[issue16562] Optimize dict equality test
Roundup Robot added the comment: New changeset d12785ecca72 by Antoine Pitrou in branch 'default': Issue #16562: Optimize dict equality testing. http://hg.python.org/cpython/rev/d12785ecca72 -- nosy: +python-dev ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16562 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16562] Optimize dict equality test
Antoine Pitrou added the comment: The patch looks correct. If the tests pass, go ahead and apply it. Done. -- nosy: +pitrou resolution: - fixed stage: patch review - committed/rejected status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16562 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16562] Optimize dict equality test
Martin v. Löwis added the comment: The patch looks good to me. -- nosy: +loewis ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16562 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16562] Optimize dict equality test
Serhiy Storchaka added the comment:
And here is a synthetic microbenchmark:
$ ./python -m timeit -s n=10**3; k=2; a={(i,)*k:i for i in range(n)};
b={(i,)*k:i for i in range(n)} a == b
Vanilla: 251 usec per loop
Patched: 195 usec per loop
$ ./python -m timeit -s n=10**3; k=2; a={(i,)*k:i for i in range(n)};
b=dict(a) a == b
Vanilla: 116 usec per loop
Patched: 58.6 usec per loop
The use of tuple keys is quite common.
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[issue16562] Optimize dict equality test
Changes by STINNER Victor victor.stin...@gmail.com: -- nosy: +haypo ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16562 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16562] Optimize dict equality test
Raymond Hettinger added the comment: The patch looks correct. If the tests pass, go ahead and apply it. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16562 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16562] Optimize dict equality test
New submission from Raymond Hettinger: The code for dict_equal() in Objects/dictobject.c currently loops over the key/value pairs in self and uses PyDict_GetItem() to check for the corresponding key/value pair in the other dictionary. This causes an unnecessary call to PyObject_Hash(). Instead, the code should loop over the key/value/hash triplets in self and do a direct lookup in the other dictionary with ep = (otherdict-ma_lookup)(otherdict, key, hash). The reuses the known hash value for the key; thereby avoiding the potentially slow call to PyObject_Hash(). See _PyDict_Contains() for an example of how to do a lookup when the hash value is already known. Note, the optimized path should be used only when PyDict_CheckExact() is true. -- components: Interpreter Core keywords: easy messages: 176453 nosy: rhettinger priority: low severity: normal status: open title: Optimize dict equality test type: performance versions: Python 3.4 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16562 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16562] Optimize dict equality test
Changes by Jesús Cea Avión j...@jcea.es: -- nosy: +jcea ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16562 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue16562] Optimize dict equality test
Serhiy Storchaka added the comment: Here is a simple patch. Note, the optimized path should be used only when PyDict_CheckExact() is true. Actually this is not needed. dict_equal() uses the same code for dict subclasses. -- keywords: +patch nosy: +serhiy.storchaka stage: - patch review Added file: http://bugs.python.org/file28137/dict_equal_hash_reuse.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue16562 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
