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GeezerVison is showing github.com — GH-100425: Timing experiment: For builtin_sum, try replacing Fast2Sum with 2Sum by rhettinger · Pull Request #100860 · python/cpython

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@rhettinger

@rhettinger rhettinger commented Jan 8, 2023 •
edited by bedevere-bot
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On the Apple M1 Max, this change makes no difference. I get 303/304 nsec per loop before and after the edit.

Would anyone care to run this on their builds and report back the results?

% ./python.exe -m timeit -r21 -s 'n=100' -s 'from random import expovariate as r' -s 'v1=[r(1000) + r(0.125) for i in range(n)]'   'sum(v1)'
1000000 loops, best of 21: 304 nsec per loop
  • Issue: Improve accuracy of builtin sum() for float inputs #100425

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@rhettinger
Replaced Fast2Sum with 2Sum
adeb117
@rhettinger rhettinger added the DO-NOT-MERGE label Jan 8, 2023
@rhettinger
rhettinger requested a review from mdickinson January 8, 2023 21:36
@bedevere-bot bedevere-bot added the awaiting core review label Jan 8, 2023
@hauntsaninja

hauntsaninja commented Jan 9, 2023

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I see no difference either, on Linux with an AMD Zen 2 chip
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@eendebakpt

eendebakpt commented Jan 10, 2023

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Both with and without optimizations I see no difference. System: Linux, gcc version 9.4.0 (Ubuntu 9.4.0-1ubuntu1~20.04.1), Intel(R) Core(TM) i7-4710MQ CPU @ 2.50GHz
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@rhettinger

rhettinger commented Jan 10, 2023

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Thank you both. It would be nice to hear from a Windows person as well.
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@eendebakpt

eendebakpt commented Jan 11, 2023

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Thank you both. It would be nice to hear from a Windows person as well.

On Windows (default PCbuild/build.bat, no PGO) the timings vary a lot on my system (Intel(R) Core(TM) i7-4710MQ CPU @ 2.50GHz, Windows 10, VS 2019). For this PR, measurements within 5 minutes:

image

I can confirm that the minimum time for the test is roughly the same for main and this PR.
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@rhettinger

rhettinger commented Jan 11, 2023

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Thank you. I appreciate it.

@mdickinson Given that 2Sum and Fast2Sum have the same performance in the context of builtin.sum(), do we have a non-performance reason to choose one over the other? Or should I leave the sum() code as-is?
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@rhettinger rhettinger changed the title Timing experiment: For builtin_sum, try replacing Fast2Sum with 2Sum GH-100425: Timing experiment: For builtin_sum, try replacing Fast2Sum with 2Sum Jan 12, 2023
@bedevere-bot bedevere-bot mentioned this pull request Jan 12, 2023
Improve accuracy of builtin sum() for float inputs #100425
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@mdickinson

mdickinson commented Jan 13, 2023

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@rhettinger Leaving as-is sounds good to me. The two should be functionally identical, so performance is just about the only thing that would justify choosing one over the other.
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@rhettinger rhettinger closed this Jan 13, 2023
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@mdickinson mdickinson Awaiting requested review from mdickinson

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@rhettinger @hauntsaninja @eendebakpt @mdickinson @bedevere-bot
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