I'm using the fractions module in Python v3.1 to compute the greatest common divisor. I would like to know what algorithm is used. I'm guessing the Euclidean method, but would like to be sure. The docs (http://docs.python.org/py3k/library/fractions.html?highlight=fractions.gcd#fractions.gcd) don't help. Can anybody clue me in?
According to the 3.1.2 source code online, here's gcd
as defined in Python-3.1.2/Lib/fractions.py
:
def gcd(a, b):
"""Calculate the Greatest Common Divisor of a and b.
Unless b==0, the result will have the same sign as b (so that when
b is divided by it, the result comes out positive).
"""
while b:
a, b = b, a%b
return a
So yes, it's the Euclidean algorithm, written in pure Python.