Dieter,

First, a warning: this is going to involve some fun. ;-) Before going too far you should probably check that the different versions of the complex Gamma functions use the same branch cuts, etc. Note that if you want this to work in your external git repo you'll need to build against scipy master.

Steps should be roughly:
-- Write a Cython script that wraps the Cython version of SciPy's loggamma. See

https://scipy.github.io/devdocs/special.cython_special.html#module-scipy.special.cython_special

for info on cimporting loggamma.
-- Export the wrapper as a C function using these steps:

http://docs.cython.org/en/latest/src/userguide/external_C_code.html#using-cython-declarations-from-c

-- Add the Cythonized C file to your setup and add an Interface block to your Fortran code letting it know how to call the C function.

On Sat, Oct 8, 2016 at 1:11 PM, Dieter Werthmüller <dieter@werthmuller.org> wrote:
Joshua

Thanks for your input. How could I include the Cython loggamma function within my setup script, so that fftlog.f would pick it up?

Adjusting fftlog.f to pick up dfft*.f from scipy/fftpack/src/dfftpack worked without problems. So if I could do the same for loggamma, then the only new file would be fftlog.f, for which we have the permission.

Thanks,
Dieter


On 07/10/16 21:18, Joshua Wilson wrote:
Re log gamma: under the hood the SciPy versions are in C (real version)
and Cython (complex version), so linking them up with Fortran code is
definitely doable.

On Fri, Oct 7, 2016 at 8:16 PM, Ralf Gommers <ralf.gommers@gmail.com
<mailto:ralf.gommers@gmail.com>> wrote:



    On Sat, Oct 8, 2016 at 1:58 PM, Dieter Werthmüller
    <dieter@werthmuller.org <mailto:dieter@werthmuller.org>> wrote:

        Evening,

        I wrote to Andrew Hamilton, and below is his answer. He has
        basically no problem with it at all, I just don't know if his
        response is explicit enough.

        I think my email was quite extensive, and I assume that is as
        much as we will get from him. I also do not expect him to change
        his on "13 Mar 1999, 21:17" from TeX translated website...

        What do you think, is this enough?


    Yes, that's perfectly fine. Thanks for clarifying that Dieter.

    Cheers,
    Ralf


        I also wrote to Takuya Ooura, and will let you know of his
        response, if I get one. However, as there are other complex
        logarithmic double precision gamma functions around, one already
        in scipy, this piece is not mission critical.

        Regards,
        Dieter

        ========== START email correspondence with Andrew Hamilton
        ==========
        Subject: Re: FFTLog - license
        From: Andrew Hamilton <andrew.hamilton@colorado.edu
        <mailto:andrew.hamilton@colorado.edu>>
        Date: 07/10/16 18:22
        To: Dieter Werthmüller <dieter.werthmuller@gmx.ch
        <mailto:dieter.werthmuller@gmx.ch>>
        CC: Andrew.Hamilton@colorado.edu
        <mailto:Andrew.Hamilton@colorado.edu>


        Dieter,

        I approve your adding the license language you suggest to
        FFTLog, and making available the resulting package for distribution.

        Andrew

        On 10/07/2016 03:42 PM, Dieter Werthmüller wrote:
        > Dear Andrew,
        >
        > Please apologize me bothering you again.
        >
        > After I published the code to wrap your FFTLog for Python I
        thought that
        > it would be much better if your FFTLog would make it straight
        into the
        > scientific library of Python. This would make your FFTLog
        available to a
        > much wider audience.
        >
        > I contacted the developers of SciPy (http://scipy.org), and
        they are
        > interested in including your code. However, there is one issue:
        > licensing. Code that is published on the web without a license
        file is
        > copyrighted under law, and SciPy can for this reason not
        include your
        > code into their library.
        >
        > All I ask for is if you could confirm to us by email that we
        are allowed
        > to distribute your FFTLog under the BSD-3-Clause license:
        > https://opensource.org/licenses/BSD-3-Clause
        <https://opensource.org/licenses/BSD-3-Clause>
        >
        > The license is just a suggestion, any other BSD or MIT compatible
        > license would be fine as well. (For the same, legal reasons we
        recommend
        > to publish a license file on your website too, but that is
        obviously
        > entirely up to you. It might, however, clarify things for
        future visitors.)
        >
        > It would only affect your fftlog.f file, and the changes you
        made to
        > cdgamma.f. I will write Takuya OOURA as well regarding the
        original
        > cdgamma.f-file, asking him the same favour. And the three
        drfft*.f are
        > already in the SciPy-library with the whole FFTPack.
        >
        > If you are interested why this issue arises, Jake Vanderplas,
        one of the
        > developers of SciPy, wrote an interesting article about the topic:
        >
        http://www.astrobetter.com/blog/2014/03/10/the-whys-and-hows-of-licensing-scientific-code/
        <http://www.astrobetter.com/blog/2014/03/10/the-whys-and-hows-of-licensing-scientific-code/>
        >
        > Thank you again for your time and for making FFTLog available!
        > Best regards,
        > Dieter
        >
        ========== END email correspondence with Andrew Hamilton ==========

        On 07/10/16 15:13, Ralf Gommers wrote:



            On Sat, Oct 8, 2016 at 9:11 AM, Ralf Gommers
            <ralf.gommers@gmail.com <mailto:ralf.gommers@gmail.com>
            <mailto:ralf.gommers@gmail.com
            <mailto:ralf.gommers@gmail.com>>> wrote:



                On Sat, Oct 8, 2016 at 8:59 AM, Dieter Werthmüller
                <dieter@werthmuller.org <mailto:dieter@werthmuller.org>
            <mailto:dieter@werthmuller.org
            <mailto:dieter@werthmuller.org>>> wrote:

                    Jake,

                    Thanks for the clarification. I will try to get the
            permissions
                    from the
                    authors.

                    What is regarded as sufficient? Is an email from the
            author,
                    granting
                    me/SciPy to distribute their code with a specific,
            BSD-style license
                    sufficient? Or do they necessarily have to change
            the websites where
                    they host the code to include the license?


                An email stating that the code can be distributed under
            a BSD
                license  (or MIT or other compatible license) is enough.


            Some delay on the line, missed Jake's answer. Email is
            enough, but a
            change in the repo would of course be even better.

            Ralf




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