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

[Sebastian Berg]

On Fr, 2016-06-10 at 20:16 +0000, Ian Henriksen wrote:
> On Fri, Jun 10, 2016 at 12:01 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...)
> > -n
> > 
> Another thing that would need separate discussion...
> Making 64 bit integers default in more cases would help here.
> Currently arange gives 32 bit integers on 64 bit Windows, but
> 64 bit integers on 64 bit Linux/OSX. Using size_t (or even
> int64_t) as the default size would help with overflows in
> the more common use cases. It's a hefty backcompat
> break, but 64 bit systems are much more common now,
> and using 32 bit integers on 64 bit windows is a bit odd.
> Anyway, hopefully that's not too off-topic.
> Best,

I agree, at least on python3 (the reason is that python 3, the subclass
thingy goes away, so it is less likely to break anything). I think we
could have a shot at this, it is quirky, but the current incosistency
is pretty bad too (and probably has a lot of bugs out in the wild,
because of tests on systems where long is 64bits).

A different issue though, though I wouldn't mind if someone ponders
this a bit more and maybe creates a pull request.

- Sebastian

> Ian Henriksen
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