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

[Hameer Abbasi]

 Actually, the behavior right now isn’t that of `default` but that of
`initializer` or `start`.

This was discussed further down in the PR but to reiterate: `np.sum([10],
initializer=5)` becomes `15`.

Also, `np.min([5], initializer=0)` becomes `0`, so it isn’t really the
default value, it’s the initial value among which the reduction is
performed.

This was the reason to call it initializer in the first place. I like
`initial` and `initial_value` as well, and `start` also makes sense but
isn’t descriptive enough.

Hameer
Sent from Astro <https://www.helloastro.com> for Mac

On Mar 26, 2018 at 12:06, Sebastian Berg <sebastian at sipsolutions.net> wrote:


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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