[Numpy-discussion] method to calculate the magnitude squared

Nathaniel Smith njs at pobox.com
Sat Oct 10 14:29:22 EDT 2015

On Oct 10, 2015 10:50 AM, "Charles R Harris" <charlesr.harris at gmail.com>
> On Sat, Oct 10, 2015 at 11:14 AM, Marten van Kerkwijk <
m.h.vankerkwijk at gmail.com> wrote:
>> > We tend to avoid adding methods. 2) would be a very easy enhancement,
just a slight modification of sqr.
>> Did you mean `np.square`? Sadly, that doesn't do the right thing:
`np.square(1+1j)` yields `2j`, while one wants `c*c.conj()` and thus `2`.
Or, for fastest speed, really just `c.real**2 + c.imag**2`.
> Yes, I meant the new function could made by reusing the square code with
slight modifications.
>> My guess would be that a new ufunc, say `np.abs2` or `np.modulus2` or
so, would be more appropriate than defining a new method. I'd also be
hesitant to define a new private method -- I like how those usually are
just used to override python basics.
> Julia uses abs2.

I don't have an opinion on whether abs2 is important enough to bother with
(I don't work much with complex numbers myself, nor have I run any
benchmarks), but I agree that if we do want it then adding it as a regular
ufunc would definitely be the right approach.

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