[Numpy-discussion] Binary ufuncs: minimum
Charles R Harris
Tue May 27 16:54:37 CDT 2008
On Tue, May 27, 2008 at 3:28 PM, Charles R Harris <email@example.com>
> On Tue, May 27, 2008 at 2:40 PM, Travis E. Oliphant <
> firstname.lastname@example.org> wrote:
>> Charles R Harris wrote:
>> > On Tue, May 27, 2008 at 2:10 PM, Travis E. Oliphant
>> > <email@example.com <mailto:firstname.lastname@example.org>> wrote:
>> > Stéfan van der Walt wrote:
>> > > Did this change recently?
>> > >
>> > > In : np.__version__
>> > > Out: '1.1.0.dev5211'
>> > >
>> > > In : np.minimum(np.uint8(164), np.uint64(12807)).dtype
>> > > Out: dtype('uint64')
>> > >
>> > > But yes, that looks like it should return a uint8.
>> > >
>> > This discussion is really moot unless a proposal for how to handle
>> > different casting rules for different ufuncs is proposed. Right
>> > the type-promotion rules are generic and do not depend on the
>> > ufunc only
>> > on coercion rules for the mixed types.
>> > One problem with a casting-rules-per-ufunc approach is that it
>> > makes it
>> > harder to add new types and have them fit in to the casting
>> > (which is currently possible now). Some mechanism for allowing the
>> > types to plug-in to the per-ufunc rules would be needed.
>> > These are not impossible things, just a bit of work and not on my
>> > personal priority list.
>> > Not everything follows those rules, however. So I have put these
>> > things up for review so that we can agree on what the are. Of
>> > particular concern in my mind are the bitwise and shift operators
>> > which currently work in a counter intuitive manner.
>> Right now, the only complete description of the rules is the code that
>> implements them. So, from that perspective, yes everything follows
>> those rules ;-)
> So the segfaults are defined behavior? ;) It's like pulling teeth without
> anesthesia to get these things defined and everyone is going to think I'm an
> a-hole. It's a dirty job, but someone has got to do it.
> What about abs(-128) returning a negative number for int8? Might it not be
> better to return the corresponding unsigned type? Can't check that at the
> moment, as I'm trying to get 64 bit Ubuntu installed on a software raid1
> partition for further checks, and Ubuntu overwrote my MBR without asking.
> It's a traditional Ubuntu thing.
Yep, abs fails:
In : abs(array([-128,-128], dtype=int8))
Out: array([-128, -128], dtype=int8)
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