Issue 31108: add contains for list_iterator (and others) for better performance (original) (raw)

Created on 2017-08-02 18:53 by sir-sigurd, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Messages (6)
msg299666 - (view)	Author: Sergey Fedoseev (sir-sigurd) *	Date: 2017-08-02 18:53
> python -mtimeit -s "l = list(range(100000))" "l[-1] in l" 1000 loops, best of 3: 1.34 msec per loop > python -mtimeit -s "l = list(range(100000))" "l[-1] in iter(l)" 1000 loops, best of 3: 1.59 msec per loop
msg299686 - (view)	Author: Serhiy Storchaka (serhiy.storchaka) *	Date: 2017-08-03 06:32
The patch adds almost 40 line of the code and increases the performance of not well famous feature at best by 10-20%. Adding an optimization for every new iterator type will add a comparable quantity of the code. I think this is too high cost. Using a common template implementation for iterators () would decrease the relative cost of this feature.
msg299773 - (view)	Author: Serhiy Storchaka (serhiy.storchaka) *	Date: 2017-08-05 04:38
Terry, this proposition doesn't change the behavior. It moves the iterator forward during searching. The only effect is inlining __next__ in a loop and getting rid of the overhead of few indirections and calls.
msg299774 - (view)	Author: Terry J. Reedy (terry.reedy) *	Date: 2017-08-05 04:56
Sorry, I mistakenly assumed, without carefully checking the C code, that the speedup was from checking the underlying collection, without advancing the iterator. I presume that " ++it->it_index;" is the statement to the contrary. I should have either asked or found this sooner. I unlinked the noisy comment.
msg301022 - (view)	Author: Antoine Pitrou (pitrou) *	Date: 2017-08-30 11:46
I don't think I've ever used `in` on an iterator. I didn't even expect it to work, and would not consider its use a good practice.
msg301040 - (view)	Author: Raymond Hettinger (rhettinger) *	Date: 2017-08-31 07:03
I recommend rejecting this proposal