WG

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WG Philippe Virouleau: Improving OpenMP compilers and runtimes for task-based applications on NUMA architectures

2016-05-17 – Philippe Virouleau

Title: Improving OpenMP compilers and runtimes for task-based applications on NUMA architectures

Speaker: Philippe Virouleau

Abstract: The most popular architecture for building large-scale shared memory machines nowodays is the NUMA architecture (Non-Uniform Memory Access). In such architecture, the shared memory and cores are split in nodes, physically separated from each others. The memory access time depends on which core wants to access which data, and the distance between the core and the data’s NUMA node. A popular application design to efficiently exploit the parallelism offered by large multi processors architectures is to use fine-grain dependent tasks. In order to successfully use this approach on NUMA architectures, the application’s programmer should take great care of the locality between the task being executed, and the data manipulated by the task. OpenMP is the de-facto standard for shared-memory parallel programming, and the revision 4.0 introduced the tasks with dependencies model, in which the programmer can specify which data are read and/or written by a given task. Having the runtime use these informations is a first step to dynamically improve the application’s performances, however more flexibility could be given to the programmer, e.g. by giving him the possibility to specify which data are important for a given task. This presentation will describe my PhD works, which focus on proposing and evaluating compilers and runtimes extensions to help reduce the impact of NUMA architectures on the application’s performances and scalability.

PDF: WG_160517_avalon_2015

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WG Issam Raïs: Towards Green Exascale Computing Challenges

2016-05-03 – Issam Raïs

Title: Towards Green Exascale Computing Challenges

Speaker: Issam Raïs

Abstract: Exascale is coming. Massively heterogeneous machines with hundreds of thousands of computing nodes and each of these nodes possessing hundreds of cores, bounded to each other by a dedicated and efficient network. On every component composing such a machine, we can spot many techniques to reduce energy consumption while maintaining good computing power. In such a context, this presentation aims at presenting the problematics being tackled in the current thesis.

PDF: presentation

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WG Hadrien Croubois: Toward an autonomic approach of workflows distribution on cloud

2016-04-19 Hadrien Croubois

Title: Toward an autonomic approach of workflows distribution on cloud ;

Speaker: Hadrien Croubois

Abstract: Advances in distributed systems technologies require a constant rethinking of previous deployments methods. Development of the Cloud paradigm is symptomatic of a broader tendency toward more dynamicity in the management of tasks and resources. However, the scientific computing still mostly uses old paradigms when deploying complex workflows. Our focus is therefore to propose a solution that will make the link between the needs of user in terms of scientific computation and the features offered by cloud providers. After having modelled both those needs and features, we describe the different mechanisms which are part of what should allow for an autonomous platform dedicated to collaborative scientific computing.

PDF: slides

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WG Issam Raïs: An analysis of the feasibility of energy harvesting with thermoelectric generators on petascale and exascale systems

2016-04-16 Issam Raïs

Title: An analysis of the feasibility of energy harvesting with thermoelectric generators on petascale and exascale systems;

Speaker: Issam Raïs

Abstract: The heat induced by computing resources is generally a waste of energy in supercomputers. This is especially true in very large scale supercomputers, where the produced heat has to be compensated with expensive and energy consuming cooling systems. An analysis of the feasibility of energy harvesting with thermoelectric generators on petascale and exascale systems; Energy is a critical point for future supercomputing trends that currently try to achieve exascale, without having its energy consumption reaching an important fraction of a nuclear power plant. Thus, new ways of generating or recovering energy have to be explored. Energy harvesting consists in recovering wasted energy. ThermoElectric Generators (TEGs) aim to recover energy by converting wasted dissipated energy into usable electricity. By combining computing units (CU) and TEGs at very large scale, we spotted a potential way to recover energy from wasted heat generated by computations on supercomputers. In this paper, we study the potential gains in combining TEGs with computational units at petascale and exascale. We present the technology behind TEGs, the study of a typical supercomputer environment, and finally our results concerning binding TEGs and computational units in a petascale and exascale system. With the available technology, we demonstrate that the use of TEGs in a supercomputer environment could be realistic and quickly profitable, and hence have a positive environmental impact.

PDF: Thermoelectricity

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WG Romaric Guilier: E-Biothon

2016-03-29 Romaric Guillier

Title: E-Biothon

Speaker: Romaric Guillier. 

Abstract: an experimental platform for BioInformatics; Abstract: The E-Biothon platform is an experimental Cloud platform to help speed up and advance research in biology, health and environment. It is based on a Blue Gene/P system and a web portal that allow members of the bioinformatics community to easily launch their scientific applications. This presentation describes the technical capacities of the platform, the different applications supported and finally a set of user experiences on the platform.

PDF: ebiothon_presentation_avalon

 

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Hadrien Croubois : Detecting Silent Data Corruption Using an Auxiliary Method and External Observer

Title: Detecting Silent Data Corruption Using an Auxiliary Method and External Observer

Speaker: Hadrien Croubois

Abstract: HPC platforms and application are becoming increasingly complex. Consequently, protecting results against all forms of corruption and ensuring trustworthiness are becoming more important. While previous work focuses on application-specific detectors, the dataflow manager in our current work in the Decaf project aims to have an efficient generic mechanism. We address those issues using new replication patterns that rely on the use of an auxiliary method and an external learning observer. In this talk, we present both the theoretical validation mechanisms and different use cases where our mechanism can be applied to detect silent data corruption.

2015-09-08_Hadrien

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Sonia Ben Mokhtar : Building Selfish-Resilient Distributed Systems

Title : Building Selfish-Resilient Distributed Systems

Speaker: Sonia Ben Mokhtar

Abstract: Collaborative systems (e.g., peer-to-peer instant messaging, file sharing, live streaming applications) generate among the largest amounts of traffic of today’s Internet. Common to all these systems is the assumption that, in return to the service offered by the collaborative system, users are willing to participate by sharing their resources with others. However, in practice, these systems suffer from selfish users that strategically free-ride the system whenever it is convenient for them. Albeit a number of solutions have been devised in the literature to deal with this problem, most of them are tailored to specific systems and thus lack flexibility and re-usability. During this seminar I will discuss methods for building selfish resilient distributed systems and future directions towards the automatic transformation of a given collaborative system into a system resilient to selfish behaviors.

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Sara Bouchenak : Service Level Agreement for Cloud Computing: Towards a Control-Theoretic Approach

Title : Service Level Agreement for Cloud Computing: Towards a Control-Theoretic Approach

Speaker: Sara Bouchenak

Abstract: Cloud Computing is a paradigm for enabling remote, on-demand access to a set of configurable computing resources. This model aims to provide hardware and software services to customers, while minimizing human efforts in terms of service installation, configuration and maintenance, for both cloud provider and cloud customer. A cloud may have the form of an Infrastructure as a Service (IaaS), a Platform as a Service (PaaS) or a Software as a Service (SaaS). However, cloud’s ad-hoc management in terms of quality-of-service and service level agreement (SLA) poses significant challenges to the performance, availability, energy consumption and economical costs of the cloud. We believe that a differentiating element between Cloud Computing environments will be the quality-of-service and the service level agreement (SLA) provided by the cloud. In this talk, we will discuss the definition and implementation of a novel cloud model: SLAaaS (SLA aware Service). The SLAaaS model enriches the general paradigm of Cloud Computing, and enables systematic and transparent integration of service levels and SLA to the cloud. SLAaaS is orthogonal to IaaS, PaaS and SaaS clouds and may apply to any of them. Both the cloud provider and cloud customer points of view are taken into account. From cloud provider’s point of view, we present autonomic SLA management to handle performance, availability, energy and cost issues in the cloud. An innovative approach combines control theory techniques with distributed algorithms and language support in order to build autonomic elastic clouds. Novel models, control laws, distributed algorithms and languages will be proposed for automated provisioning, configuration and deployment of cloud services to meet SLA requirements, while tackling scalability and dynamics issues. On the other hand from cloud customer’s point of view, we discuss SLA governance. It allows cloud customers to be part of the loop and to ba automatically notified about the state of the cloud, such as SLA violation and cloud energy consumption. The former provides more transparecy about SLA guaranties, and the latter aims to raise customers’ awareness about cloud’s energy footprint.

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Frédéric Prost : Category Theory 101, Graph Transformation and Social Data anonymisation.

Title : Category Theory 101, Graph Transformation and Social Data anonymisation.

Speaker: Frédéric Prost

Abstract: We will briefly introduce the basics of category theory in order to have a self-contained talk on Graph Transformation and an application to social data anonymisation. We will present the research field of social data anonymization: Huge network data sets, like social networks (describing personal relationships and cultural preferences) or communication networks (the graph of phone calls or email correspondents) become more and more common. These data sets are analyzed in many ways varying from the study of disease transmission to targeted advertising. Selling network data set to third-parties is a significant part of the business model of major internet companies. Usually, in order to preserve the confidentiality of the sold data set, only “anonymized” data are released: the original social networks is modified in order to avoid re-identification. The aim is to anonymize the data while keeping its use for the analyzes. We will review the most important results in this field, and we will show how graph rewriting techniques based on category theory can be used to design a more formal approach to tackle these issues.

2015-06-18-Prost