Marc-Andre Lemburg <m...@egenix.com> added the comment: > To see the collision counting, enable the DEBUG_DICT_COLLISIONS > macro variable.
Running (part of (*)) the test suite with debugging enabled on a 64-bit machine shows that slot collisions are much more frequent than hash collisions, which only account for less than 0.01% of all collisions. It also shows that slot collisions in the low 1-10 range are most frequent, with very few instances of a dict lookup reaching 20 slot collisions (less than 0.0002% of all collisions). The great number of cases with 1 or 2 slot collisions surprised me. It seems that there's potential for improvement of the perturbation formula left. Due to the large number of 1 or 2 slot collisions, the patch is going to cause a minor hit to dict lookup performance. It may make sense to unroll the slot search loop and only start counting after the third round of misses. (*) I stopped the run after several hours run-time, producing some 148GB log data. ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue13703> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
