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gh-72902: improve Fraction constructor speed for typical inputs #134320

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Merged
merged 1 commit into from
May 20, 2025
Merged

gh-72902: improve Fraction constructor speed for typical inputs #134320

merged 1 commit into from
May 20, 2025

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skirpichev
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@skirpichev skirpichev commented May 20, 2025 •
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This moves abc check for numbers.Rational - down.

Benchmark ref patch
Fraction(myint) 5.62 us 7.03 us: 1.25x slower
Fraction(Fraction(1, 2)) 5.89 us 4.88 us: 1.21x faster
Fraction(Decimal('0.25')) 11.1 us 7.98 us: 1.39x faster
Fraction(IntSubclass(123)) 5.93 us 5.05 us: 1.17x faster
Fraction(FloatSubclass(0.25)) 7.69 us 4.26 us: 1.81x faster
Fraction('123') 19.2 us 16.1 us: 1.19x faster
Fraction('1/3') 19.6 us 16.4 us: 1.20x faster
Fraction('1.2e-3') 26.1 us 23.0 us: 1.14x faster
Fraction('-.2') 23.4 us 20.2 us: 1.16x faster
Geometric mean (ref) 1.21x faster 
# bench.py
import pyperf
from fractions import Fraction as F
from decimal import Decimal as D
from numbers import Integral

runner = pyperf.Runner()
s = 'Fraction'
class MyInt:
    numerator = 123
    denominator = 1
    def __int__(self):
        return 123
    def __repr__(self):
        return "myint"
class IntSubclass(int):
    def __repr__(self):
        return 'IntSubclass('+super().__repr__()+')'
class FloatSubclass(float):
    def __repr__(self):
        return 'FloatSubclass('+super().__repr__()+')'

Integral.register(MyInt)
for v in [MyInt(), F(1, 2), D("0.25"),
          IntSubclass(123), FloatSubclass(0.25),
          "123", "1/3", "1.2e-3", "-.2"]:
    r = s + '(' + repr(v) + ')'
    runner.bench_func(r, F, v)

@skirpichev
pythongh-72902: improve Fraction constructor speed for typical inputs
1c67935 
This moves abc check for numbers.Rational - down.
@bedevere-app bedevere-app bot mentioned this pull request May 20, 2025
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@skirpichev skirpichev mentioned this pull request May 20, 2025
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@eendebakpt
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There is a slight behaviour change here: for Fraction subclasses the construction now goes via .as_integer_ratio, instead of via .numerator and .denumerator (for this reason the benchmark Fraction(Fraction(1, 2)) is improving).

A minimal example:

import fractions

class MyFraction(Fraction):
    @property
    def numerator(self):
        print('he!')
        return super().numerator

f = MyFraction(1,2)
Fraction(f)

I think the change is acceptable and would probably accept the PR.

@skirpichev
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>>> help(fractions.Fraction.as_integer_ratio)
Help on function as_integer_ratio in module fractions:

as_integer_ratio(self)
    Return a pair of integers, whose ratio is equal to the original Fraction.

    The ratio is in lowest terms and has a positive denominator.

serhiy-storchaka
serhiy-storchaka approved these changes May 20, 2025
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LGTM. 👍

@serhiy-storchaka serhiy-storchaka merged commit 175ba36 into python:main May 20, 2025
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@skirpichev skirpichev deleted the speedup-Fraction branch May 20, 2025 11:02
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@serhiy-storchaka serhiy-storchaka serhiy-storchaka approved these changes

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@skirpichev @eendebakpt @serhiy-storchaka