On Sun, Mar 5, 2017 at 9:25 PM Tim Peters <tim.pet...@gmail.com> wrote:
> > Would someone please move the patch along? I expect it's my fault it's > languished so long, since I'm probably the natural person to review it, but > I've been buried under other stuff. > > But the patch doesn't change anything about the sorting algorithm itself - > even shallow knowledge of how timsort works is irrelevant. It's just > plugging in a different bottom-level object comparison _function_ when that > appears valuable. > > I've said from the start that it's obvious (to me ;-) ) that it's an > excellent tradeoff. At worst it adds one simple (pre)pass over the list > doing C-level pointer equality comparisons. That's cheap. The worst-case > damage is obviously small, the best-case gain is obviously large, and the > best cases are almost certainly far more common than the worst cases in > most code. > Thank you so much for the support! Yes to all of those things! > > In reviewing my own code, after it was fiddled to work under Python 3 > there are no mixed-type lists that are ever sorted. There are lists with > complex objects, but whenever those are sorted there's a `key=` argument > that reduces the problem to sorting ints or tuples of builtin scalar types. > I'm adding that quote to the next version my poster :) > > One subtle thing to look at: thread safety. IIRC, the patch plugged the > comparison function into a file global. That's obviously hosed if multiple > threads sort different kinds of lists simultaneously. > Wow, that is a *very* good point. I never think about those kinds of things, being a n00b, so thanks for catching that... I'll have to go in an fix that. I'm not sure how, though, because the ISLT macro gets called in a bunch of different functions. The only way I can think of to fix it would be to pass the function pointer as an argument to *all* the functions that use ISLT, which would be pretty messy. What do you think would be the easiest fix? Thanks! Elliot
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