[Numpy-discussion] PR to add an initializer kwarg to ufunc.reduce (and similar functions)

[Sebastian Berg]

Initializer or this sounds fine to me. As an other data point which I
think has been mentioned before, `sum` uses start and min/max use
default. `start` does not work, unless we also change the code to
always use the identity if given (currently that is not the case), in
which case it might be nice. However, "start" seems a bit like solving
a different issue in any case.

Anyway, mostly noise. I really like adding this, the only thing worth
discussing a bit is the name :).

- Sebastian


On Mon, 2018-03-26 at 05:57 -0400, Hameer Abbasi wrote:
> It calls it `initializer` - See https://docs.python.org/3.5/library/f
> unctools.html#functools.reduce
> 
> Sent from Astro for Mac
> 
> > On Mar 26, 2018 at 09:54, Eric Wieser <wieser.eric+numpy at gmail.com>
> > wrote:
> > 
> > It turns out I mispoke - functools.reduce calls the argument
> > `initial`
> > 
> > On Mon, 26 Mar 2018 at 00:17 Stephan Hoyer <shoyer at gmail.com>
> > wrote:
> > > This looks like a very logical addition to the reduce interface.
> > > It has my support!
> > > 
> > > I would have preferred the more descriptive name "initial_value",
> > > but consistency with functools.reduce makes a compelling case for
> > > "initializer".
> > > 
> > > On Sun, Mar 25, 2018 at 1:15 PM Eric Wieser <wieser.eric+numpy at gm
> > > ail.com> wrote:
> > > > To reiterate my comments in the issue - I'm in favor of this.
> > > > 
> > > > It seems seem especially valuable for identity-less functions
> > > > (`min`, `max`, `lcm`), and the argument name is consistent with
> > > > `functools.reduce`. too.
> > > > 
> > > > The only argument I can see against merging this would be
> > > > `kwarg`-creep of `reduce`, and I think this has enough use
> > > > cases to justify that.
> > > > 
> > > > I'd like to merge in a few days, if no one else has any
> > > > opinions.
> > > > 
> > > > Eric
> > > > 
> > > > On Fri, 16 Mar 2018 at 10:13 Hameer Abbasi <einstein.edison at gma
> > > > il.com> wrote:
> > > > > Hello, everyone. I’ve submitted a PR to add a initializer
> > > > > kwarg to ufunc.reduce. This is useful in a few cases, e.g.,
> > > > > it allows one to supply a “default” value for identity-less
> > > > > ufunc reductions, and specify an initial value for reductions
> > > > > such as sum (other than zero.)
> > > > > 
> > > > > Please feel free to review or leave feedback, (although I
> > > > > think Eric and Marten have picked it apart pretty well).
> > > > > 
> > > > > https://github.com/numpy/numpy/pull/10635
> > > > > 
> > > > > Thanks,
> > > > > 
> > > > > Hameer
> > > > > Sent from Astro for Mac
> > > > > 
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