On Wed, Jan 18, 2012 at 1:05 PM, Antoine Pitrou <report@bugs.python.org>wrote: > > Antoine Pitrou <pitrou@free.fr> added the comment: > > > I like this, esp. if for old releases the collision counting is on by > > default and the hash seeding is off by default, while in 3.3 both should > be > > on by default. Different env vars or flags should be used to > enable/disable > > them. > > I would hope 3.3 only gets randomized hashing. Collision counting is a > hack to make bugfix releases 99.999%-compatible instead of 99.9% ;) > Really? I'd expect the difference to be more than 2 nines. The randomized hashing has two problems: (a) change in dict order; (b) hash varies between processes. I cannot imagine counterexamples to the collision counting that weren't constructed specifically as counterexamples.