mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-08-04 08:59:19 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 11

bpo-35588: Speed up mod, divmod and floordiv operations for Fraction type (#11322)

Browse source 
* bpo-35588: Implement mod and divmod operations for Fraction type by spelling out the numerator/denominator calculation, instead of instantiating and normalising Fractions along the way. This speeds up '%' and divmod() by 2-3x.

* bpo-35588: Also reimplement Fraction.__floordiv__() using integer operations to make it ~4x faster.

* Improve code formatting.

Co-Authored-By: scoder <stefan_ml@behnel.de>

* bpo-35588: Fix return type of divmod(): the result of the integer division should be an integer.

* bpo-35588: Further specialise __mod__() and inline the original helper function _flat_divmod() since it's no longer reused.

* bpo-35588: Add some tests with large numerators and/or denominators.

* bpo-35588: Use builtin "divmod()" function for implementing __divmod__() in order to simplify the implementation, even though performance results are mixed.

* Rremove accidentally added empty line.

* bpo-35588: Try to provide more informative output on test failures.

* bpo-35588: Improve wording in News entry.

Co-Authored-By: scoder <stefan_ml@behnel.de>

* Remove stray space.
This commit is contained in:
Stefan Behnel 2019-01-02 13:22:06 +01:00 • committed by Serhiy Storchaka
parent a1d1425306
commit 3a374e0c5a
3 changed files with 63 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

14
Lib/fractions.py
View file

@ -429,14 +429,22 @@ class Fraction(numbers.Rational):
def _floordiv(a, b):
"""a // b"""
return math.floor(a / b)
return (a.numerator * b.denominator) // (a.denominator * b.numerator)
__floordiv__, __rfloordiv__ = _operator_fallbacks(_floordiv, operator.floordiv)
def _divmod(a, b):
"""(a // b, a % b)"""
da, db = a.denominator, b.denominator
div, n_mod = divmod(a.numerator * db, da * b.numerator)
return div, Fraction(n_mod, da * db)
__divmod__, __rdivmod__ = _operator_fallbacks(_divmod, divmod)
def _mod(a, b):
"""a % b"""
div = a // b
return a - b * div
da, db = a.denominator, b.denominator
return Fraction((a.numerator * db) % (b.numerator * da), da * db)
__mod__, __rmod__ = _operator_fallbacks(_mod, operator.mod)