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GeezerVison is showing github.com — gh-100239: use PyFloat_AS_DOUBLE and _PyLong_IsZero in the float / compactlong specializations by chris-eibl · Pull Request #144826 · python/cpython

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@chris-eibl

@chris-eibl chris-eibl commented Feb 14, 2026 •
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Since we know that we deal with exact floats here.

This is just a small follow-up on #128722 and #128963.

I don't think it deserves a news entry, but I'd happily create it if deemed meaningful enough.

Microbenchmark from @iritkatriel 's PR:

Old:

>>> timeit("for i in range(10000):\n\tb = a+i", number=100000, setup="a = 1.0")
42.05178890001844
>>> timeit("for i in range(10000):\n\tb = i+a", number=100000, setup="a = 1.0")
41.31541720000678

New:

>>> timeit("for i in range(10000):\n\tb = a+i", number=100000, setup="a = 1.0")
38.316913699993165
>>> timeit("for i in range(10000):\n\tb = i+a", number=100000, setup="a = 1.0")
38.37592560000485

Fastmark results are within the noise 1, the three arithmetic benchmarks @Fidget-Spinner mentioned are a tad faster:

diff

  • Issue: Specialize long tail of binary operations using a table. #100239

Footnotes

  1. see my gist how I do them ↩

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@chris-eibl
use PyFloat_AS_DOUBLE and _PyLong_IsZero since we
075c2a8 
know that we deal with exact floats here
@bedevere-app bedevere-app Bot added the awaiting review label Feb 14, 2026
@bedevere-app bedevere-app Bot mentioned this pull request Feb 14, 2026
Specialize long tail of binary operations using a table. #100239
Open
@chris-eibl chris-eibl added the skip news label Feb 14, 2026
@chris-eibl
chris-eibl requested a review from iritkatriel February 14, 2026 20:02
@chris-eibl

chris-eibl commented Feb 14, 2026

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This microbenchmark

import time


def bench():
    t = time.perf_counter()
    f = 1.0
    for i in range(60000):
        for j in range(1, 1000):
            f = f + j
            f = f - j
            f = f / j
            f = f * j
    print(time.perf_counter() - t)


if __name__ == "__main__":
    bench()

shows even better speedup:

old: 6.5 seconds
new: 5.5 seconds
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@chris-eibl
chris-eibl requested a review from Eclips4 February 14, 2026 20:21
skirpichev
skirpichev approved these changes Feb 15, 2026
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@bedevere-app bedevere-app Bot added awaiting core review and removed awaiting review labels Feb 15, 2026
@skirpichev

skirpichev commented Feb 15, 2026

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I don't think it deserves a news entry, but I'd happily create it if deemed meaningful enough.

This is user-visible change. So, I believe it deserves a news entry.
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chris-eibl added 2 commits February 17, 2026 20:55
@chris-eibl
Merge branch 'main' into float_exact
27d1858
@chris-eibl
add news
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chris-eibl
chris-eibl commented Feb 17, 2026
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Comment thread Misc/NEWS.d/next/Core_and_Builtins/2026-02-17-21-04-03.gh-issue-100239.LyVabQ.rst
@@ -0,0 +1,2 @@
Speedup ``BINARY_OP_EXTEND`` for exact floats and medium-size integers by up

@chris-eibl chris-eibl Feb 17, 2026

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Compact ints are an implementation detail and the term medium-size integers has been chosen in news entries in the past for them.

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@chris-eibl chris-eibl removed the skip news label Feb 17, 2026
Eclips4
Eclips4 approved these changes Feb 19, 2026
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Thank you Chris!

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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting core review labels Feb 19, 2026
@Eclips4
Eclips4 merged commit b5c8e6e into python:main Feb 19, 2026
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@bedevere-app bedevere-app Bot removed the awaiting merge label Feb 19, 2026
@chris-eibl
chris-eibl deleted the float_exact branch February 19, 2026 19:59
brijkapadia pushed a commit to brijkapadia/cpython that referenced this pull request Feb 28, 2026
@chris-eibl @brijkapadia
pythongh-100239: Use PyFloat_AS_DOUBLE and _PyLong_IsZero` in t…
c155613 
…he float / compactlong specializations (python#144826)
ljfp pushed a commit to ljfp/cpython that referenced this pull request Apr 25, 2026
@chris-eibl @ljfp
pythongh-100239: Use PyFloat_AS_DOUBLE and _PyLong_IsZero` in t…
c33f46d 
…he float / compactlong specializations (python#144826)
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@skirpichev skirpichev skirpichev approved these changes
@Eclips4 Eclips4 Eclips4 approved these changes
@iritkatriel iritkatriel Awaiting requested review from iritkatriel

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3 participants

@chris-eibl @skirpichev @Eclips4
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