61 research outputs found
Coherent and turbulent processes in the bistable regime around a tandem of cylinders including reattached flow dynamics by means of high-speed PIV
The turbulent flow around two cylinders in tandem at the sub-critical Reynolds number range of order of 105 and pitch to diameter ratio of 3.7 is investigated by using time-resolved Particle Image Velocimetry (TRPIV) of 1 kHz and 8 kHz. The bi-stable flow regimes including a flow pattern I with a strong vortex shedding past the upstream and the downstream cylinder, as well as a flow pattern II corresponding to a weak alternating vortex shedding with reattachment past the upstream cylinder are investigated. The structure of this âreattachment regimeâ has been analyzed in association with the vortex dynamics past the downstream cylinder, by means of POD and phase-average decomposition. These elements allowed interconnection among all the measured PIV planes and hence analysis of the reattachment structure and the flow dynamics past both cylinders. The results highlight fundamental differences of the flow structure and dynamics around each cylinder and provide the âgapâ flow nature between the cylinders. Thanks to a high-speed camera of 8 kHz, the shear-layer vortices tracking has been possible downstream of the separation point and the quantification of their shedding frequency at the present high Reynolds number range has been achieved. This issue is important regarding fluid instabilities involved in the fluidâstructure interaction of cylinder arrays in nuclear reactor systems, as well as acoustic noise generated from the tandem cylinders of a landing gear in aeronautics
FAIL-MPI: How fault-tolerant is fault-tolerant MPI ?
One of the topics of paramount importance in the development of Cluster and Grid middleware is the impact of faults since their occurrence probability in a Grid infrastructure and in large-scale distributed system is actually very high. MPI (Message Passing Interface) is a popular abstraction for programming distributed computation applications. FAIL is an abstract language for fault occurrence description capable of expressing complex and realistic fault scenarios. In this paper, we investigate the possibility of using FAIL to inject faults in a fault-tolerant MPI implementation. Our middleware, FAIL-MPI, is used to carry quantitative and qualitative faults and stress testing
Une para-plateforme pour faire communautĂ© autour de lâenseignement de lâinformatique
Computer science education is a major issue in the training of the adults of tomorrow who will have to enroll in a society where technology is increasingly present. However, for compulsory education in many European countries it has only recently been introduced or is only at the draft stage. The European Commission, aware of the major challenges of digital and computer education, has designed a frame of reference and within this frame of reference, our project more specifically targets the learning of computer science in link with item 3 âDigital content creationâ and 5 âProblem solving â.In this context, the Computer Learning Community project aims to bring French spiking teachers into a community to facilitate the discovery of computer science and the necessary methods and tools for their learning, considering students aged 10 to 18. years. Our platform and related tools allow mutual assistance between teachers and other education professionals through discussions, sharing of experiences and open educational resources.Here, after a brief overview of the existing expression of need, and a presentation of the methodology of a community of practice, we describe the implementation of what we call a âparaâ-platform with is in connection with already existing initiatives, to help them.Experimenting and evaluating this proposal will take place in 2021 and 2020 and constitutes the perspective of this preliminary work.Lâenseignement de lâinformatique est un enjeu majeur dans la formation des adultes de demain qui devront sâinscrire dans une socieÌteÌ ouÌ la technologie est de plus en plus preÌsente. Cependant, pour lâenseignement obligatoire dans de nombreux pays europeÌens, il nâa eÌteÌ que tout reÌcemment introduit ou nâest seulement quâau stade de projet. La Commission europeÌenne, consciente des enjeux majeurs de lâenseignement du numeÌrique et de lâinformatique, a conçu un cadre de reÌfeÌrence et au sein de ces reÌfeÌrentiels, notre projet vise plus particulieÌrement lâapprentissage des sciences informatiques via les points 3 âDigital content creationâ et 5 âProblem solvingâ. Dans ce contexte, le projet de CommunautĂ© d'Apprentissage de l'Informatique vise la mise en communautĂ© dâenseignant·e·s pour leur faciliter la dĂ©couverte de lâinformatique et dâoutils nĂ©cessaires pour son apprentissage aux Ă©lĂšves de 10 Ă 18 ans. Une plateforme et des outils numĂ©riques permettent l'entraide entre enseignant·e·s et autres professionnel·le·s de lâĂ©ducation Ă travers discussions et partages dâexpĂ©riences et de ressources pĂ©dagogiques. Nous discutons ici, aprĂšs un bref panorama de lâexistant de lâexpression des besoins, et de la mĂ©thodologie dâuune communautĂ© de pratique avant de dĂ©crire lâimplĂ©mentation de ce que nous appelons une âparaâ-plateforme qui vient en appui et en lien des plateformes existantes.ExpĂ©rimenter et Ă©valuer cette proposition se fera en 2021 et 2020 et constitue la perspective de ce travail prĂ©liminaire
Enjeux dans la création d'une communauté d'enseignants engagés dans l'apprentissage de l'informatique
International audienceLâaccompagnement des enseignants du primaire et du secondaire en charge de lâenseignement de lâinformatique est un enjeu majeur dans lâintĂ©gration effective de lâenseignement de lâinformatique Ă lâĂ©cole. La formation initiale et continue doit pouvoir permettre dâaccompagner les enseignants dans leur propre apprentissage de lâinformatique et les aider Ă dĂ©velopper leurs connaissances et leurs stratĂ©gies pĂ©dagogiques pour cet enseignement de lâinformatique. Dans ce contexte, lâentraide et le dĂ©veloppement dâun sentiment dâauto-efficacitĂ© doit permettre de sĂ©curiser les enseignants intĂ©grants des activitĂ©s dâapprentissage de lâinformatique Ă lâĂ©cole. Ă cette fin, dans le cadre du projet Erasmus+ CommunautĂ© dâApprentissage de lâInformatique (CAI), nous visons Ă dĂ©velopper une CommunautĂ© de Pratique (CoP) qui puissent permettre le partage, mais aussi le dĂ©veloppement, de pratiques et de ressources pĂ©dagogiques co-construites autour de lâenseignement de lâinformatique Ă lâĂ©cole. Nous dĂ©crivons ici les enjeux de la crĂ©ation de cette CoP et les enjeux pour son dĂ©veloppement et son Ă©valuation
Un espace de formation francophone dédié à l'apprentissage de l'informatique
National audienceLâintroduction de lâenseignement de lâinformatique au lycĂ©e va permettre aux prochaines gĂ©nĂ©rations de maĂźtriser et participer au dĂ©veloppement du numĂ©rique. Le principal enjeu est alors la formation des enseignantes et des enseignants. Comment relever un tel dĂ©fi ?Dâabord en faisant communautĂ© dâapprentissage et de pratique : depuis des semaines dĂ©jĂ en 2021 lâAEIF et le projet CAI contribuent Ă lâaccueil et lâentraide de centaines de collĂšgues en activitĂ© ou en formation, discutant de tous les sujets, partageant des ressources sur un forum dĂ©diĂ© et des listes de discussions.Puis, depuis dĂ©but 2022, en offrant deux formations en ligne :- Une formation aux fondamentaux de lâinformatique, avec un ordre de grandeur de 200 heures de travail, avec les ressources de formation dâinitiation et de perfectionnement. Plus quâun simple "MOOC", ce sont les ressources dâune formation complĂšte, et un accompagnement prĂ©vu pour permettre de bien les utiliser.- Une formation pour apprendre Ă enseigner⊠par la pratique, en co-prĂ©parant les activitĂ©s pĂ©dagogiques des cours Ă venir, en partageant des pratiques didactiques et en prenant un recul pĂ©dagogique, y compris du point de vue de la pĂ©dagogie de lâĂ©galitĂ©.Les personnes dĂ©sireuses de se prĂ©parer au CAPES y trouveront aussi des conseils et des pistes de travail.Si vous nâavez pas envie dâĂȘtre seul·e relativement Ă cet enseignement de lâinformatique et ĂȘtre accompagnĂ© dans les trois ans qui viennent, passez nous voir ce jour-lĂ
Ludification pour la motivation en apprentissage de la programmation
International audienc
Injection de fautes dans les systÚmes distribués
Dans un rĂ©seau constituĂ© de plusieurs milliers d ordinateurs, l apparition de fautes est inĂ©vitable. Etre capable de tester le comportement d un programme distribuĂ© dans un environnement oĂč l on peut contrĂŽler les fautes (comme le crash d un processus) est une fonctionnalitĂ© importante pour le dĂ©ploiement de programmes fiables. Dans cette thĂšse, nous prĂ©sentons FAIL (pour FAult Injection Language), un langage qui permet d Ă©laborer des scĂ©narios de fautes complexes relativement facilement, tout en dĂ©chargeant l utilisateur de l Ă©criture de code de bas niveau. En outre, il est possible de construire des scĂ©narios de fautes probabilistes (pour des tests quantitatifs) ou dĂ©terministes et reproductibles (pour Ă©tudier le comportement de l application dans des cas particuliers). Ensuite, nous prĂ©sentons FCI (FAIL Cluster Implementation), notre injecteur de fautes, qui consiste en un compilateur, une bibliothĂšque d exĂ©cution et une plate-forme pour l injection de fautes dans des applications distribuĂ©es. FCI est capable de s interfacer avec de nombreux langages de programmation sans nĂ©cessiter la modification de leur code source. Nous prĂ©sentons Ă©galement les tests que nous avons conduit sur diffĂ©rentes applications distribuĂ©es.In large scale distributed systems, the occurrence of faults is unavoidable. Being able to control faults (such as the crash of a process) is an important tool to deploy reliable distributed systems. In this thesis, we present FAIL (for Fault Injection Language), a language that permits to elaborate complex fault scenarios easily. It is possible to design probabilistic scenarios (for quantitative tests) as well as deterministic reproduciple ones. We then present FAIL-FCI (FAIL Cluster Implementation), our fault injector, that consists in a compiler, a runtime library, and a middleware platform for distributed fault-injection. FCI can be interfaced with various programming languages and does not require source code modification. We also present various tests we conducted on several distributed applications.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF
A language-driven tool for fault injection in distributed applications
International audienceIn a network consisting of several thousands computers, the occurrence of faults is unavoidable. Being able to test the behavior of a distributed program in an environment where we can control the faults (such as the crash of a process) is an important feature that matters in the deployment of reliable programs. In this paper, we present FAIL (for FAult Injection Language), a language that permits to elaborate complex fault scenarios in a simple way, while relieving the user from writing low level code. Besides, it is possible to construct probabilistic scenarios (for average quantitative tests) or deterministic and reproducible scenarios (for studying the application's behavior in particular cases). We also present FCI, the FAIL cluster implementation, that consists of a compiler, a runtime library and a middleware platform for software fault injection in distributed applications. FCI is able to interface with numerous programming languages without requiring the modification of their source code, and the preliminary tests that we conducted show that its effective impact at runtime is low
Easy Fault Injection and Stress Testing with FAIL-FCI
In a network consisting of several thousands computers, the occurrence of faults is unavoidable. Being able to test the behavior of a distributed program in an environment where we can control the faults (such as the crash of a process) is an important feature that matters in the deployment of reliable programs. In this paper, we extend FAIL-FCI (for Fault Injection Language, and FAIL Cluster Implementation, respectively), a software tool that permits to elaborate complex fault scenarios in a simple way, while relieving the user from writing low level code. In particular, we show that not only we are able to fault-load existing distributed applications (as used in most current papers that address fault-tolerance issues), we are also able to inject qualitative faults, i.e. inject specific faults at very specific moments in the program code of the application under test. Finally, and although this was not the primary purpose of the tool, we are also able to inject specific patterns of workload, in order to stress test the application under test. Interestingly enough, the whole process is driven by a simple unified description language, that is totally independent from the language of the application, so that no code changes or recompilation are needed on the application side
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