Dave Malcolm <dmalc...@redhat.com> added the comment: On Sat, 2012-01-21 at 22:20 +0000, Antoine Pitrou wrote:
> Sounds a bit overkill, and it shouldn't be a public API (which > __methods__ are). Even a private API on dicts would quickly become > visible, since dicts are so pervasive. Fair enough. > > > > Caveats: > > > > * no overflow handling (what happens after 2**32 modifications to a > > > > long-lived dict on a 32-bit build?) - though that's fixable. > > > > > > How do you suggest to fix it? > > > > If the dict is heading towards overflow of these counters, it's either > > long-lived, or *huge*. > > > > Possible approaches: > > (a) use 64-bit counters rather than 32-bit, though that's simply > > delaying the inevitable > > Well, even assuming one billion lookup probes per second on a single > dictionary, the inevitable will happen in 584 years with a 64-bit > counter (but only 4 seconds with a 32-bit counter). > > A real issue, though, may be the cost of 64-bit arithmetic on 32-bit > CPUs. > > > (b) when one of the counters gets large, divide both of them by a > > constant (e.g. 2). We're interested in their ratio, so dividing both by > > a constant preserves this. > > Sounds good, although we may want to pull this outside of the critical > loop. OK; I'll look at implementing (b). Oops, yeah, that was a typo; I meant 0 to disable. > - 0 to disable it > - 1 to enable it and use the default scaling factor > - >= 2 to enable it and set the scaling factor You said above that it should be hardcoded; if so, how can it be changed at run-time from an environment variable? Or am I misunderstanding. Works for me. > > BTW, presumably if we do it, we should do it for sets as well? > > Yeah, and use the same env var / sys function. Despite the "DICT" in the title? OK. Thanks for the feedback. ---------- _______________________________________ 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
