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See detailAutomatic Software Tuning of Parallel Programs for Energy-Aware Executions
Varrette, Sébastien UL; Pinel, Frédéric UL; Kieffer, Emmanuel UL et al

in Proc. of 13th Intl. Conf. on Parallel Processing and Applied Mathematics (PPAM 2019) (2019, December)

For large scale systems, such as data centers, energy efficiency has proven to be key for reducing capital, operational expenses and environmental impact. Power drainage of a system is closely related to ... [more ▼]

For large scale systems, such as data centers, energy efficiency has proven to be key for reducing capital, operational expenses and environmental impact. Power drainage of a system is closely related to the type and characteristics of workload that the device is running. For this reason, this paper presents an automatic software tuning method for parallel program generation able to adapt and exploit the hardware features available on a target computing system such as an HPC facility or a cloud system in a better way than traditional compiler infrastructures. We propose a search based approach combining both exact methods and approximated heuristics evolving programs in order to find optimized configurations relying on an ever-increasing number of tunable knobs i.e., code transformation and execution options (such as the num- ber of OpenMP threads and/or the CPU frequency settings). The main objective is to outperform the configurations generated by traditional compiling infrastructures for selected KPIs i.e., performance, energy and power usage (for both for the CPU and DRAM), as well as the runtime. First experimental results tied to the local optimization phase of the proposed framework are encouraging, demonstrating between 8% and 41% improvement for all considered metrics on a reference benchmark- ing application (i.e., Linpack). This brings novel perspectives for the global optimization step currently under investigation within the presented framework, with the ambition to pave the way toward automatic tuning of energy-aware applications beyond the performance of the current state-of-the-art compiler infrastructures. [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 - 2eme (2019)

Une blockchain (chaîne de blocs) est une application informatique qui utilise des techniques cryptographiques permettant à des entités de réaliser entre elles des opérations sans l'intervention d'un tiers ... [more ▼]

Une blockchain (chaîne de blocs) est une application informatique qui utilise des techniques cryptographiques permettant à des entités de réaliser entre elles des opérations sans l'intervention d'un tiers de confiance (banques, notaires...). Les blockchains se répandent dans l'économie sous forme par exemple de nouvelles monnaies (bitcoins, ether...), mais aussi de contrats ou de certifications dans les assurances, dans les affaires (smart contracts), dans le droit... Ces technologies de rupture ne sont pas simples à comprendre que ce soit dans leur fonctionnement informatique (horodatage et immutabilité des blocs) ou dans leurs conséquences pour l'utilisateur (valeur de la preuve, recours possibles...). La meilleure façon d'aborder ce sujet complexe est de répondre point par point aux multiples questions que les utilisateurs potentiels se posent. [less ▲]

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See detailBest Practices for Cloud Migration and Service Level Agreement Compliances
Ibrahim, Abdallah Ali Zainelabden Abdallah UL; Varrette, Sébastien UL; Niessen, Frederic

Report (2019)

Dell Technologies is one of the oldest Information Technology (IT) companies that involved in ICT transformation. ICT transformation is the process of modifying and adjusting the companies IT systems and ... [more ▼]

Dell Technologies is one of the oldest Information Technology (IT) companies that involved in ICT transformation. ICT transformation is the process of modifying and adjusting the companies IT systems and infrastructure. IT transformation is a multi-layer interdisciplinary process which involves typically changes to network architecture, hardware, software, data protection, i.e how data is stored and accessed. The transformation of the business workload and IT systems is the process of rip and replace and Dell is now aiming at guiding their customers in this challenging process. Indeed, Dell Technologies is providing a broad range of IT solutions and services such as data storage, protection, servers and infrastructure, networking, and cloud solutions. Concerning the last type of offer, Dell is providing public, private and hybrid cloud solutions and also coupled with cloud consulting and management services. In this context, the main objective of this work is to help Dell Technologies to come up with a guidelines document for its customers detailing the standards, migration procedures and the importance of smart Information and Communications Technology (ICT) (Cloud Computing (CC)) involved in business transition towards cloud-based solutions. Of course, it is intended for this document to serve as a fair basis to evaluate the offers of multiple cloud providers, while helping to understand the provided Service Level Agreements (SLAs) and the way they are enforced and evaluated by using the International Organization for Standardization (ISO) standards’ such as ISO/IEC DIS 19086, Information Technology (IT)- CC Service Level Agreement (SLA) framework and ISO/IEC DIS 22624, IT- CC taxonomy based data handling for cloud services [less ▲]

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See detailAmazon Elastic Compute Cloud (EC2) versus In-House HPC Platform: A Cost Analysis
Emeras, Joseph; Varrette, Sébastien UL; Plugaru, Valentin UL et al

in IEEE Transactions on Cloud Computing (2019), 7(2), 456-468

Abstract—While High Performance Computing (HPC) centers continuously evolve to provide more computing power to their users, we observe a wish for the convergence between Cloud Computing (CC) and High ... [more ▼]

Abstract—While High Performance Computing (HPC) centers continuously evolve to provide more computing power to their users, we observe a wish for the convergence between Cloud Computing (CC) and High Performance Computing (HPC) platforms, with the commercial hope to see Cloud Computing (CC) infrastructures to eventually replace in-house facilities. If we exclude the performance point of view where many previous studies highlight a non-negligible overhead induced by the virtualization layer at the heart of every Cloud middleware when running a HPC workload, the question of the real cost-effectiveness is often left aside with the intuition that, most probably, the instances offered by the Cloud providers are competitive from a cost point of view. In this article, we wanted to assert (or infirm) this intuition by analyzing what composes the Total Cost of Ownership (TCO) of an in-house HPC facility operated internally since 2007. This Total Cost of Ownership (TCO) model is then used to compare with the induced cost that would have been required to run the same platform (and the same workload) over a competitive Cloud IaaS offer. Our approach to address this price comparison is three-fold. First we propose a theoretical price-performance model based on the study of the actual Cloud instances proposed by one of the major Cloud IaaS actors: Amazon Elastic Compute Cloud (EC2). Then, based on the HPC facility TCO analysis we propose a hourly price comparison between our in-house cluster and the equivalent EC2 instances. Finally, based on the experimental benchmarking on the local cluster and on the Cloud instances we propose an update of the former theoretical price model to reflect the real system performance. The results obtained advocate in general for the acquisition of an in-house HPC facility, which balances the common intuition in favor of Cloud Computing platforms, would they be provided by the reference Cloud provider worldwide. [less ▲]

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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 Zomaya, A. Y.; Carretero, J.; Jeannot, E. (Eds.) Ultrascale Computing Systems (2019)

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 ▲]

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See detailEnergy aware ultrascale systems
Oleksiak, Ariel; Lefèvre, Laurent; Alonso, Pedro et al

in Carretero, J.; Jeannot, E.; Zomaya, A.Y. (Eds.) Ultrascale Computing Systems (2019)

Energy consumption is one of the main limiting factors for the design of ultrascale infrastructures. Multi-level hardware and software optimizations must be designed and explored in order to reduce energy ... [more ▼]

Energy consumption is one of the main limiting factors for the design of ultrascale infrastructures. Multi-level hardware and software optimizations must be designed and explored in order to reduce energy consumption for these largescale equipment. This chapter addresses the issue of energy efficiency of ultrascale systems in front of other quality metrics. The goal of this chapter is to explore the design of metrics, analysis, frameworks and tools for putting energy awareness and energy efficiency at the next stage. Significant emphasis will be placed on the idea of “energy complexity,” reflecting the synergies between energy efficiency and quality of service, resilience and performance, by studying computation power, communication/data sharing power, data access power, algorithm energy consumption, etc. [less ▲]

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See detailA Full-Cost Model for Estimating the Energy Consumption of Computing Infrastructures
Orgerie, Anne-Cecile; Varrette, Sébastien UL

in Zomaya, A. Y; Carretero, J.; Jeannot, E. (Eds.) Ultrascale Computing Systems (2019)

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 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 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 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: 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 ▲]

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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: 88 (9 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 ▲]

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See detailLuxembourg Proposals for Large Scale Architectures for Data Science
Varrette, Sébastien UL

Speeches/Talks (2018)

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See detailOn Verifying and Assuring the Cloud SLA by Evaluating the Performance of SaaS Web Services Across Multi-cloud Providers
Ibrahim, Abdallah Ali Zainelabden Abdallah UL; Varrette, Sébastien UL; Bouvry, Pascal UL

in 48th Annual IEEE/IFIP Intl. Conf. on Dependable Systems and Networks Workshops (DNS'18) (2018, June)

Detailed reference viewed: 81 (9 UL)