In: http://lists.llvm.org/pipermail/openmp-dev/2015-August/000858.html, a performance issue was found with libomp's task dependencies.
The task dependencies hash table has an issue with collisions. The current table size is a power of two. This combined with the current hash function causes a large number of collisions to occurr. Also, the current size (64) is too small for larger applications so the table size is increased.
This patch creates a two level hash table approach for task dependencies. The implicit task is considered the "master" or "top-level" task which has a large static sized hash table (997), and nested tasks will have smaller hash tables (97). Prime numbers were chosen to help reduce collisions.