[Numpy-discussion] Do not understand what f2py is reporting

[Andras Deak]

On Sun, Nov 1, 2020 at 2:33 AM Samuel Dupree <sdupree at speakeasy.net> wrote:
>
> I'm attempting to build wrappers around two Fortran routines. One is a
> Fortran 77 subroutine (see file gravity_derivs.f) that calls a Fortran
> 90 package that performs automatic differentiation (see file
> auto_deriv.f90).
>
> I'm running he Anaconda distribution for Python 3.7.6 on a Mac Pro
> (2019) under Mac OS X Catalina (ver. 10.15.6). The version of NumPy I'm
> running is 1.18.3. The commands I used to attempt the build are
> contained in the file auto_deriv_build. The messages output by f2py are
> captured in the file auto_derivs_build_report.txt.
>
> I don't understand the cause behind the error messages I got, so any
> advice would be welcomed.
>
> Sam Dupree.

Hi Sam,

I've got a partial solution.
I haven't used f2py yet but at least the error from your first `f2py`
call seems straightforward. Near the top:

    Line #119 in gravity_derivs.f:"      integer * 4            degree"
        updatevars: no name pattern found for entity='*4degree'. Skipping.

This shows that the fortran code gets parsed as `(integer)
(*4degree)`. That can't be right. There might be a way to tell f2py to
do this right, but anyway I could make your code compile by replacing
every such declaration with `integer * 4 :: degree` etc (i.e. adding
double colons everywhere).
Once that's fixed your first f2py call raises another error:

    Fatal Error: Cannot open module file ‘deriv_class.mod’ for reading
at (1): No such file or directory

I could generate these mod files by manually running `gfortran -c
auto_deriv.f90`. After that the .mod files appear and your first
`f2py` call will succed.
You can now `import gravity_derivs`, but of course this will lead to
an error because `auto_deriv` is not available in python.
Unfortunately your _second_` f2py` call also dies on `auto_deriv.f90`,
with such offending lines:

    In: :auto_deriv:auto_deriv.f90:ad_auxiliary
    get_parameters: got "invalid syntax (<string>, line 1)" on '(/((i,
i=j,n), j=1,n)/)'

I'm guessing that again f2py can't parse that syntax.
My hunch is that if you can get f2py to work with `auto_deriv.f90` you
should first run that. This should hopefully generate the .mod files
after which the second call to `f2py` with `gravity_derivs.f` should
work. If `f2py` doesn't generate the .mod files you could at worst run
your fortran compiler yourself between the two calls to `f2py`.
Cheers,

András

> _______________________________________________
> NumPy-Discussion mailing list
> NumPy-Discussion at python.org
> https://mail.python.org/mailman/listinfo/numpy-discussion