Events in March–April 2022
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February 28, 2022
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MarchMarch 1, 2022 |
March 2, 2022
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March 3, 2022(1 event) Polaris-tt: Chen Yan: restless bandits and LP-relaxations – |
March 4, 2022
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March 5, 2022
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March 6, 2022
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March 7, 2022
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March 8, 2022
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March 9, 2022
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March 10, 2022(1 event) Polaris-tt: Kimang Khun: computing index policies for restless bandits – |
March 11, 2022
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March 12, 2022
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March 13, 2022
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March 14, 2022
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March 15, 2022
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March 16, 2022
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March 17, 2022(2 events) Polaris-tt: Till Kletti (Introducing the expohedron for fair and useful rankings) – Based on https://dl.acm.org/doi/10.1145/3488560.3498490 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, |
March 18, 2022
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March 19, 2022
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March 20, 2022
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March 21, 2022
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March 22, 2022
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March 23, 2022
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March 24, 2022(2 events) 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. |
March 25, 2022
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March 26, 2022
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March 27, 2022
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March 28, 2022
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March 29, 2022
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March 30, 2022
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March 31, 2022(1 event) 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. |
AprilApril 1, 2022 |
April 2, 2022
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April 3, 2022
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April 4, 2022
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April 5, 2022
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April 6, 2022
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April 7, 2022(1 event) Polaris-tt: Achile Baucher: le modèle World3 – |
April 8, 2022
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April 9, 2022
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April 10, 2022
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April 11, 2022
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April 12, 2022
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April 13, 2022
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April 14, 2022(1 event) Polaris-tt: Rémi Castera - Statistical discrimination in Stable Matchings – |
April 15, 2022
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April 16, 2022
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April 17, 2022
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April 18, 2022
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April 19, 2022
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April 20, 2022
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April 21, 2022
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April 22, 2022
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April 23, 2022
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April 24, 2022
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April 25, 2022
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April 26, 2022
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April 27, 2022
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April 28, 2022(2 events) 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 |
April 29, 2022
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April 30, 2022
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MayMay 1, 2022 |