Re: Add softplus implementation in scipy.special

On 4/13/23, Warren Weckesser <[email protected]> wrote:
> On 4/13/23, Robert Kern <[email protected]> wrote:
>> +1 on adding `softplus()`.
>>
>> I would not worry about reading StackOverflow in this case. Our general
>> rule of thumb is that the minimum copyrightable segment of code is about
>> 10
>> lines. Everything about softplus is smaller than that. And we would not
>> be
>> copying the code straight in, in any case. We'll want a ufunc, I think.
>>
>
> For anyone reading the mailing list but not following the github
> issue: I added a comment
> (https://github.com/scipy/scipy/issues/17905#issuecomment-1507247170)
> that shows a simple option for computing `log1pexp(x)` (aka
> `softmax(x)`): use `np.logaddexp(0, x)`.

Oops, that should be `softplus(x)`, not `softmax(x)`.

WW

>
> Warren
>
>
>> On Thu, Apr 13, 2023 at 5:17 AM Pamphile Roy <[email protected]>
>> wrote:
>>
>>> Hi Aadya,
>>>
>>> Thank you for sending the email. This is in reference to the issue:
>>> https://github.com/scipy/scipy/issues/17905
>>>
>>> Note that we cannot use code from StackOverflow due to licensing
>>> incompatibilities. See here for more details
>>> https://scipy.github.io/devdocs/dev/hacking.html#license-considerations
>>>
>>> Cheers,
>>> Pamphile
>>>
>>>
>>> On 13.04.2023, at 10:28, [email protected] wrote:
>>>
>>> Hello Everyone,
>>> It might be nice to have a numerically stable softplus implementation,
>>> ie
>>> np.log1p(np.exp(x))
>>>
>>> This implementation can be based on the following stackoverflow answers
>>> :
>>>
>>> https://cs.stackexchange.com/questions/110798/numerically-stable-log1pexp-calculation
>>>
>>> https://stackoverflow.com/questions/44230635/avoid-overflow-with-softplus-function-in-python
>>>
>>> It can have a good place in the scipy module as it has other
>>> applications
>>> apart from ML/AI like it's a quite natural penalty function in
>>> optimization
>>> if one desires a smooth penalty in some optimization problems.
>>>
>>> All opinions are welcome. Let's discuss this?
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>>>
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>>
>>
>> --
>> Robert Kern
>>
>
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