http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58756
--- Comment #3 from Uroš Bizjak <ubizjak at gmail dot com> --- Adding omp_get_thrad_num to the printf: $ ./a.out 3 496 3 496 2 496 2 496 2 496 2 496 2 496 2 496 2 496 2 496 3 496 3 496 3 496 3 496 3 496 3 496 1 496 1 496 1 496 1 496 1 496 1 496 0 496 0 496 0 496 0 496 0 496 0 496 0 496 0 496 1 496 1 496 tot 1984 Aborted So, the summing variable in the outer loop is not increased.