Raymond Hettinger <[email protected]> added the comment:
Note that Fraction arithmetic has a huge administrative overhead. The cost of
the underlying multiplications and divisions won't dominate the total time
until the numerators and denominators are very large.
For the proposed optimization, this implies that cost for the extra Python
steps to implement the optimization will be negligible. The benefits of the
optimization are similarly attenuated.
-- Update to experimentation code: add guards for the relatively prime case. --
class Henrici(Fraction):
'Reformulate _mul to reduce the size of intermediate products'
def _mul(a, b):
a_n, a_d = a.numerator, a.denominator
b_n, b_d = b.numerator, b.denominator
d1 = math.gcd(a_n, b_d)
if d1 > 1:
a_n //= d1
b_d //= d1
d2 = math.gcd(b_n, a_d)
if d2 > 1:
b_n //= d2
a_d //= d2
result = Fraction(a_n * b_n, a_d * b_d, _normalize=False)
assert math.gcd(a_n * b_n, a_d * b_d) == 1 and a_d * b_d >= 0
return result
----------
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Python tracker <[email protected]>
<https://bugs.python.org/issue43420>
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