References of "Varrette, Sébastien 50003258"
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See detailSecurity, reliability and regulation compliance in Ultrascale Computing System
Bouvry, Pascal UL; Varrette, Sébastien UL; Wasim, Muhammad Umer UL et al

in Carretero, J.; Jeannot, E. (Eds.) Ultrascale Computing Systems (2018)

Ultrascale Computing Systems (UCSs) are envisioned as large-scale complex systems joining parallel and distributed computing systems that will be two to three orders of magnitude larger than today’s ... [more ▼]

Ultrascale Computing Systems (UCSs) are envisioned as large-scale complex systems joining parallel and distributed computing systems that will be two to three orders of magnitude larger than today’s systems (considering the number of Central Process Unit (CPU) cores). It is very challenging to find sustainable solutions for UCSs due to their scale and a wide range of possible applications and involved technologies. For example, we need to deal with heterogeneity and cross fertilization among HPC, large-scale distributed systems, and big data management. One of the challenges regarding sustainable UCSs is resilience. Another one, which attracted less interest in the literature but becomes more and more crucial with the expected convergence with the Cloud computing paradigm, is the notion of regulation in such system to assess the Quality of Service (QoS) and Service Level Agreement (SLA) proposed for the use of these platforms. This chapter covers both aspects through the reproduction of two articles: [1] and [2]. [less ▲]

Detailed reference viewed: 67 (12 UL)
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See detailA Full-Cost Model for Estimating the Energy Consumption of Computing Infrastructures
Orgerie, Anne-Cecile; Varrette, Sébastien UL

in Carretero, J.; Jeannot, E. (Eds.) Ultrascale Computing Systems (2018)

Since its advent in the middle of the 2000’s, the Cloud Computing (CC) paradigm is increasingly advertised as a price-effective solution to many IT problems. This seems reasonable if we exclude the pure ... [more ▼]

Since its advent in the middle of the 2000’s, the Cloud Computing (CC) paradigm is increasingly advertised as a price-effective solution to many IT problems. This seems reasonable if we exclude the pure performance point of view as many studies highlight a non-negligible overhead induced by the virtualization layer at the heart of every Cloud middleware when subjected to an High Performance Computing (HPC) workload. When this is the case, traditional HPC and Ultrascale computing systems are required, and then comes the question of the real cost-effectiveness, especially when comparing to instances offered by the Cloud providers. In this section, and inspired by the work proposed in [1], we propose a Total Cost of Ownership (TCO) analysis of an in-house academic HPC facility of medium-size (in particular the one operated at the University of Luxembourg since 2007, or within the Grid’5000 project [2]), and compare it with the investment that would have been required to run the same platform (and the same workload) over a competitive Cloud IaaS offer. [less ▲]

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See detailHybrid MPI+OpenMP Implementation of eXtended Discrete Element Method
Mainassara Chekaraou, Abdoul Wahid UL; Rousset, Alban UL; Besseron, Xavier UL et al

in Proc. of the 9th Workshop on Applications for Multi-Core Architectures (WAMCA'18), part of 30th Intl. Symp. on Computer Architecture and High Performance Computing (SBAC-PAD 2018) (2018, September)

The Extended Discrete Element Method (XDEM) is a novel and innovative numerical simulation technique that ex- tends classical Discrete Element Method (DEM) (which simulates the motion of granular material ... [more ▼]

The Extended Discrete Element Method (XDEM) is a novel and innovative numerical simulation technique that ex- tends classical Discrete Element Method (DEM) (which simulates the motion of granular material), by additional properties such as the chemical composition, thermodynamic state, stress/strain for each particle. It has been applied successfully to numerous industries involving the processing of granular materials such as sand, rock, wood or coke [16], [17]. In this context, computational simulation with (X)DEM has become a more and more essential tool for researchers and scientific engineers to set up and explore their experimental processes. However, increasing the size or the accuracy of a model requires the use of High Performance Computing (HPC) platforms over a parallelized implementation to accommodate the growing needs in terms of memory and computation time. In practice, such a parallelization is traditionally obtained using either MPI (distributed memory computing), OpenMP (shared memory computing) or hybrid approaches combining both of them. In this paper, we present the results of our effort to implement an OpenMP version of XDEM allowing hybrid MPI+OpenMP simulations (XDEM being already parallelized with MPI). Far from the basic OpenMP paradigm and recommendations (which simply summarizes by decorating the main computation loops with a set of OpenMP pragma), the OpenMP parallelization of XDEM required a fundamental code re-factoring and careful tuning in order to reach good performance. There are two main reasons for those difficulties. Firstly, XDEM is a legacy code devel- oped for more than 10 years, initially focused on accuracy rather than performance. Secondly, the particles in a DEM simulation are highly dynamic: they can be added, deleted and interaction relations can change at any timestep of the simulation. Thus this article details the multiple layers of optimization applied, such as a deep data structure profiling and reorganization, the usage of fast multithreaded memory allocators and of advanced process/thread-to-core pinning techniques. Experimental results evaluate the benefit of each optimization individually and validate the implementation using a real-world application executed on the HPC platform of the University of Luxembourg. Finally, we present our Hybrid MPI+OpenMP results with a 15%-20% performance gain and how it overcomes scalability limits (by increasing the number of compute cores without dropping of performances) of XDEM-based pure MPI simulations. [less ▲]

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See detailLes blockchains en 50 questions: comprendre le fonctionnement et les enjeux de cette technologie innovante
Dumas, J.-G.; Lafourcade, P.; Tichit, A. et al

Book published by Dunod - 1er (2018)

Depuis l’avènement du bitcoin, les innovations liées à la blockchain sont en plein essor. Cet ouvrage tente d’expliquer le fonctionnement de cette technologie innovante mais aussi ses applications au ... [more ▼]

Depuis l’avènement du bitcoin, les innovations liées à la blockchain sont en plein essor. Cet ouvrage tente d’expliquer le fonctionnement de cette technologie innovante mais aussi ses applications au travers de 50 questions comme: - Qu’est-ce qu’une blockchain ? - Quel est le lien entre bitcoin et blockchains ? - Qui sont les mineurs et que font-ils ? - Qu’est ce qu’un consensus ? - Quelle est la part des cryptomonnaies dans l’économie mondiale ? - Qu’est-ce qu’un contrat intelligent ? - Peut-on faire une blockchain sans bloc ? - Comment les blockchains vont changer le monde de demain ? Les réponses à toutes ces questions et à 42 autres sont dans ce livre. [less ▲]

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See detailPRESENCE: Monitoring and Modelling the Performance Metrics of Mobile Cloud SaaS Web Services
Ibrahim, Abdallah Ali Zainelabden Abdallah UL; Wasim, Muhammad Umer UL; Varrette, Sébastien UL et al

in Mobile Information Systems (2018), 2018(1351386),

Service Level Agreements (SLAs) are defining the quality of the services delivered from the Cloud Services Providers (CSPs) to the cloud customers. The services are delivered on a pay-per-use model. The ... [more ▼]

Service Level Agreements (SLAs) are defining the quality of the services delivered from the Cloud Services Providers (CSPs) to the cloud customers. The services are delivered on a pay-per-use model. The quality of the provided services is not guaranteed by the SLA because it is just a contract. The developments around mobile cloud computing and the advent of edge computing technologies are contributing to the diffusion of the cloud services and the multiplication of offers. Although the cloud services market is growing for the coming years, unfortunately, there is no standard mechanism which exists to verify and assure that delivered services satisfy the signed SLA agreement in an automatic way. The accurate monitoring and modelling of the provided Quality of Service (QoS) is also missing. In this context, we aim at offering an automatic framework named PRESENCE, to evaluate the QoS and SLA compliance of Web Services (WSs) offered across several CSPs. Yet unlike other approaches, PRESENCE aims at quantifying in a fair and by stealth way the performance and scalability of the delivered WS. This article focuses on the first experimental results obtained on the accurate modelisation of each individual performance metrics. Indeed, 19 generated models are provided, out of which 78.9% accurately represent the WS performance metrics for two representative SaaS web services used for the validation of the PRESENCE approach. This opens novel perspectives for assessing the SLA compliance of Cloud providers using the PRESENCE framework. [less ▲]

Detailed reference viewed: 38 (7 UL)
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See detailHigh Performance Computing and Big Data analytics in Luxembourg: Overview and Challenges in the EuroHPC horizon
Besseron, Xavier UL; Varrette, Sébastien UL

Presentation (2018, August)

Accelerating modelling and simulation in the data deluge era requires the appropriate hardware and infrastructure at scale. The University of Luxembourg is active since 2007 to develop its own ... [more ▼]

Accelerating modelling and simulation in the data deluge era requires the appropriate hardware and infrastructure at scale. The University of Luxembourg is active since 2007 to develop its own infrastructure and expertise in the HPC and BD domains. The current state of developments will be briefly reviewed in the context of the national and European HPC strategy in which Luxembourg is starting to play a role. [less ▲]

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See detailPRESENCE: Performance Metrics Models for Cloud SaaS Web Services
Ibrahim, Abdallah Ali Zainelabden Abdallah UL; Wasim, Umer; Varrette, Sébastien UL et al

in Proc. of the 11th IEEE Intl. Conf. on Cloud Computing (CLOUD 2018) (2018, July)

Detailed reference viewed: 40 (8 UL)
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See detailThéorie des Codes : Compression, Cryptage et Correction
Dumas, J.-G.; Roch, J.-L.; Tannier, E. et al

Book published by Dunod - 3rd (2018)

Transmettre des informations sous forme numérique suppose entre autres d’optimiser la taille des messages transmis pour éviter de surcharger les canaux de transmission, d’être capable de rectifier des ... [more ▼]

Transmettre des informations sous forme numérique suppose entre autres d’optimiser la taille des messages transmis pour éviter de surcharger les canaux de transmission, d’être capable de rectifier des erreurs apparues en cours de transmission, de crypter les contenus et d’authentifier les émissaires et les destinataires… L’originalité de cet ouvrage est de présenter tous les fondements mathématiques et informatiques sur lesquels reposent ces techniques. Les notions théoriques présentées sont illustrées par 140 exercices corrigés. Cette 3e édition s’enrichit de compléments sur les infrastructures à clefs publiques (PKI), les courbes elliptiques, les registres à décalage (LFSR), les fonctions de hachage. L’utilisation de la cryptographie dans les applications mobiles (Facebook, Messenger, WhatsApp…) est abordée, et des bonnes pratiques de sécurité sont présentées pour des utilitaires incontournables comme GPG et SSH. [less ▲]

Detailed reference viewed: 14 (0 UL)
See detailUL HPC Tutorial: HPC workflow with sequential jobs
Cartiaux, Hyacinthe UL; Varrette, Sébastien UL; Plugaru, Valentin UL et al

Presentation (2018, June)

Detailed reference viewed: 31 (3 UL)
See detailUL HPC Tutorial: (Advanced) Prototyping with Python
Parisot, Clément UL; Diehl, Sarah UL; Varrette, Sébastien UL et al

Presentation (2018, June)

Detailed reference viewed: 17 (3 UL)
See detailUL HPC Tutorial: Statistical Computing with R
Ginolhac, Aurélien UL; Emeras, Joseph; Varrette, Sébastien UL et al

Presentation (2018, June)

Detailed reference viewed: 39 (16 UL)
See detailUL HPC Tutorial: Advanced Job scheduling with SLURM and OAR
Plugaru, Valentin UL; Varrette, Sébastien UL; Diehl, Sarah UL et al

Presentation (2018, June)

Detailed reference viewed: 27 (2 UL)
See detailUL HPC Tutorial: HPC Containers with Singularity
Plugaru, Valentin UL; Varrette, Sébastien UL; Diehl, Sarah UL et al

Presentation (2018, June)

Detailed reference viewed: 27 (3 UL)