1. Department of Computational and Applied Mathematics Rice University 6100 Main MS‐134 Houston TX 77005 USA
2. Department of Mathematics Texas A&M University 3368 TAMU, College Station TX 77843‐3368 USA
3. LIMSI, CNRS Univ. Paris‐Sud, Université Paris‐Saclay Bât 508, rue John von Neumann, Campus Universitaire F‐91405 Orsay France