Cerfacs Enter the world of high performance ...

The 1 June 2016 at 14h00

HABILITATION DEFENSE : Xavier VASSEUR – Contribution to the study of efficient iterative methods for the numerical solution of partial differential equations

Brigitte Yzel |  SALLE DE CONFERENCE JEAN-CLAUDE ANDRE |  

Multigrid and domain decomposition methods provide efficient algorithms for the numerical solution of partial differential equations arising in the modeling of many applications in Computational Science and Engineering. This manuscript covers certain aspects of modern iterative solution methods for the solution of large-scale problems issued from the discretization of partial differential equations. More specifically, we focus on geometric multigrid methods, non-overlapping substructuring methods and flexible Krylov subspace methods with a particular emphasis on their combination. First, the combination of multigrid and Krylov subspace methods is investigated on a linear partial differential equation modeling wave propagation in heterogeneous media. Secondly, we focus on non-overlapping domain decomposition methods for a specific finite element discretization known as the $hp$ finite element, where unrefinement/refinement is allowed both by decreasing/increasing the step size h or by decreasing/increasing the polynomial degree p of the approximation on each element. Results on condition number bounds for the domain decomposition preconditioned operators are given and illustrated by numerical results on academic problems in two and three dimensions. Thirdly, we review recent advances related to a class of Krylov subspace methods allowing variable preconditioning. We detail flexible Krylov subspace methods including augmentation and/or spectral deflation, where deflation aims at capturing approximate invariant subspace information. We also present flexible Krylov subspace methods for the solution of linear systems with multiple right-hand sides given simultaneously. The efficiency of the numerical methods is demonstrated on challenging applications in seismics requiring the solution of huge linear systems of equations with multiple right-hand sides on parallel distributed memory computers. Finally, we expose current and future prospectives towards the design of efficient algorithms on extreme scale machines for the solution of problems issued from the discretization of partial differential equations.

Jury :

Iain Duff                        – Examiner             (Rutherford Appleton Laboratory, UK and Cerfacs, France)

Andreas Frommer        – Referee                (University of Wuppertal, Germany)

Serge Gratton               – Examiner              (INPT-IRIT, France)

Frédéric Nataf              – Referee                (Université Pierre et Marie Curie, France)

Cornelis Oosterlee       – Referee                (CWI and TU Delft, The Netherlands)

Michel Visonneau        – Examiner              (Ecole Centrale de Nantes, France)

NEWS

Invited communication to the BIDS'17 conference

thual |  12 December 2017

During an invited communication to the « Big Data from Space 2017 » conference, CERFACS presented the stakes and the perspectives of its strategic axis "Data Driven Modeling" from the point of view of the valorization of satellite data. For more details, see the article:...Read more


One Cerfacs’ proposal accepted in PRACE 15th call

superadmin |  4 December 2017

This study focuses on Hall-effect thrusters, which were first invented in the 1960s. Although such systems have been extensively studied, the detailed physics of the magnetized plasmas in these thrusters is very complex and several plasma processes that have direct influence on the thruster...Read more

ALL NEWS