New submission from Serhiy Storchaka: Proposed patch makes the regular expression parser produce more optimal tree, mainly due to getting rid of non-capturing groups. This allows to apply an optimization that was forbidden before and makes the regular expression compiler producing more efficient code.
For example following expressions are transformed in more optimal form: '(?:x|y)+' -> '[xy]+' '(?:ab)|(?:ac)' -> 'a[bc]' r'[a-z]|\d' -> r'[a-z\d]' This can speed up matching by 10-25 times. $ ./python -m timeit -s "import re; p = re.compile(r'(?:x|y)+'); s = 'x'*10000" "p.match(s)" Unpatched: 500 loops, best of 5: 865 usec per loop Patched: 5000 loops, best of 5: 84.5 usec per loop $ ./python -m timeit -s "import re; p = re.compile(r'(?:[a-z]|\d)+'); s = 'x'*10000" "p.match(s)" Unpatched: 100 loops, best of 5: 2.19 msec per loop Patched: 5000 loops, best of 5: 84.5 usec per loop ---------- assignee: serhiy.storchaka components: Library (Lib), Regular Expressions messages: 293477 nosy: ezio.melotti, mrabarnett, serhiy.storchaka priority: normal severity: normal stage: patch review status: open title: Optimize out non-capturing groups type: performance versions: Python 3.7 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue30340> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
