Jim Jewett <jimjjew...@gmail.com> added the comment: On Thu, Jan 26, 2012 at 8:19 PM, Antoine Pitrou <rep...@bugs.python.org> wrote:
> If I read your [Martin v. Löwis' ] patch correctly, collisions will > produce additional allocations ... That's a pretty massive > change in memory consumption for string dicts Not in practice. The point I first missed is that this triggers only when the hash is *fully* equal; if the hashes are merely equal after masking, then today's try-another-slot approach will still be used, even for strings. Per ( http://bugs.python.org/issue13703#msg151850 ) Marc-Andre Lemburg's measurements, full-hash equality explains only 1 in 10,000 collisions. From a performance standpoint, we can almost ignore a case that rare; it is almost certainly dwarfed by resizing. I *am* a bit concerned that the possible contents of a dictentry change; this could cause easily-missed-in-testing breakage for anything that treats table as an array. That said, it doesn't seem much worse than the search finger, and there seemed to be recent consensus that even promising an exact dict -- subclasses not allowed -- didn't mean that direct access was sanctioned. So it still seems safer than changing the de-facto iteration order. ---------- _______________________________________ 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
