[Numpy-discussion] fpower ufunc

[Charles R Harris]

On Fri, Oct 21, 2016 at 1:45 AM, Sebastian Berg <sebastian at sipsolutions.net>
wrote:

> On Do, 2016-10-20 at 21:38 -0600, Charles R Harris wrote:
> >
> >
> > On Thu, Oct 20, 2016 at 9:11 PM, Nathaniel Smith <njs at pobox.com>
> > wrote:
> > > On Thu, Oct 20, 2016 at 7:58 PM, Charles R Harris
> > > <charlesr.harris at gmail.com> wrote:
> > > > Hi All,
> > > >
> > > > I've put up a preliminary PR for the proposed fpower ufunc. Apart
> > > from
> > > > adding more tests and documentation, I'd like to settle a few
> > > other things.
> > > > The first is the name, two names have been proposed and we should
> > > settle on
> > > > one
> > > >
> > > > fpower (short)
> > > > float_power (obvious)
> > >
> > > +0.6 for float_power
> > >
> > > > The second thing is the minimum precision. In the preliminary
> > > version I have
> > > > used float32, but perhaps it makes more sense for the intended
> > > use to make
> > > > the minimum precision float64 instead.
> > >
> > > Can you elaborate on what you're thinking? I guess this is because
> > > float32 has limited range compared to float64, so is more likely to
> > > see overflow? float32 still goes up to 10**38 which is <
> > > int64_max**2,
> > > FWIW. Or maybe there's some subtlety with the int->float casting
> > > here?
> > logical, (u)int8, (u)int16, and float16 get converted to float32,
> > which is probably sufficient to avoid overflow and such. My thought
> > was that float32 is something of a "specialized" type these days,
> > while float64 is the standard floating point precision for everyday
> > computation.
> >
>
>
> Isn't the behaviour we already have (e.g. such as mean).
>
> ints -> float64
> inexacts do not get upcast?
>
>
Hmm... The best way to do that would be to put the function in
`fromnumeric` and do it in python rather than as a ufunc, then for integer
types call power with `dtype=float64`. I like that idea better than the
current implementation, my mind was stuck in the ufunc universe.

Chuck
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