Events in March–April 2018
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February 26, 2018
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February 27, 2018
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February 28, 2018
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MarchMarch 1, 2018(1 event)KeynoteKeynote N/A |
March 2, 2018
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March 5, 2018
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March 6, 2018
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March 7, 2018
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March 8, 2018(1 event)
Randomized Load Balancing: Asymptotic Optimality of Power-of-d-Choices with Memory by Jonatha Anselmi (Inria Bordeaux)Randomized Load Balancing: Asymptotic Optimality of Power-of-d-Choices with Memory by Jonatha Anselmi (Inria Bordeaux) – In multi-server distributed queueing systems, the access of stochastically arriving jobs to resources is often regulated by a dispatcher. A fundamental problem consists in designing a load balancing algorithm that minimizes the delays experienced by jobs. During the last two decades, the power-of-d-choice algorithm, based on the idea of dispatching each job to the least loaded server out of $d$ servers randomly sampled at the arrival of the job itself, has emerged as a breakthrough in the foundations of this area due to its versatility and appealing asymptotic properties. We consider the power-of-d-choice algorithm with the addition of a local memory that keeps track of the latest observations collected over time on the sampled servers. Then, each job is sent to a server with the lowest observation. We show that this algorithm is asymptotically optimal in the sense that the load balancer can always assign each job to an idle server in the large-server limit. This holds true if and only if the system load $\lambda$ is less than $1-\frac{1}{d}$. If this condition is not satisfied, we show that queue lengths are bounded by $j^\star+1$, where $j^\star\in\mathbb{N}$ is given by the solution of a polynomial equation. This is in contrast with the classic version of the power-of-d-choice algorithm, where queue lengths are unbounded. Our upper bound on the size of the most loaded server, $j^*+1$, is tight and increases slowly when $\lambda$ approaches its critical value from below. For instance, when $\lambda= 0.995$ and $d=2$ (respectively, $d=3$), we find that no server will contain more than just $5$ ($3$) jobs in equilibrium. Our results quantify and highlight the importance of using memory as a means to enhance performance in randomized load balancing. |
March 9, 2018
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March 11, 2018
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March 13, 2018
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March 14, 2018
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March 15, 2018(1 event)
Obtaining Dynamic Scheduling Policies with Simulation and Machine Learning (by Danilo Santos, Datamove)Obtaining Dynamic Scheduling Policies with Simulation and Machine Learning (by Danilo Santos, Datamove) – Obtaining Dynamic Scheduling Policies with Simulation and Machine Learning Abstract: Dynamic scheduling of tasks in large-scale HPC platforms is normally accomplished using ad-hoc heuristics, based on task characteristics, combined with some backfilling strategy. Defining heuristics that work efficiently in different scenarios is a difficult task, specially when considering the large variety of task types and platform architectures. In this work, we present a methodology based on simulation and machine learning to obtain dynamic scheduling policies. Using simulations and a workload generation model, we can determine the characteristics of tasks that lead to a reduction in the mean slowdown of tasks in an execution queue. Modeling these characteristics using a nonlinear function and applying this function to select the next task to execute in a queue improved the mean task slowdown in synthetic workloads. When applied to real workload traces from highly different machines, these functions still resulted in performance improvements, attesting the generalization capability of the obtained heuristics. |
March 16, 2018
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March 18, 2018
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March 19, 2018
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March 20, 2018
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March 21, 2018
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March 22, 2018(1 event)
A Class of Stochastic Multilayer Networks: Percolation, Exact and Asymptotic Results by Philippe Nain (inria, Lyon)A Class of Stochastic Multilayer Networks: Percolation, Exact and Asymptotic Results by Philippe Nain (inria, Lyon) – Abstract: Bâtiment IMAG (442) |
March 23, 2018
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March 24, 2018
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March 25, 2018
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March 26, 2018
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March 27, 2018
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March 28, 2018(1 event)
Parallel Space-Time Kernel Density Estimation By Erik Saule (U. Caroline du Nord)Parallel Space-Time Kernel Density Estimation By Erik Saule (U. Caroline du Nord) – The exponential growth of available data has increased the need for We focus in this paper on events that are localized among three Bâtiment IMAG (442) |
March 29, 2018(1 event)
Polyhedral Optimization at Runtime, by Manuel Selva.Polyhedral Optimization at Runtime, by Manuel Selva. – The polyhedral model has proven to be very useful to optimize and parallelize a particular class of compute intensive application kernels. A polyhedral optimizer needs to have affine functions defining loop bounds, memory accesses and branching conditions. Unfortunately, this information is not always available at compile time. To broaden the scope of polyhedral optimization opportunities, runtime information can be considered. This talk will highlight the challenges of integrating polyhedral optimization in runtime systems: - When and how to detect opportunities for polyhedral optimization? These challenges will be illustrated in the context of both the APOLLO framework targeting C and C++ applications and of the JavaScript engine from Apple. Bâtiment IMAG (442) |
March 30, 2018
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March 31, 2018
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AprilApril 1, 2018 |
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April 9, 2018
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April 10, 2018
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April 11, 2018
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April 12, 2018(1 event)
presentation of the Argo project by Swann Perarnau (Argonne National Laboratory)presentation of the Argo project by Swann Perarnau (Argonne National Laboratory) – |
April 13, 2018
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April 15, 2018
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April 23, 2018
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April 24, 2018
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April 25, 2018
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April 26, 2018(1 event)
Approximate equilibria of Colonel Blotto games, by Quan Vu (Polaris and Nokia)Approximate equilibria of Colonel Blotto games, by Quan Vu (Polaris and Nokia) – Resource allocation games are commonly used to model problems in many domains ranging from security to advertising. One of the most important resource allocation games is the Colonel Blotto game: Two players distribute a fixed budget of resources over multiple battlefields to maximize the aggregate value of battlefields they win, each battlefield being won by the player who allocates more resources to it. Despite its long-standing history and importance, the continuous version of the game---where players can choose any fractional allocation---still lacks a complete Nash equilibrium solution in its general form with asymmetric players' budgets and heterogeneous battlefield values. In this work, we propose an approximate equilibrium for this general case. We construct a simple strategy (the independently uniform strategy) and prove that it is an epsilon-equilibrium. We give a theoretical bound on the approximation error in terms of the number of battlefields and players’ budgets which identifies precisely the parameters regime for which our strategy is a good approximation. We also investigate an extension to the discrete version (where players can only have integer allocations), for which we proposed an algorithm to compute very efficiently an approximate equilibrium. We perform numerical experiments that guarantee that we can "safely" use this strategy in practice. Our work extends the scope of application of Colonel Blotto games in several practical cases, especially with large games' parameters (e.g. in advertisements, voting, security, etc.,) Bâtiment IMAG Saint-Martin-d'Hères, 38400 France |
April 27, 2018
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April 28, 2018
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April 29, 2018
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April 30, 2018
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MayMay 1, 2018 |
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May 4, 2018(1 event)
A data structure for analyzing spatio-temporal correlations of alarms, by Anne Bouillard (Nokia)A data structure for analyzing spatio-temporal correlations of alarms, by Anne Bouillard (Nokia) – In this talk, I will present a data structure for the analysis of correlations of alarms, for root-cause analysis or prediction purposes. This is a joint work with Marc-Olivier Buob and Maxime Raynal (intern). A sequence of alarms is modeled by a directed acyclic graph. The nodes of the graph are the alarms, that are represented by a symbol and an interval of time. An arc of the graph is interpreted as a potential causality between two alarms. I will first show how to build a "compact" structure storing all the potential causal sequences of alarms and then how to weight this structure so that the actual correlations can be detected. The efficiency of the approach will be demonstrated on toy examples. Bâtiment IMAG (442) |
May 5, 2018
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May 6, 2018
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