Reproducible and User-Controlled Software Environments in HPC with Guix

Support teams of high-performance computing (HPC) systems often find themselves between a rock and a hard place: on one hand, they understandably administrate these large systems in a conservative way, but on the other hand, they try to satisfy their users by deploying up-to-date tool chains as well as libraries and scientific software. HPC system users often have no guarantee that they will be able to reproduce results at a later point in time, even on the same system-software may have been upgraded, removed, or recompiled under their feet, and they have little hope of being able to reproduce the same software environment elsewhere. We present GNU Guix and the functional package management paradigm and show how it can improve reproducibility and sharing among researchers with representative use cases.Comment: 2nd International Workshop on Reproducibility in Parallel Computing (RepPar), Aug 2015, Vienne, Austria. http://reppar.org

Tailoring the etchability of aluminium foil by laser interference metallurgy : control of pit initiation sites for high-voltage aluminium capacitor applications

During the last decades, different surface patterning techniques have been developed to produce structures in the nano/submicron scale, Laser Interference Metallurgy (LIMET) being one of them. LIMET allows the production of direct periodic arrays over large areas by using the interference of several laser beams. This technique is an attractive tool to improve the etching process of anode aluminium during the manufacturing of high-voltage aluminium capacitors, where aluminium foils are etched so as to develop a high surface area thereby achieving the maximum possible capacitance. The aim of this work was to develop a method for controlling the pit-site distribution during the etching process of aluminium foil. For this purpose, the mechanism that governs the surface patterning of metals and the physical/chemical changes induced by LIMET were investigated. It was demonstrated that the main forces producing the periodic structures on metallic surfaces are surface-tension-driven flow and recoil pressure. Moreover, the impact on aluminium etchability of ordered local oxidation and incorporation of small quantities of Pb and Cu was studied. It was found that periodic surface activation and/or passivation improve the pit distribution of the exposed aluminium. In all systems studied, the etching process followed the ordered array generated by laser interference. Finally, 3D quantitative characterisation of etched structures was performed using FIB tomography.In den letzten Jahren wurden verschiedene Oberflächenbehandlungstechniken entwickelt, um Strukturen im Nano/Submikrometer-Bereich zu erzeugen, zu denen auch die Laser Interferenz Metallurgie (LIMET) zählt. LIMET ermöglicht die direkte Erzeugung von periodischen, großflächigen Strukturen durch die Interferenz einzelner Laserstrahlen. Diese Technik stellt ein vielversprechendes Werkzeug dar, um den Ätzprozess der Aluminiumanode für Hochspannungskondensatoren zu verbessern. Bei der Herstellung von Aluminium-Elektrolytkondensatoren werden Aluminiumfolien geätzt, um eine Vergrößerung der Oberfläche herbeizuführen und damit eine deutlich höhe Kapazität zu erzielen. Das Ziel dieser Arbeit ist die Entwicklung eines Verfahrens zur Kontrolle der örtlichen Verteilung der beim Aluminiumätzprozess entstehenden Gruben. Es wurde demonstriert, dass die wichtigsten Effekte bei der Herstellung periodischer Strukturen sowohl der Oberflächenspannungsgradient als auch der Rückstoßdruck sind. Des Weiteren wurden die Auswirkungen von lokaler Oxidation und Einbau geringer Mengen von Pb und Cu auf die Ätzbarkeit von Aluminium untersucht. Es hat sich gezeigt, dass periodische Aktivierung und/oder Passivierung der Oberfläche die Grubenverteilung bei exponiertem Aluminium verbessert. In allen Fällen folgte der Ätzvorgang den durch Laserinterferenz vorgegebenen geordneten Mustern. Schließlich wurden die geätzten Strukturen mittels einer quantitativen 3D FIB-Tomographie charakterisiert

Plasma-material interaction and electrode degradation in high voltage ignition discharges

Erosion of material caused by electrical discharges takes place in many technical applications. Particularly, in spark plugs, the durability is mainly determined by the electrode erosion caused by ignition discharges. A better understanding of the wear mechanisms will help in developing new electrode materials with enhanced resistance against spark erosion. In this work, different aspects of the complex interaction between the plasma of the ignition discharge and the electrode are investigated based on experimental observations and simulations. The discharge mode behavior is quantitatively analyzed with regard to the arc and glow phase fractions for different electrode materials and conditions of pressure and gas. The influence of these parameters on the discharge is discussed. This work especially focuses on the formation of microscopic erosion craters on the electrode surface. Their morphology and microstructure are characterized by means of FIB/SEM dual beam techniques. The depth of modifications and the extent of the molten region are determined. To complete these experimental observations, thermal analysis of the crater formation is performed using analytical models and FEM simulations. Characteristic values of time, power density and current involved in the crater formation are estimated. These values are related to the electrical characteristic of the spark, and the effects of the discharge phases on the electrode surface degradation are discussed.Die Erosion von Materialien, die von einer elektrischen Entladung hervorgerufen wird, tritt in zahlreichen technischen Anwendungen auf. Auch die Lebensdauer einer Zündkerze wird durch die von den Zündentladungen verursachte Erosion an Elektrodenmaterialien maßgeblich bestimmt. Ein besseres Verständnis der Verschleißmechanismen ist von großer Bedeutung, um maßgeschneiderte Werkstoffe mit verbessertem Funkenerosionsverhalten zu entwickeln. In dieser Arbeit werden verschiedene Aspekte der komplexen Wechselwirkung zwischen dem Plasma der Zündentladung und der Elektrode anhand von experimentellen Beobachtungen und Simulationen erforscht. Das Entladungsverhalten (Bogen- und Glimmanteil) wird für verschiedene Elektrodenwerkstoffe, Gas-, und Druckbedingungen quantitativ untersucht. Die Morphologie und Mikrostruktur von Erosionskratern werden mit Hilfe von FIB/REM Dual-Beam-Techniken charakterisiert. Die mikrostrukturellen Veränderungen des Materials unterhalb der Oberfläche und insbesondere der Schmelzbadgröße werden bestimmt. Zur Ergänzung der experimentellen Beobachtungen, wird eine thermische Analyse der Kraterbildung mittels analytischen Modellen und FEM-Simulationen durchgeführt. Charakteristische Werte des Kraterbildungsprozesses wie z.B. die Wärmezufuhr, der Strom, und die Wechselwirkungsdauer werden bestimmt und in Bezug auf die verschiedenen Phasen der Zündentladung diskutiert

Relaxed Synchronization with Ordered Read-Write Locks

This article is accepted for publication in the post-proceedings of the Workshop on Algorithms and Programming Tools for Next-Generation High-Performance Scientific Software (HPSS) 2011, held in the context of Euro-Par 2011, August 29, 2011, Bordeaux, France.International audienceThis paper promotes the first stand-alone implementation of our adaptive tool for synchronization ''ordered read-write locks'', ORWL. It provides new synchronization methods for resource oriented parallel or distributed algorithms for which it allows an implicit deadlock-free and equitable control of a protected resource and provides means to couple lock objects and data tightly. A typical application that uses this framework will run a number of loosely coupled tasks that are exclusively regulated by the data flow. We conducted experiments to prove the validity, efficiency and scalability of our implementation.Ce papier présente la première implantation directe de notre outil adaptatif de synchronisation, " ordered read-write locks " (ORWL). Il fournit des méthodes nouvelles de synchronisation pour des algorithmes parallèle ou reparties orientés ressources. Il permet un contrôle implicite d'une ressource protégée qui est équitable et sans interblocage et fournit des moyens de coupler des objets de verrou et des données de façon stricte. Une application typique qui utilise ce cadre va effectuer un nombre de tâches couplées de façon relâchée et qui seraient exclusivement régulés par le flot des données. Nous avons conduit des expériences qui prouvent la validité, l'efficacité et le passage à l'échelle de notre implantation

Kadeploy3: Efficient and Scalable Operating System Provisioning for HPC Clusters

Operating system provisioning is a common and critical task in cluster computing environments. The required low-level operations involved in provisioning can drastically decrease the performance of a given solution, and maintaining a reasonable provisioning time on clusters of 1000+ nodes is a significant challenge. We present Kadeploy3, a tool built to efficiently and reliably deploy a large number of cluster nodes. Since it is a keystone of the Grid'5000 experimental testbed, it has been designed not only to help system administrators install and manage clusters but also to provide testbed users with a flexible way to deploy their own operating systems on nodes for their own experimentation needs, on a very frequent basis. In this paper we detail the design principles of Kadeploy3 and its main features, and evaluate its capabilities in several contexts. We also share the lessons we have learned during the design and deployment of Kadeploy3 in the hope that this will help system administrators and developers of similar solutions

Emulation at Very Large Scale with Distem

International audienceProspective exascale systems and large-scale cloud infrastructures are composed of dozens of thousands of nodes. Evaluating applications that target such environments is extremely difficult. In this paper, we present an extension of the Distem emulator to allow experimenting on very large scale emulated platforms thanks to the use of a VXLAN overlay network. We demonstrate that Distem is capable of emulating 40,000 virtual nodes on 168 physical nodes, and use the resulting emulated environment to compare two efficient parallel command runners: TakTuk and ClusterShell

Efficient and Scalable OS Provisioning with Kadeploy 3

National audienceKadeploy3 est un logiciel permettant de déployer de manière efficace et fiable des ensembles de machines, notamment dans le contexte des clusters de calcul à haute performance. Kadeploy3 permet de déployer des milliers de machines grâce à l'utilisation de mécanismes de diffusion d'image et d'exécution de commande particulièrement optimisés pour la grande échelle. Il permet aussi de résister correctement aux pannes et erreurs inévitables à cette échelle grâce à un moteur de workflow proposant des mécanismes de reprise sur erreur. Une grande attention est également portée à l'utilisabilité et à l'adaptabilité de Kadeploy3, avec notamment la gestion d'une bibliothèque d'environnements, et une gestion fine des droits. Le poster détaille différents aspects de Kadeploy, notamment: - ses fonctionnalités principales ; - sa capacité à passer à l'échelle ; - sa résistance aux pannes ; - quelques éléments d'évaluation. Kadeploy est diffusé sous licence libre, et est activement développé et maintenu par Inria Nancy Grand-Est

Kadeploy3: Efficient and Scalable Operating System Provisioning for Clusters

International audienceInstalling an operating system can be very tedious when it must be repro- duced on several computers, for instance, on large scale clusters. Since it is not realistic to install the nodes independently, disk cloning or imaging with tools such as Clonezilla[1], Rocks [5], SystemImager [6] or xCAT [8] is a com- mon approach. In that case the administrator must keep updated only one node (sometimes called golden node), that will be replicated to other nodes. This article presents Kadeploy3, a tool designed to perform operating system provi- sioning using disk imaging and cloning. Thanks to its e ciency, scalability, and reliability, it is particularly suited for large scale clusters

Performance evaluation of containers for HPC

International audienceContainer-based virtualization technologies such as LXC or Docker have gained a lot of interest recently, especially in the HPC context where they could help to address a number of long-running issues. Even if they have proven to perform better than full-fledged, hypervisor-based, virtualization solutions, there are still a lot of questions about the use of container solutions in the HPC context. This paper evaluates the performance of Linux-based container solutions that rely on cgroups and namespaces using the NAS parallel benchmarks, in various configurations. We show that containers technology has matured over the years, and that performance issues are being solved

Porting the Distem Emulator to the CloudLab and Chameleon testbeds

The Distem emulator was designed in the context of the Grid'5000testbed. In this paper, we describe the experience of porting Distem totwo testbeds: CloudLab and Chameleon, in order to uncover possibleissues when deploying Distem on platforms different from Grid'5000. Italso provides some insight on differences between the design of each ofthose three testbeds, and their impact on experimenters