1. a INRIA, Projet Tropics, BP 93 , 06902 , Sophia-Antipolis cedex, France
2. b Dept of Mechanical Engineering and Institute for Computational and Mathematical Engineering , Stanford University , Building 500, Stanford , CA , 94305-3035 , USA
3. c Mathématiques , université de Montpellier II , CC.051 34095 , Montpellier , France
4. d CASE Dpt. Barcelona Supercomputing Center BSC-CNS C/ Gran Capitán 2 2a Planta , 08034 , Barcelona , Spain