Re: [f2py] "natural" Fortran calling conventions?

> I don't want my Fortran subroutine to have intent(c); if I did that,
> I'd have to write an intent(c) wrapper for every Fortran routine I
> want to call, which defeats the purpose.  Or if I write Fortran code
> optimized for intent(c), it won't be idiomatic Fortran and hard to
> maintain.

You don't have to write a whole wrapper to do this, you can use the
commenting method:

subroutine f2py_trsps_f(n,m,l,h)
!f2py intent(c) h
  implicit none
  integer :: n,m,l
  real*8  :: h(n,m,l)
  print*,h(1:8,1,1)
  return
end subroutine f2py_trsps_f

If you f2py this with "f2py -c f2py_trsps_f.f90" (and as far as I know
the same thing should work with fortran 77), you'll note that

<<< import time,f2py_trsps_f
<<< l,n,m=2**10,2**6,2**6
<<< h=arange(l*n*m).reshape([l,n,m])
<<< st=time.time();f2py_trsps_f.f2py_trsps_f(h);print 'c-order=',time.time()-st
   0.0000000000000000        1.0000000000000000
2.0000000000000000        3.0000000000000000        4.0000000000000000
       5.0000000000000000        6.0000000000000000
7.0000000000000000
c-order= 0.0583457946777
<<< h=asfortranarray(h)
<<< st=time.time();f2py_trsps_f.f2py_trsps_f(h);print 'f-order=',time.time()-st
   0.0000000000000000        1.0000000000000000
2.0000000000000000        3.0000000000000000        4.0000000000000000
       5.0000000000000000        6.0000000000000000
7.0000000000000000
f-order= 0.225140094757

That is, things work as expected (and more efficiently) if you give it
a python-natual c-order array. I agree that getting this behaviour
from "inent(c)" is a little counter-intuitive, but I think its the
closest thing to what you're looking for.

Once you get into the Fortran subroutine everything works normally.
You can forget that python or c was even involved once you get past
the f2py comment which the compiler doesn't see anyway. So no, I
wouldn't say this is idiomatic Fortran.

> And I'd like that with an error message if it can't be done
> efficiently
As far as I know, this can't currently be done, but I would say it's a
good idea.

Kevin