Status: Valid
Owner: ----
Labels: Type-Defect Priority-Medium EasyToFix
New issue 3516 by [email protected]: gcd for Rationals is much slower than
it should be
http://code.google.com/p/sympy/issues/detail?id=3516
There is a routine in Mul (at the bottom) named _rgcd that computes the
Rational gcd much faster than the current gcd() or .gcd() involving only
Rationals.
timeit('gcd(S.Half,S.Half/2)','from sympy import S,gcd',number=1000)
0.52889084815979
>>> timeit('S.Half.gcd(S.Half/2)','from sympy import S',number=1000)
0.4783451557159424
>>> timeit('Rational(igcd(a.p,b.p),ilcm(a.q,b.q)),S.Half,S.Half/2','from
... sympy import ilcm, igcd, Rational, S\na = S.Half; b=a/2;
... c=a*4;d=a*5',number=1000)
0.05577492713928223
Right now, the .gcd() involving Rationals uses the default definition in
Number; it should probably have it's own method in Rational or a smarting
function in polytools.
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