[Numpy-discussion] optimizing power() for complex and real cases
Gary Ruben
gruben at bigpond.net.au
Wed Feb 15 15:27:08 CST 2006
Tim Hochberg wrote:
<big snip>
> As I've been thinking about this some more, I think the correct thing to
> do is not to mess with the power ufuncs at all. Rather in x.__pow__
> (since I don't know that there's anywhere else to do it), after the
> above checks check the types of the array and in the cases where the
> first argument is a float or complex and the second argument is some
> sort of integer array. This would be dispatched to some other helper
> function instead of the normal pow_ufunc. In other words, optimize:
>
> A**2, A**2.0, A**(2.0+0j), etc
>
> and
>
> A**array([1,2,3])
>
> but not
>
> A**array[1.0, 2.0, 3.0]
>
> I think that this takes care of the optimization slowing down power for
> general floats and optimizes the only array-array case that really matter.
I think this might still be a tiny bit dangerous despite not observing
monotonicity problems and would be a bit more conservative and change it to:
optimize:
A**2, A**(2+0j), etc
and
A**array([1,2,3])
but not
A**array[1.0, 2.0, 3.0], A**2.0, A**(2.0+0j)
--
Gary R.
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