BUG: special: algorithmic Error in `ratevl` in `cephes/polevl.h`

[ZhibingSun]

BUG: special: algorithmic Error in `ratevl` in `cephes/polevl.h`

[ZhibingSun]

Hi, I have updated my post as required, and thanks for letting me know that I can enclose equations and use LaTex. Please let me know if I need to provide more information.

[fancidev]

I followed Contributor quickstart guide and run command upto python3 dev.py test, but it gives me error meson.build:84:0: ERROR: Compiler gfortran cannot compile programs.

I use Mac M1 and had the same error message. I worked around it by executing the following before python dev.py build:

export LIBRARY_PATH="$LIBRARY_PATH:/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib"

This works for me because after I upgraded XCode, some of the environment variables are not correctly set.

Btw, after the config error message, there should be somewhere that shows you a detailed error log. In that log it explains exactly why it “couldn’t compile Fortran program”. For me it was unable to “-lSystem”.

@ZhibingSun

[lucascolley]

Hi @ZhibingSun , as a small ask, could you edit your post to enclose equations in backticks (this symbol `)? That should make it easier to read! (Or you can use $ signs for LaTeX too).

cc @steppi

[steppi]

Thanks for the bug report @ZhibingSun! It looks like this error goes back to when this function was first introduced. It seems no one noticed before you because ratevl is only used in one place in SciPy and in that case the numerator and denominator have the same degree.

scipy/scipy/special/special/cephes/lanczos.h

Line 83 in 3559245

SPECFUN_HOST_DEVICE double lanczos_sum(double x) { return ratevl(x, lanczos_num, 12, lanczos_denom, 12); }

Would you like submit a pull request with the fix?

[ZhibingSun]

Yes, I would love to contribute. Could you give me some guidance of how to submit a pull request?

[steppi]

Yes, I would love to contribute. Could you give me some guidance of how to submit a pull request?

Great! Start with the Contributor quickstart in the Developer documentation, and then check out the Development workflow section. That should be enough to get started.

[ZhibingSun]

I followed Contributor quickstart guide and run command upto python3 dev.py test, but it gives me error meson.build:84:0: ERROR: Compiler gfortran cannot compile programs. I checked that gfortran exists on my system M1 mac by running gfortran --version, which gives me NU Fortran (GCC) 12.2.0 Copyright (C) 2022 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Could you tell me how I shall proceed?

[andyfaff]

Are you on windows or Linux? I suggesting trying to compile a really simple test program (c.f. hello world) to see if the compiler actually works.

[ZhibingSun]

I am on M1 mac Ventura 13.6.6.

[andyfaff]

How did you install gfortran? I've found homebrew to work.

[ZhibingSun]

I installed it from here. https://github.com/fxcoudert/gfortran-for-macOS/releases. As I mentioned in my previous post, I ran gfortran --version and it works.

[andyfaff]

Running that command doesn't necessarily mean that the compiler works. Try compiling and running a test program.

[lucascolley]

These two lines from http://scipy.github.io/devdocs/building/index.html#system-level-dependencies were enough for me.