Antoine Pitrou <pit...@free.fr> added the comment: > I wonder if the dict statistics should be exposed with extra attributes > or a method on the dict; e.g. a __stats__ attribute, something like > this: > > LargeDictStats(keys=58, mask=127, insertions=53, iterations=1697) > > SmallDictStats(keys=3, mask=7)
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. > > > 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. > By "a constant" do you mean from the perspective of big-O notation, or > do you mean that it should be hardcoded (I was wondering if it should be > a sys variable/environment variable etc?). Hardcoded, as in your patch. > > There needs to be a way to disable it: an environment variable would be > > the minimum IMO. > > e.g. set it to 0 to enable it, set it to nonzero to set the scale > factor. 0 to enable it sounds misleading. I'd say: - 0 to disable it - 1 to enable it and use the default scaling factor - >= 2 to enable it and set the scaling factor > Any idea what to call it? PYTHONDICTPROTECTION ? Most people should either enable or disable it, not change the scaling factor. > BTW, presumably if we do it, we should do it for sets as well? Yeah, and use the same env var / sys function. ---------- _______________________________________ 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
