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Tom Cornebize

Mercredi 2 juin 2021

Calcul haute performance : vers de meilleures prédictions de performance et expériences


The scientific community relies more and more on computations, notably for numerical simulation and data processing.  While many scientific advances were made possible by the technological progress of computers, additional performance gains are still required for larger scale projects.

The race for performance is addressed with a growing hardware and software complexity, which in turn increases the performance variability. This can make the experimental study of performance extremely challenging, raising concerns of reproducibility of the experiments, akin to the problems already faced by natural sciences.

Our contributions are twofold. First, we present a methodology for predicting the performance of parallel non-trivial applications through simulation. We describe several models for communications and computations, with an increasing complexity. We compare these models through an extensive validation by matching our predictions with real experiments.  This validation shows that modeling the spatial and temporal variability of the platform is essential for faithful predictions. As a consequence, predictions require careful sensibility analysis accounting for the uncertainty on the resource models, which we illustrate through several case studies.  Second, we present the lessons learned while making the numerous experiments required in the first part and how we improved our methodology. We show that measurements can suffer from multiple experimental biases and we explain how some of these biases can be overcome. We also present how we implemented systematic performance non-regression testing, which allowed us to detect many significant changes of the platform throughout this thesis.

Date et Lieu

Mercredi 2 juin à 16h00

Organisé par


Composition du Jury

CEA (France), rapporteur
University of Hawai'i at Mānoa (États-Unis), rapporteur
University of Maryland (États-Unis), examinateur
Camille COTI
Université Sorbonne Paris Nord (France), examinatrice
Télécom SudParis (France), examinatrice
Jean-François MEHAUT
Université Grenoble Alpes (France), examinateur
Christian PLESSL
Universität Paderborn (Allemagne), examinateur
CNRS (France), directeur de thèse

Publié le 20 mai 2021

Mis à jour le 20 mai 2021