[Numpy-discussion] exponentiation q.

Pauli Virtanen pav@iki...
Fri Jul 25 15:39:34 CDT 2008


Fri, 25 Jul 2008 16:24:35 -0400, Gideon Simpson wrote:
> How does python (or numpy/scipy) do exponentiation?  If I do x**p, where
> p is some positive integer, will it compute x*x*...*x (p times), or will
> it use logarithms?

For floats it will call operating system's pow, which supposedly is 
optimized.

For integer powers |n| < 100 of complex numbers it computes the power by 
repeated squarings and multiplications using a binary decomposition, and 
for larger |n| falls back to using a logarithm.

For integer powers of integers, it also appears to use repeated squarings 
and multiplications according to a binary decomposition.

-- 
Pauli Virtanen



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