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Mar 7, '22March 7, 2022
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Mar 8, '22March 8, 2022
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Mar 9, '22March 9, 2022
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Mar 10, '22March 10, 2022●(1 event)
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Mar 11, '22March 11, 2022
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Mar 12, '22March 12, 2022
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Mar 13, '22March 13, 2022
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| MMonday | TTuesday | WWednesday | TThursday | FFriday | SSaturday | SSunday |
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28February 28, 2022
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March1March 1, 2022 |
2March 2, 2022
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Polaris-tt: Chen Yan: restless bandits and LP-relaxations – |
4March 4, 2022
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5March 5, 2022
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6March 6, 2022
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7March 7, 2022
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8March 8, 2022
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9March 9, 2022
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Polaris-tt: Kimang Khun: computing index policies for restless bandits – |
11March 11, 2022
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12March 12, 2022
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13March 13, 2022
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14March 14, 2022
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15March 15, 2022
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16March 16, 2022
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Polaris-tt: Till Kletti (Introducing the expohedron for fair and useful rankings)Seminar Bruno Raffin (Large Scale Data Assimilation) – Title: Large Scale Data Assimilation Authors: Sebastian Friedemann and Bruno Raffin Abstract: How to combine data, which may be available though different sensors, |
18March 18, 2022
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19March 19, 2022
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20March 20, 2022
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21March 21, 2022
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22March 22, 2022
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23March 23, 2022
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Polaris-tt: Victor Boone (title to be annouced) – Polaris-datamove seminar: Georges Da Costa (Multi-objective resources optimization Performance- and Energy-aware HPC and Clouds) – Titre: "Multi-objective resources optimization Performance- and Energy-aware HPC and Clouds" This talk will answer to the challenge "How to efficiently manage a datacenter ?" by providing theoretical and practical tools. Datacenters are at the center of the life of an increasing part of the world population while being mostly unknown: From online services to weather forcast. Their role, while transparent, is of the utmost importance. Their electricity consumption is then a key challenge, and will be even more in a near future. Managing efficiently leads to optimization of quality of service, but also to improving energy efficiency. This talk will show the required tools: The tools linked to measures and monitoring, from a technical point of view, but also by the definition of metrics. Then, it will explore methods to model such problems, along with direct or approximated resolution techniques. The next step will show several heuristics to quickly reach approximated solutions. Several types of validations, from experimental to improved simulated ones will serve as support for this talk. |
25March 25, 2022
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26March 26, 2022
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27March 27, 2022
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28March 28, 2022
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29March 29, 2022
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30March 30, 2022
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Seminar Bertrand Simon (An Exact Algorithm for the Linear Tape Scheduling Problem) – Title: An Exact Algorithm for the Linear Tape Scheduling Problem Abstract: Magnetic tapes are often considered as an outdated storage technology, yet they are still used to store huge amounts of data. Their main interests are a large capacity and a low price per gigabyte, which come at the cost of a much larger file access time than on disks. With tapes, finding the right ordering of multiple file accesses is thus key to performance. Moving the reading head back and forth along a kilometer long tape has a non-negligible cost and unnecessary movements thus have to be avoided. However, the optimization of tape request ordering has then rarely been studied in the scheduling literature, much less than I/O scheduling on disks. For instance, minimizing the average service time for several read requests on a linear tape remains an open question. Therefore, in this paper, we aim at improving the quality of service experienced by users of tape storage systems, and not only the peak performance of such systems. To this end, we propose a reasonable polynomial-time exact algorithm while this problem and simpler variants have been conjectured NP-hard. We also refine the proposed model by considering U-turn penalty costs accounting for inherent mechanical accelerations. Then, we propose a low-cost variant of our optimal algorithm by restricting the solution space, yet still yielding an accurate suboptimal solution. Finally, we compare our algorithms to existing solutions from the literature on logs of the mass storage management system of a major datacenter. This allows us to assess the quality of previous solutions and the improvement achieved by our low-cost algorithm. Aiming for reproducibility, we make available the complete implementation of the algorithms used in our evaluation, alongside the dataset of tape requests that is, to the best of our knowledge, the first of its kind to be publicly released. |
April1April 1, 2022 |
2April 2, 2022
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3April 3, 2022
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4April 4, 2022
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5April 5, 2022
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6April 6, 2022
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Polaris-tt: Achile Baucher: le modèle World3 – |
8April 8, 2022
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9April 9, 2022
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10April 10, 2022
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11April 11, 2022
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12April 12, 2022
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13April 13, 2022
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Polaris-tt: Rémi Castera - Statistical discrimination in Stable Matchings – |
15April 15, 2022
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16April 16, 2022
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17April 17, 2022
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18April 18, 2022
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19April 19, 2022
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20April 20, 2022
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21April 21, 2022
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22April 22, 2022
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23April 23, 2022
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24April 24, 2022
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25April 25, 2022
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26April 26, 2022
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27April 27, 2022
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Polaris-tt: Victor Leger – A large dimensional analysis of multi-task semi-supervised classification – Seminar by Martin Schreiber (LJK, Airsea) – Title: A Brief Glimpse on Emerging Time Integration Methods for Weather and Climate Simulations Speaker: Martin Schreiber Abstract: Weather and climate simulations face new challenges due to changes in computer architectures caused by physical limitations. From a pure computing perspective, algorithms are required to cope with stagnating or even decreasing per-core speed and increasing on-chip parallelism. These trends will continue and already led to research on partly disruptive mathematical and algorithmic reformulations of dynamic cores, e.g., using (additional) parallelism along the time dimension. This presentation provides an overview and introduction of a variety of promising newly developed and evaluated time integration methods for equations related to prototypical dynamical cores, all aimed at improving the ratio of wall clock time vs. error: Rational Approximation of Exponential Integration (REXI), Parallel Full Approximation Scheme in Space and Time (PFASST) and Semi-Lagrangian methods combined with Parareal. We get improved time-vs.-error rates, but sometimes with additional challenges on the way which needs to be further overcome. Overall, our results motivate further investigation and combination of these methods for operational weather/climate systems. I gratefully acknowledge collaborators related to this presentation |
29April 29, 2022
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30April 30, 2022
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May1May 1, 2022 |
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