[New-bugs-announce] [issue43198] Operations on sets more than hundred times less efficient with python3.9 than with previous versions

[Eric Martin]

New submission from Eric Martin <eric.martin at unsw.edu.au>:

Run on a MacBook Pro (15-inch, 2019)
         2.3 GHz 8-Core Intel Core i9
         16 GB 2400 MHz DDR4


Python 3.8.7 (default, Dec 24 2020, 19:07:18) 
[Clang 12.0.0 (clang-1200.0.32.27)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from timeit import timeit
>>> S = set(range(10_000))
>>> timeit('S.remove(5000); S.add(5000)', globals=globals(), number=100_000)
0.01933291699999984

$ python3.9
Python 3.9.1 (default, Dec  8 2020, 13:10:53) 
[Clang 12.0.0 (clang-1200.0.32.27)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from timeit import timeit
>>> S = set(range(10_000))
>>> timeit('S.remove(5000); S.add(5000)', globals=globals(), number=100_000)
3.8517225489999998

----------
components: Interpreter Core
messages: 386815
nosy: eamartin
priority: normal
severity: normal
status: open
title: Operations on sets more than hundred times less efficient with python3.9 than with previous versions
type: performance
versions: Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue43198>
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