[Numpy-discussion] Integers to integer powers, let's make a decision

[josef.pktd at gmail.com]

On Fri, Jun 10, 2016 at 2:00 PM, Nathaniel Smith <njs at pobox.com> wrote:

> On Jun 10, 2016 10:50, "Alan Isaac" <alan.isaac at gmail.com> wrote:
> >
> > On 6/10/2016 1:34 PM, Nathaniel Smith wrote:
> >>
> >> You keep pounding on this example. It's a fine example, but, c'mon. **2
> is probably at least 100x more common in real source code. Maybe 1000x more
> common. Why should we break the
> >> common case for your edge case?
> >
> >
> >
> > It is hardly an "edge case".
> > Again, **almost all** integer combinations overflow: that's the point.
>
> When you say "almost all", you're assuming inputs that are uniformly
> sampled integers. I'm much more interested in what proportion of calls to
> the ** operator involve inputs that can overflow, and in real life those
> inputs are very heavily biased towards small numbers.
>
> (I also think we should default to raising an error on overflow in
> general, with a seterr switch to turn it off when desired. But that's
> another discussion...)
>

but x**2 is just x*x which some seem to recommend (I have no idea why), and
then there are not so many "common" cases left.


(However, I find integers pretty useless except in some very specific
cases. When I started to cleanup scipy.stats.distribution, I threw out
integers for discrete distributions and replaced all or most `**` by
np.power, IIRC mainly because of the old python behavior and better numpy
behavior.)

(I'd rather use robust calculations that provide correct numbers, than
chasing individual edge cases and save a bit of memory in some common
cases. scipy stats also doesn't use factorial in almost all cases, because
special.gamma and variants are more robust )


Josef


> -n
>
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