[issue18719] Remove false optimizaton for equality comparison of hashed strings

Roundup Robot added the comment: New changeset ac2f59a6637f by Raymond Hettinger in branch '2.7': Issue 18719: Remove a false optimization http://hg.python.org/cpython/rev/ac2f59a6637f -- ___ Python tracker ___

[issue18719] Remove false optimizaton for equality comparison of hashed strings

Roundup Robot added the comment: New changeset 8f9bc9283400 by Raymond Hettinger in branch '3.3': Issue 18719: Remove a false optimization http://hg.python.org/cpython/rev/8f9bc9283400 -- nosy: +python-dev ___ Python tracker

[issue18719] Remove false optimizaton for equality comparison of hashed strings

Changes by Raymond Hettinger : Added file: http://bugs.python.org/file31270/27.diff ___ Python tracker ___ ___ Python-bugs-list mailing list U

[issue18719] Remove false optimizaton for equality comparison of hashed strings

Changes by Raymond Hettinger : -- versions: +Python 2.7, Python 3.3 ___ Python tracker ___ ___ Python-bugs-list mailing list Unsubscri

[issue18719] Remove false optimizaton for equality comparison of hashed strings

Alex Gaynor added the comment: The statistic that htis is *never* hit across a large python program is great evidence that this isn't useful. +1 on removing from me. -- ___ Python tracker _

[issue18719] Remove false optimizaton for equality comparison of hashed strings

Raymond Hettinger added the comment: Profiling the test suite shows that the short-cut branch NEVER gets taken. There are no cases where the string lengths, kinds, and 64-bit hashes match, but the stings themselves are a mismatch. The whole theory behind this optimization is invalid. The firs

[issue18719] Remove false optimizaton for equality comparison of hashed strings

STINNER Victor added the comment: See also issues #16286 and #17628. -- ___ Python tracker ___ ___ Python-bugs-list mailing list Unsub

[issue18719] Remove false optimizaton for equality comparison of hashed strings

Alex Gaynor added the comment: does this show demonstrable results (in either direction) on stringbench or the benchmarks repo? -- nosy: +alex ___ Python tracker ___ ___

[issue18719] Remove false optimizaton for equality comparison of hashed strings

Changes by Antoine Pitrou : -- nosy: +haypo, serhiy.storchaka ___ Python tracker ___ ___ Python-bugs-list mailing list Unsubscribe: h

[issue18719] Remove false optimizaton for equality comparison of hashed strings

New submission from Raymond Hettinger: This code is only run when the kinds, lengths, and hashes match. So, the probability of the strings being equal is VERY high. Accordingly, there is no benefit to an earlier out test to see if the first characters differ. There is a modest benefit to com

[issue18719] Remove false optimizaton for equality comparison of hashed strings

Changes by Raymond Hettinger : -- components: Interpreter Core nosy: rhettinger priority: normal severity: normal status: open title: Remove false optimizaton for equality comparison of hashed strings versions: Python 3.4 ___ Python tracker