International Building Performance Simulation Association (IBPSA). State-of-the-art Modelica tools for modelling and simulating multi-physical systems have reached certain maturity among the building physics community. Hence, simulation is widely used for control, sizing and performance assessment of energy systems. However, serious efficiency issues arise for large-scale models. This article proposes a practical application of co-simulation methods on detailed district energy systems. The aim of this study is to assess performance and scalability of co-simulation through functional mock-up interfaces on a detailed and multi-physical district model. In particular, we propose a comparative analysis between classical simulation and co-simulation methods and a scalability analysis on a growing number of buildings. The models have been implemented using Modelica language and the OpenIDEAS library. A decomposition approach is taken for modelling the entire system, while stochasticity in the inputs is taken into account. Results are presented for various integration scenarios, including a classical integrated simulation for reference and co-simulations involving different master-algorithms within Dymola and DACCOSIM 2017. Scenarios are compared in terms of speed-up and accuracy of principal physical quantities representing key performance indicators such as indoor temperature, current and voltage at building's connection. The analysis shows that co-simulation can run up to 90 times faster than the integrated simulation for 24 buildings, while ensuring acceptable accuracy.status: publishe

Assessing scalability of a low-voltage distribution grid co-simulation through Functional Mockup Interface

International audienceState-of-the-art Modelica tools for modeling and simulating multi-physical systems have reached certain maturity among the building physics community. Hence, simulation is widely used for control, sizing and performance assessment of energy systems. However, serious efficiency issues arise for large-scale models. This article proposes a practical application of co-simulation methods on detailed district energy systems. The aim of this study is to assess performance and scalability of co-simulation through Functional Mock-up Interfaces on a detailed and multi-physical district model. In particular, we propose a comparative analysis between classical simulation and co-simulation methods and a scalability analysis on a growing number of buildings. The models have been implemented using Modelica language and the OpenIDEAS library. A decomposition approach is taken for modeling the entire system, while stochasticity in the inputs is taken into account. Results are presented for various integration scenarios, including a classical integrated simulation for reference and co-simulations involving different master-algorithms within Dymola and DACCOSIM 2017. Scenarios are compared in terms of speed-up and accuracy of principal physical quantities representing key performance indicators such as indoor temperature, current and voltage at building's connection. The analysis shows that co-simulation can run up to 90 times faster than the integrated simulation for 24 buildings, while ensuring acceptable accuracy