[SciPy-Dev] FFTLog

[Jacob Vanderplas]

Hi Dieter,
That's very cool! Before discussion of whether this fits into SciPy,
there's one issue: I don't see any license on the Fortran code. This means,
unfortunately, that it defaults to some form of "all-rights-reserved" and
cannot be used in SciPy.

Often it's enough to email the package author, link to some information
like my post at [1], and request that they add a BSD-style license to their
code (note that a GPL-style license would make it unusable by SciPy).

Though we may want to see what others think about including this in SciPy
before going too far down that route. For what it's worth, I'd suggest
starting by making sure your Python wrapper is well-documented &
well-tested; if it proves useful to many people, it would then be quite
easy to pull into SciPy.

   Jake

[1]
http://www.astrobetter.com/blog/2014/03/10/the-whys-and-hows-of-licensing-scientific-code/

 Jake VanderPlas
 Senior Data Science Fellow
 Director of Research in Physical Sciences
 University of Washington eScience Institute

On Thu, Oct 6, 2016 at 7:20 PM, Dieter Werthmüller <dieter at werthmuller.org>
wrote:

> Dear SciPy-devs,
>
> I recently had the need for a logarithmic FFT routine, and did a quick
> f2py around Andrew Hamilton's FFTLog:
>   http://casa.colorado.edu/~ajsh/FFTLog
>
> I put my f2py-setup and my pyf-file up on GitHub:
>   https://github.com/prisae/fftlog
>
> I thought it might be a useful addition to the SciPy FFTPack. Specifically
> as three out of the five fortran-files, of which FFTLog consists, are
> already in scipy/fftpack.
>
> I have never contributed to SciPy and therefore do not know how much work
> it would involve to get it into SciPy. However, I thought I ask. If there
> is interest I expect that it would not take long for an experienced person,
> as it is a fairly small addition. Or someone could point me to the right
> direction on what to do to get it in.
>
>
> I append some comments on the involved files of FFTLog and some comments
> regarding their licenses. I believe it is compatible with SciPy.
>
> Thanks for all your good work!
> Dieter
>
>
> Files and Licenses/Permissions
> ------------------------------
>
> Files of FFTLog
>
>   [1] cdgamma.f
>   [2] drfftb.f
>   [3] drfftf.f
>   [4] drffti.f
>   [5] fftlog.f
>
> (plus a test routine, fftlogtest.f)
>
> -- [1] --
> The original FFTLog states about this file:
>
> FFTLog uses [...] and a modified version of the complex Gamma function
> from the gamerf package at momonga.t.u-tokyo.ac.jp/~ooura/gamerf.html.
> The original gamerf copyright statement states:
>
> Copyright(C) 1996 Takuya OOURA (email: ooura at mmm.t.u-tokyo.ac.jp).
> You may use, copy, modify this code for any purpose and
> without fee. You may distribute this ORIGINAL package.
>
> Permission to distribute the modified gamma function code with the FFTLog
> package has been granted (email from Takuya Ooura to Andrew Hamilton dated
> 16 March 1999).
>
> Hence I think it is compatible with SciPy, or am I wrong?
>
> Alternatively it could be replaced with scipy.special.loggamma, I think,
> but I do not know if it is possible to mix Fortran and Python code with
> f2py.
>
> -- [2], [3], [4] --
> They are from the NCAR suite of FFT routines (Swarztrauber 1979).
>
> As far as I can see they are already in SciPy, in
> scipy/fftpack/src/dfftpack/ (dfftb.f, dfftf.f, and dffti.f).
>
> So there is definitely not a licensing problem here.
>
> -- [5] --
> This is the actual FFTLog routine from Hamilton.
>
> I asked Hamilton for permission before publishing his source code at
> github.com/prisae/fftlog.
>
> His email response was:
>
> -- start email from 28/09/2016 --
>   Dieter,
>
>   You are welcome to use fftlog in any way you choose.  Please note the
>   credits commented in the code:
>
>   c FFTLog uses the NCAR suite of FFT routines,
>   c and a modified version of the complex Gamma function
>   c from the gamerf package at
>   c http://momonga.t.u-tokyo.ac.jp/~ooura/gamerf.html .
>   c The original gamerf copyright statement states:
>   c   Copyright(C) 1996 Takuya OOURA (email: ooura at mmm.t.u-tokyo.ac.jp).
>   c   You may use, copy, modify this code for any purpose and
>   c   without fee. You may distribute this ORIGINAL package.
>   c
>   c Permission to distribute the modified gamma function code
>   c with the FFTLog package has been granted
>   c (email from Takuya Ooura to Andrew Hamilton dated 16 March 1999).
>
>   Andrew
> -- end email from 28/09/2016 --
>
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