Sylvain Pion

Research

I am 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

• A Generic Lazy Evaluation Scheme for Exact Geometric Computations
  S. Pion and A. Fabri. Science of Computer Programming, 2011.
  
• Parallel Geometric Algorithms for Multi-Core Computers
  V. H. F. Batista, D. L. Millman, S. Pion and J. Singler. CGTA, 2010.
• Directed Rounding Arithmetic Operations in C++
  G. Melquiond and S. Pion. ISO, WG21 document number N2811, 2008.
• Robust construction of the three-dimensional flow complex
  F. Cazals, A. Parameswaran and S. Pion. SoCG, 2008.
• FPG: A code generator for fast and certified geometric predicates
  A. Meyer and S. Pion. RNC, 2008.
• Classroom Examples of Robustness Problems in Geometric Computations
  L. Kettner, K. Mehlhorn, S. Pion, S. Schirra and C. Yap. CGTA, 2008.

Collaborative projects

• ANR Galapagos : formal proofs of geometric algorithms.
• ANR Triangles : advances around triangulations (moving points, more spaces, parallel algorithms...).
• Past ones : GENEPI (associated team I managed), ANR Geotopal, AIM@SHAPE, ACS, ECG, FIABLE, GALIA, CGAL.

Standardization

• 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

• 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 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).