http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53292
--- Comment #2 from FH <fh_p at hotmail dot com> 2012-05-09 10:16:52 UTC --- I have just tested on another computer (CPU : Xeon5650 12 cores + OS : Scientific Linux) => I reproduce the unexpected behavior (OpenMP slower than single-threaded). So, I believe the problem is "rather" related to gcc (than to the OS) When I use more threads (export OMP_NUM_THREADS=2, then 6, then 12), OpenMP is "more slower" than single-threaded. (behavior related to thread initialisation ?)
