Sylvain Pion

Formerly Research Scientist at INRIA Bordeaux Sud-Ouest

Research

I left INRIA in Dec. 2021, thus ending my research scientist career.
From Mar. 2020 to Dec. 2021, I was stand-alone researcher at INRIA Bordeaux
From Dec. 2017 to Feb. 2020, I was a member of the AUCTUS team at INRIA Bordeaux
From 2011 to 2017, I was on leave from INRIA, working as Software Engineer at Google and then Apple in California
From 2003 to 2010, I was Research Scientist in the Geometrica project-team at INRIA Sophia-Antipolis

I was interested in computer programming of geometric algorithms.

Mesh generation and the other algorithms developed by my co-workers from Geometrica are of particular interest, as well as any computational geometry algorithm you may find for example in CGAL.

Programming issues of interest are: the efficiency of basic certified numerical routines (the geometric predicates and constructions which are so critical to the robustness of geometric algorithms), formal proofs of algorithms, parallel algorithms and compact memory representations of data structures. I am also interested in compiler optimizations and programming languages, especially C++. Another important direction of programming is the maintainability of large code bases like CGAL, which triggers research on finding concepts with broad applicability to help code factorization and understandability, within the generic programming paradigm.

Publications and presentations

The list of all my publications on HAL-Inria, and on Google Scholar. Below are some of my recent publications and presentations.

My last paper should hopefully appear in 2022 in JoCG. "Improved polytope volume calculations based on Hamiltonian Monte Carlo with boundary reflections and sweet arithmetics", authored with Frédéric Cazals and Augustin Chevallier. Prepublication here.
The arithmetic toolbox in CGAL (with video), given at the Mini-workshop on iRRAM/MPFR/MPC in Dagstuhl, April 19, 2018.
La bibliothèque logicielle CGAL, Séminaire au Collège de France dans le cadre du cours « Géométrie algorithmique : données, modèles, programmes » de Jean-Daniel Boissonnat, 26 avril 2017.

Collaborative projects

Past ones : GENEPI (associated team I managed), ANR Galapagos, ANR Triangles, ANR Geotopal, AIM@SHAPE, ACS, ECG, FIABLE, GALIA, CGAL.

Standardization

In connection to my research, I participate to the work of the following standardization committees:

WG21 : the ISO working group for the standardization of the C++ programming language. Here is a list of my C++ work.
IEEE-1788 : standardization of interval arithmetic.

Software

Most of my developments are done around CGAL, of which I am a member of the editorial board (which I chaired from February 2006 to June 2010). Watch the general presentation video !

CGAL : I significantly contributed to:
- the 2D/3D triangulations,
- the geometric kernel,
- the arithmetic kernel (floating-point filters...),
- plenty of other stuff,
- the Python and Scilab bindings,
- the overall technical direction of the project through the CGAL editorial board,
- the maturation of key parts which allowed the creation of GeometryFactory in 2003, the company distributing CGAL, with which I am still frequently in contact.
Boost : I am a co-author of the Boost.Interval library.
CORE : I implemented improvements to the root bound mechanism for floating-point input, and other optimizations.
GCC : I implemented a few optimizations helping interval arithmetic (some expression transformations).
♕ N-queens problem : I used to hold the world record for N=21-23 using a distributed program.
Miscellaneous: the Linux kernel, where I once added support for large swap areas, and some other old programs.

Program committees and editorial responsibilities

Paper committee of ESA 2010 (Engineering and Applications Track).
Videos/multimedia program committee of SoCG 2009.
Paper committee of SoCG 2006.
Co-editor of a special issue of CGTA on Robust Geometric Algorithms and their Implementations in 2005.

Teaching

Some courses I gave.
Jury : I was member of the jury at the entrance examination of the ENS (algorithmic and programming oral exam), from 2007 to 2009.

Other responsibilities

I was a member of the CUMIR (IT systems users comittee) at INRIA Bordeaux 2017-2020
I was "responsable permanent" (sort of vice-head ?) in the AUCTUS team at INRIA Bordeaux 2017-2020
I was "secrétaire du comité des projets" in 2010
I was a member of the CDL, the local committee dealing with software development from 2004 to 2007.
Jean-Paul Rigault and I organized a WG21 Meeting in Sophia Antipolis, in June 2008.

Miscellaneous

What do I do in my free time ? I like gardening, paragliding/flying, rock-climbing, biking... See also some bike benchmarks.
Some old archives of the mailing-list std-interval (2006), now hosted here.
Some old information about the FFJM (French Federation of Mathematical and Logical games).