July 25, 2008
8:39 p.m.
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