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GeezerVison is showing github.com — GH-100425: Note improved commutativity in sum(). by rhettinger · Pull Request #107785 · python/cpython

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@rhettinger

@rhettinger rhettinger commented Aug 8, 2023 •
edited by github-actions Bot
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  • Issue: Improve accuracy of builtin sum() for float inputs #100425

📚 Documentation preview 📚: https://cpython-previews--107785.org.readthedocs.build/

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@rhettinger
Note improved commutativity in sum().
c724e79
@rhettinger rhettinger added docs Documentation in the Doc dir skip news needs backport to 3.12 only security fixes labels Aug 8, 2023
@bedevere-bot bedevere-bot mentioned this pull request Aug 8, 2023
Improve accuracy of builtin sum() for float inputs #100425
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@bedevere-bot bedevere-bot added the awaiting core review label Aug 8, 2023
@rhettinger

rhettinger commented Aug 8, 2023

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Script to demonstrate the improvement:

from random import random
from itertools import permutations

n = 4
trials = 100

errors = 0
for i in range(trials):
    example = [random() for i in range(n)]
    if len(set(map(sum, permutations(example)))) != 1:
        errors += 1
        print(i, sorted(example))
print(f'{errors / trials * 100.0=}%')

Formerly there was a 63% error rate. Now it is zero.
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@rhettinger
rhettinger merged commit aab6f71 into python:main Aug 8, 2023
@miss-islington

miss-islington commented Aug 8, 2023

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Thanks @rhettinger for the PR 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖
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@bedevere-bot bedevere-bot removed the awaiting core review label Aug 8, 2023
@rhettinger
rhettinger deleted the sum_algo branch August 8, 2023 17:30
@bedevere-bot

bedevere-bot commented Aug 8, 2023

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GH-107787 is a backport of this pull request to the 3.12 branch.
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@bedevere-bot bedevere-bot removed the needs backport to 3.12 only security fixes label Aug 8, 2023
miss-islington pushed a commit to miss-islington/cpython that referenced this pull request Aug 8, 2023
@rhettinger @miss-islington
pythonGH-100425: Note improved commutativity in sum(). (pythonGH-107785)
adb32cd 
(cherry picked from commit aab6f71)

Co-authored-by: Raymond Hettinger <[email protected]>
@enzbus enzbus mentioned this pull request Nov 10, 2023
broken link to A.Neumaier article in built-in sum comment #111933
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3 participants

@rhettinger @miss-islington @bedevere-bot
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