10000 bpo-43420: Simple optimizations for Fraction's arithmetics by skirpichev · Pull Request #24779 · python/cpython · GitHub
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bpo-43420: Simple optimizations for Fraction's arithmetics #24779

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Merged
merged 13 commits into from
Mar 22, 2021
Merged

bpo-43420: Simple optimizations for Fraction's arithmetics #24779

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598b3c9
Merge Fraction._add/sub() to a common helper _add_sub_()
skirpichev Mar 11, 2021
430e476
bpo-43420: Simple optimizations for Fraction's arithmetics
skirpichev Mar 14, 2021
046c84e
Use Fraction's private attributes in arithmetic methods
skirpichev Mar 14, 2021
772bec6
Rational addition/substraction: special-case g2 == 1
skirpichev Mar 15, 2021
3d5d321
Special-case for trivial gcd in Fraction._mul()/_div() as well
skirpichev Mar 16, 2021
32778ab
Amend _add_sub_() comment for fractions, obtained from floats
skirpichev Mar 16, 2021
ea38398
Revert "Use Fraction's private attributes in arithmetic methods"
skirpichev Mar 17, 2021
f4b151a
Revert 598b3c9630 & make _add()/_sub() less nested
skirpichev Mar 17, 2021
40401af
Apply spelling fixes
skirpichev Mar 18, 2021
020037a
Restore back initial d test in _div() per Mark suggestion
skirpichev Mar 18, 2021
bde52d1
Add coverage tests (missing in test_fractions.py)
skirpichev Mar 18, 2021
51b52b6
Merge branch 'master' into opt-fractions
skirpichev Mar 20, 2021
2789350
Update Misc/ACKS
skirpichev Mar 20, 2021
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Use Fraction's private attributes in arithmetic methods 
That's slightly faster for small components.

Before:
$ ./python -m timeit -r11 -s 'from fractions import Fraction as F' \
-s 'a = F(10, 3)' -s 'b = F(6, 5)' 'a + b'
20000 loops, best of 11: 12.1 usec per loop
$ ./python -m timeit -r11 -s 'from fractions import Fraction as F' \
-s 'a = F(10, 3)' -s 'b = 7' 'a + b'
20000 loops, best of 11: 11.4 usec per loop

After:
$ ./python -m timeit -r11 -s 'from fractions import Fraction as F' \
-s 'a = F(10, 3)' -s 'b = F(6, 5)' 'a + b'
50000 loops, best of 11: 9.74 usec per loop
$ ./python -m timeit -r11 -s 'from fractions import Fraction as F' \
-s 'a = F(10, 3)' -s 'b = 7' 'a + b'
20000 loops, best of 11: 16.5 usec per loop

On the master:
$ ./python -m timeit -r11 -s 'from fractions import Fraction as F' \
-s 'a = F(10, 3)' -s 'b = F(6, 5)' 'a + b'
50000 loops, best of 11: 9.61 usec per loop
$ ./python -m timeit -r11 -s 'from fractions import Fraction as F' \
-s 'a = F(10, 3)' -s 'b = 7' 'a + b'
50000 loops, best of 11: 9.11 usec per loop
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@skirpichev
skirpichev committed Mar 14, 2021
commit 046c84e8f970306b668d62cfacbd58f65b8c6e66
21 changes: 12 additions & 9 deletions Lib/fractions.py
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Original file line number Diff line number Diff line change
Expand Up @@ -355,8 +355,10 @@ class doesn't subclass a concrete type, there's no

"""
def forward(a, b):
if isinstance(b, (int, Fraction)):
if isinstance(b, Fraction):
return monomorphic_operator(a, b)
elif isinstance(b, int):
return monomorphic_operator(a, Fraction(b))
elif isinstance(b, float):
return fallback_operator(float(a), b)
elif isinstance(b, complex):
Expand All @@ -367,9 +369,10 @@ def forward(a, b):
forward.__doc__ = monomorphic_operator.__doc__

def reverse(b, a):
if isinstance(a, numbers.Rational):
# Includes ints.
if isinstance(a, Fraction):
return monomorphic_operator(a, b)
elif isinstance(a, numbers.Integral):
return monomorphic_operator(Fraction(a), b)
elif isinstance(a, numbers.Real):
return fallback_operator(float(a), float(b))
elif isinstance(a, numbers.Complex):
Expand Down Expand Up @@ -444,8 +447,8 @@ def reverse(b, a):
# common factors are removed by g1 == gcd(na, db).

def _add_sub_(a, b, pm=int.__add__):
na, da = a.numerator, a.denominator
nb, db = b.numerator, b.denominator
na, da = a._numerator, a._denominator
nb, db = b._numerator, b._denominator
g = math.gcd(da, db)
if g == 1:
return Fraction(pm(na * db, da * nb), da * db, _normalize=False)
Expand All @@ -465,8 +468,8 @@ def _add_sub_(a, b, pm=int.__add__):

def _mul(a, b):
"""a * b"""
na, da = a.numerator, a.denominator
nb, db = b.numerator, b.denominator
na, da = a._numerator, a._denominator
nb, db = b._numerator, b._denominator
g1 = math.gcd(na, db)
g2 = math.gcd(nb, da)
return Fraction((na // g1) * (nb // g2),
Expand All @@ -477,8 +480,8 @@ def _mul(a, b):
def _div(a, b):
"""a / b"""
# Same as _mul(), with inversed b.
na, da = a.numerator, a.denominator
nb, db = b.numerator, b.denominator
na, da = a._numerator, a._denominator
nb, db = b._numerator, b._denominator
g1 = math.gcd(na, nb)
g2 = math.gcd(db, da)
n, d = (na // g1) * (db // g2), (nb // g1) * (da // g2)
Expand Down
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