New submission from STINNER Victor: In Python 3.4, str==str is implemented by calling memcmp().
unicode_eq() function, used by dict and set types, checks the first byte before calling memcmp(). bytes==bytes uses the same check. Py_UNICODE_MATCH macro checks the first *and* last character before calling memcmp() since this commit: --- changeset: 38242:0de9a789de39 branch: legacy-trunk user: Fredrik Lundh <fred...@pythonware.com> date: Tue May 23 10:10:57 2006 +0000 files: Include/unicodeobject.h description: needforspeed: check first *and* last character before doing a full memcmp --- Attached patch changes str==str to check the first and last character before calling memcmp(). It might reduce the overhead of a C function call, but it is much faster when comparing two different strings of the same length with a common prefix (but a different suffix). The patch merges also unicode_compare_eq() and unicode_eq() to use the same code for str, dict and set. We may use the same optimization on byte strings. See also #16321. ---------- files: unicode_eq.patch keywords: patch messages: 185956 nosy: haypo, pitrou, serhiy.storchaka priority: normal severity: normal status: open title: str==str: compare the first and last character before calling memcmp() versions: Python 3.4 Added file: http://bugs.python.org/file29668/unicode_eq.patch _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue17628> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
