CERFACS CERFACS Scientific Activity Report Jan. 2010 – Dec. 2011

PARALLEL ALGORITHMS PROJECT
successfully solved. We also mention the availability of a software tool for testing optimization algorithms
that is described in Section 7.5 and that offers a lot of statistics for comparing optimization softwares. An
important feature of the team is the constant involvement in applications that is illustrated in most of the precited
research topics, but which appears also clearly in Sections 7.3, 7.4, 7.6 and 7.23, where applications
in electromagnetics, acoustics, aerodynamics have been tackled.
We continued our involvement into a large grant from RTRA-STAE to look into data assimilation
problems in conjunction with colleagues in CNES, ENSEEIHT-IRIT and Météo-France. This project,
named ADTAO, started in the spring of 2009 and will continue until 2012. We are involved in a study of
solution techniques for linear least-squares computations that lie at the heart of data assimilation algorithms,
and we have investigated several aspects of this including further studies on Gauss-Newton methods and
model reduction techniques. The fruitful collaboration with the foundation will continue even after year
2012, since the team has been given the responsibility to coordinate research on stochastic algorithms for
Data assimilation in the framework of the MoMa group of discussion. This group is expected to select
projects to be supported by the foundation in the area of complex physical systems.
The Parallel Algorithms Project is heavily involved in the Advanced Training aspects of CERFACS’
mission. We ran internal training courses for new recruits to all Projects at CERFACS to give them a
basic understanding of high performance computing and numerical libraries. This course was open to
the shareholders of CERFACS. We are involved in training through the “stagiaire” system and feel that
this is extremely useful to young scientists and engineers in both their training and their career choice.
In this reporting period, we had two stagiaires (Mohamed Biari and Youssef Diouane) from ENSEEIHT.
Members of the Team have assisted in many lecture courses at other centres, including Ecole Nationale de la
Météorologie, ENSEEIHT, ENSICA-ISAE, INSA and the University of Toulouse 1. Xavier Pinel defended
his thesis on preconditioned iterative methods for the Helmholtz problem in May 2010. Anke Tröltzsch
completed her PhD thesis on active set techniques for bound constrained derivative free optimization in
June 2011.
Our list of visitors is a veritable who’s who of numerical analysts, including many distinguished scientists
from Europe and the United States. We have included a list of the visitors at the end of this introduction.
In addition to inviting our visitors to give seminars, some of which are of general interest to other teams,
we also run a series of “internal seminars” that are primarily for Team members to learn about each other’s
work and are also a good forum for young researchers to hone their presentational skills.
We continue to have a “Sparse Days at CERFACS” meeting each year. On 15-17 June 2010, and 6-7
September 2011, these meeting were held with particular emphasis on sparse direct methods for the first
and high-performance computing for the second. The 2010 Sparse Days included the final workshop of the
ANR SOLSTICE project around direct methods for sparse matrices.
I am very pleased to record that, over the reporting period, we have continued our involvement in joint
research projects with shareholders and with other teams at CERFACS.
We have continued the collaboration with Airbus on shape optimization for drag minimization under lift
constraints (topic of the PhD thesis of Anke Tröltzsch). This is a challenging area since both the cost
function and the gradient are noisy, and because heavy CFD computations with the elsA code are involved.
Meta-model based optimization with noisy data and derivative free optimization algorithms have been
studied in this context. Related research on algorithms for aerodynamic shape optimization have also been
investigated in the framework of a DTP optimization project. This has been done in strong collaboration
with the CFD team (Aerodynamics group) at CERFACS and both EADS and ONERA.
We have continued to support CNES on gravity field determination. Our work is part of the RTRA-STAE
ADTAO project and concerns regularization techniques for solving inverse problems using observations
from the GRACE satellite.
CERFACS ACTIVITY REPORT 5