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October 20, 2022
Titre : Possible interactions between task-based runtime systems and communication libraries
Abstract :
The increasing complexity of supercomputers leads to the emergence of task-based runtime systems, to exploit more easily the performance they can offer. These runtime systems usually rely on a third-party library to perform communications (following the MPI standard, for instance) when they are used in a distributed fashion. In this presentation, I will summarize my work during my PhD about possible interactions between task-based runtime systems and communication libraries. The interactions can be positive, for instance improving the performance by detecting and executing broadcasts in a smart way; or negative and hurting the application performance, for instance because of contention between communications and computations. I will also mention some results regarding the tracing system used to analyze executions: the sources of overhead and the problem of accurate clock synchronization.
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26September 26, 2022
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28September 28, 2022
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30September 30, 2022
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October1October 1, 2022 |
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3October 3, 2022
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4October 4, 2022
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5October 5, 2022
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7October 7, 2022
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8October 8, 2022
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9October 9, 2022
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10October 10, 2022
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11October 11, 2022
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Seminar Joao Comba: Data Visualization for The Understanding of COVID-19 – Title: Data Visualization for The Understanding of COVID-19 Bâtiment IMAG (442) |
Séminaire Antoine Oustry: Polynomial optimization for parameterizing dynamical systems – Polynomial optimization for parameterizing dynamical systems Abstract: We consider a polynomial dynamical system that depends on some tunable parameters. We raise the question of how to configure this system optimally, in terms of costs and stability. |
14October 14, 2022
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15October 15, 2022
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16October 16, 2022
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17October 17, 2022
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18October 18, 2022
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19October 19, 2022
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Séminaire Philippe Swartvagher (Inria Bordeaux): Possible interactions between task-based runtime systems and communication libraries – Titre : Possible interactions between task-based runtime systems and communication libraries Abstract : The increasing complexity of supercomputers leads to the emergence of task-based runtime systems, to exploit more easily the performance they can offer. These runtime systems usually rely on a third-party library to perform communications (following the MPI standard, for instance) when they are used in a distributed fashion. In this presentation, I will summarize my work during my PhD about possible interactions between task-based runtime systems and communication libraries. The interactions can be positive, for instance improving the performance by detecting and executing broadcasts in a smart way; or negative and hurting the application performance, for instance because of contention between communications and computations. I will also mention some results regarding the tracing system used to analyze executions: the sources of overhead and the problem of accurate clock synchronization. |
21October 21, 2022
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22October 22, 2022
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23October 23, 2022
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24October 24, 2022
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25October 25, 2022
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26October 26, 2022
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Seminar Bryce Ferguson: "Information and Influence: Overcoming and Exploiting Uncertainty in Congestion Games" – Bryce Ferguson (https://web.ece.ucsb.edu/~blf/)
Title: Information and Influence: Overcoming and Exploiting Uncertainty in Congestion Games
Abstract: In large-scale, socio-technical systems (such as traffic networks, power grids, supply chains, etc.) the operating efficiency depends heavily on the actions of human users. It is well known that when users act in their own self-interest, system performance can be sub-optimal. Our capabilities in alleviating this inefficiency rely on our knowledge of user decision making and various system parameters. In this talk, I will present two settings where information affects our ability to influence system performance. In the first, we consider designing monetary incentives for players in a congestion game without exact knowledge of users’ price-sensitivity or path latency-characteristics; we provide a comparison of the effectiveness of different incentive types and quantify the value of different pieces of information. In the second, we consider a flipped paradigm, where the system operator has more information about system parameters than the users and can selectively reveal pertinent information. We show, in the context of Bayesian-congestion games, that signaling information to users has the opportunity to improve system performance but also the capability to make performance worse than if no information were shared at all. We then show the advantages of concurrently using monetary incentives and information signals by providing bounds on the benefit to system performance and methods to find optimal mechanisms of each type.
Bâtiment IMAG (406) Saint-Martin-d'Hères, 38400 France |
28October 28, 2022
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29October 29, 2022
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30October 30, 2022
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31October 31, 2022
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November1November 1, 2022 |
2November 2, 2022
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3November 3, 2022
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4November 4, 2022
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5November 5, 2022
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6November 6, 2022
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7November 7, 2022
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8November 8, 2022
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9November 9, 2022
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Verimag seminar: Stephan Plassart – Total Flow Analysis (TFA) is a method for conducting the worst-case analysis of time sensitive networks without cyclic dependencies. In networks with cyclic dependencies, Fixed-Point TFA introduces artificial cuts, analyses the resulting cycle-free network with TFA, and iterates. If it converges, it does provide valid performance bounds. We show that the choice of the specific cuts used by Fixed-Point TFA does not affect its convergence nor the obtained performance bounds, and that it can be replaced by an alternative algorithm that does not use any cut at all, while still applying to cyclic dependencies. Room: 206 Bâtiment IMAG (206) |
11November 11, 2022
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12November 12, 2022
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13November 13, 2022
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14November 14, 2022
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15November 15, 2022
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16November 16, 2022
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Seminar Olivier Bilenne – Solutions of Poisson's equation for first-policy improvement in parallel queueing systems
This talk addresses the problem of (state-aware) job dispatching at minimum long-run average cost in a parallel queueing system with Poisson arrivals. Policy iteration is a technique for approaching optimality through improvement of an initial dispatching policy. Its implementation rests on the computation of value functions. In this context, we will consider the M/G/1-FCFS queue endowed with an arbitrary cost function for the waiting times of the incoming jobs. The associated relative value function is a solution of Poisson's equation for Markov chains, which I propose to solve in the Laplace transform domain by considering an ancillary stochastic process extended to (imaginary) negative backlog states. This construction enables us to issue closed-form solutions for simple cost functions (polynomial, exponential, and their piecewise compositions), in turn permitting the derivation of interval bounds for the relative value functions to more general cost functions. Such bounds allow for an exact implementation of the first improvement step of policy iteration in a parallel queueing system.
One objective of the talk is to identify the main obstacles to the implementation of the policy iteration algorithm in parallel queueing systems; the purpose then to discuss the new directions that transform domain analysis might offer beyond first policy improvement.
Further reading: Olivier Bilenne. Dispatching to parallel servers: solutions of Poisson's equation for first-policy improvement. Queueing Systems, Springer Verlag, 2021, Queueing Systems, 99 (3), pp.199-230. https://hal.archives-ouvertes.fr/hal-02925284
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18November 18, 2022
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19November 19, 2022
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20November 20, 2022
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21November 21, 2022
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22November 22, 2022
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23November 23, 2022
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24November 24, 2022
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25November 25, 2022
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26November 26, 2022
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27November 27, 2022
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28November 28, 2022
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29November 29, 2022
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30November 30, 2022
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December1December 1, 2022●(1 event)Séminaire Stephane Durand – Jeux de contagions et d'influences: les différentes formes, les approches et le contexte |
2December 2, 2022
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3December 3, 2022
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4December 4, 2022
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