New submission from Antoine Pitrou <pit...@free.fr>: Currently, Python produces hash values with fit in a C "long". This is fine at first sight, but in the context of dict and set implementations, it means that 1) holding hashes and indices in the same field of a structure requires some care (see issue1646068) 2) on platforms where a long is smaller than a Py_ssize_t (e.g. Win64), very big hash tables could suffer from lots of artificial collisions (the hash table being bigger than the range of possible hash values) 3) when a long is smaller than Py_ssize_t, we don't save any size anyway, since having some pointers follow a C "long" in a structure implies some padding to keep all fields naturally aligned
A future-proof option would be to change all hash values to be of Py_ssize_t values rather than C longs. Either directly, or by defining a new dedicated alias Py_hash_t. This would also impact the ABI, I suppose. ---------- components: Interpreter Core messages: 115617 nosy: belopolsky, georg.brandl, jimjjewett, ked-tao, loewis, mark.dickinson, pitrou, rhettinger, tim_one priority: normal severity: normal status: open title: Make hash values the same width as a pointer (or Py_ssize_t) type: feature request versions: Python 3.2, Python 3.3 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue9778> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
