Français Anglais
Accueil Annuaire Plan du site
Home > Research results > Dissertations & habilitations
Research results
Ph.D de

Ph.D
Group : Parallel Systems

Méthodes de préconditionnement pour la résolution de systèmes linéaires sur des machines massivement parallèles

Starts on 10/09/2010
Advisor : GRIGORI, Laura
[GRIGORI Laura]

Funding :
Affiliation : Université Paris-Sud
Laboratory : LRI Grand Large

Defended on 10/04/2014, committee :
Directeur de la thèse
Laura Grigori, Directeur de Recherche, INRIA Rocquencourt

Rapporteurs
Olaf Schenk, Professeur, Institute of Computational Science, Universita della Svizzera italiana
Serge Gratton, Professeur, INPT/ENSEEIHT

Examinateurs
Pascal Henon, Ingenieur de recherche, Total
Yannis Manoussakis, Professeur, Paris 11, LRI
Frederic Nataf, Directeur de Recherche, CNRS Paris 6, Laboratoire J.L. Lions

Research activities :

Abstract :
This thesis addresses a new class of preconditioners which aims at accelerating solving large sparse systems arising in scientific and engineering problem by using preconditioned iterative methods. To apply these preconditioners, the input matrix needs to be reordered with K-way nested dissection. We also introduce an overlapping technique that adapts the idea of overlapping subdomains from domain decomposition methods to nested dissection based methods to improve the convergence of these preconditioners. Results show that such overlapping technique improves the convergence rate of Nested SSOR (NSSOR) and Nested Modified Incomplete LU with Rowsum property (NMILUR) precondtioners that we worked on. We also present the data distribution and parallel algorithms for implementing these preconditioners. Results show that on a 400x400x400 regular grid, the number of iterations with Nested Filtering Factorization preconditioner (NFF) increases slightly while increasing the number of subdomains up to 2048. In terms of runtime performance on Curie supercomputer, it scales up to 2048 cores and it is 2.6 times faster than the domain decomposition preconditioner Restricted Additive Schwarz (RAS) as implemented in PETSc.

Ph.D. dissertations & Faculty habilitations
APPRENTISSAGE ET OPTIMISATION SUR LES GRAPHES


ANALYSE DE DONNéES MULTI-MODALES POUR LES PATHOLOGIES COMPLEXES PAR LA CONCEPTION ET L’IMPLéMENTATION DE PROTOCOLES REPRODUCTIBLES ET RéUTILISABLES


DESIGNING INTERACTIVE TOOLS FOR CREATORS AND CREATIVE WORK
Creative work has been at the core of research in Human-Computer Interaction (HCI). I describe the results of a series of studies that look at how creators work, where creators include artists with years of professional practice, as well as learners, or novices and casual makers. My research focuses on three creation activities: drawing, physical modeling, and music composition. For these activities, I examine how artists switch between representations and how these representations evolve throughout their creative process, from early sketches to fine-grained forms or structured vocabularies. I present interactive systems that enrich their workflow (i) by extending their computer tools with physical user interfaces, or (ii) by making physical materials interactive. I also argue that sketch-based representations can allow for user interfaces that are more personal and less rigid. My presentation will reflect on lessons and limitations of this work and discuss challenges for future design-support tools.