[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

Raymond Hettinger added the comment: > Serhiy, Gregory, Raymond, Antoine: so what is your feeling on > this issue? Is it worth it? I don't think it is worth it. There may be some cases that benefit, but it adds extra branching code to the common cases (sets and dicts) that already have the i

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

STINNER Victor added the comment: If it's hard to see a real speedup, it's probably not interesting to use the hash in string comparison. -- resolution: -> invalid status: open -> closed ___ Python tracker __

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

STINNER Victor added the comment: (oops, I didn't want to close the issue, it's a mistake) -- resolution: invalid -> status: closed -> open ___ Python tracker ___ __

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

STINNER Victor added the comment: I ran pybench with the patch. I don't understand this result (10% slower with the patch): DictWithStringKeys:28ms25ms +10.7%28ms26ms +10.5% This test doesn't use unicode_compare_eq() from Objects/unicodeobject.c but unicode_eq() from Objects

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

STINNER Victor added the comment: Serhiy, Gregory, Raymond, Antoine: so what is your feeling on this issue? Is it worth it? -- ___ Python tracker ___ ___

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

STINNER Victor added the comment: I added recently a new _PyUnicode_CompareWithId() function: changeset 77bebcf5c4cf (issue #19512). This function can be used instead of PyUnicode_CompareWithASCIIString() when the right parameter is a common string. It is interesting when the right string is

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

STINNER Victor added the comment: Results of benchmarks using compare_hash-3.patch: $ time ../benchmarks/perf.py -r -b default ./pythonorig ./pythonhash INFO:root:Skipping benchmark slowspitfire; not compatible with Python 3.4 INFO:root:Skipping benchmark slowpickle; not compatible with Python

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

STINNER Victor added the comment: I applied changes unrelated to the hash. -- Added file: http://bugs.python.org/file32493/compare_hash-3.patch ___ Python tracker ___ ___

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

Roundup Robot added the comment: New changeset da9c6e4ef301 by Victor Stinner in branch 'default': Issue #16286: remove duplicated identity check from unicode_compare() http://hg.python.org/cpython/rev/da9c6e4ef301 -- ___ Python tracker

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

Roundup Robot added the comment: New changeset 5fa291435740 by Victor Stinner in branch 'default': Issue #16286: optimize PyUnicode_RichCompare() for identical strings (same http://hg.python.org/cpython/rev/5fa291435740 -- ___ Python tracker

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

Roundup Robot added the comment: New changeset 536a7c09c7fd by Victor Stinner in branch 'default': Issue #16286: write a new subfunction bytes_compare_eq() http://hg.python.org/cpython/rev/536a7c09c7fd -- nosy: +python-dev ___ Python tracker

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

STINNER Victor added the comment: Updated patch. -- Added file: http://bugs.python.org/file32445/compare_hash-2.patch ___ Python tracker ___ _

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

STINNER Victor added the comment: """ (4) str in __all__ (list of str): os.py: if "putenv" not in __all__: __all__.append("putenv") """ For this example: "putenv" is probably interned by "def putenv(...)". "putenv" string and the name of the function are the same constant. When a

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

STINNER Victor added the comment: Let's try to identify some use cases in the Python test suite using gdb: (gdb) b unicode_compare_eq (gdb) condition 1 ((PyASCIIObject*)str1)->hash != -1 && ((PyASCIIObject*)str2)->hash != -1 && ((PyASCIIObject*)str1)->hash != ((PyASCIIObject*)str2)->hash (gd

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

STINNER Victor added the comment: >> That raises the question of what strings ever have had their hash >> already computed if the string hasn't been interned or has been used >> in a dict or set? > > Currently, none, I think. Strings are used (and compared) outside dict and set. -- ___

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

Antoine Pitrou added the comment: > That raises the question of what strings ever have had their hash > already computed if the string hasn't been interned or has been used > in a dict or set? Currently, none, I think. -- nosy: +pitrou ___ Python tra

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

STINNER Victor added the comment: "I will benchmark the overhead of memcmp() on short strings. We may check the first and last characters before calling memcmp() to limit the overhead of calling a function." I created the issue #17628 for this point. --

[issue16286] Use hash if available to optimize a==b and a!=b for bytes and str

Changes by STINNER Victor : -- title: Optimize a==b and a!=b for bytes and str -> Use hash if available to optimize a==b and a!=b for bytes and str ___ Python tracker ___ __