[f2py] "natural" Fortran calling conventions?
pearu.peterson at gmail.com
Thu Oct 15 10:43:03 EEST 2009
Thomas Breuel wrote:
>> 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)
>> end subroutine f2py_trsps_f
> OK, I tried this and it isn't working for me. intent(c) seems to
> instruct Python to pass the data in C order, but Fortran doesn't seem
> to know that, so the elements end up in the wrong order.
Could you send a simple example demonstrating the problem?
> Furthermore, f2py seems to generate some kind of array bounds checking
> code so that I can't interchange the array bounds in the Fortran code.
> intent(cache) also isn't doing the trick.
In case it would help, you can disable checks by specifying `check()`
for the corresponding variable:
!f2py check() h
> Even if they did, the meaning of intent(c) and intent(cache) when used
> in this way could change any release (and likely will once f2py
> supports new Fortran arrays).
> Altogether, I still think f2py should get an "intent(natural)"; with
> that, a C array declared as:
> float a;
> would get passed to Fortran as:
> subroutine f(a)
> !f2py intent(natural) a
> real, intent(in) :: a(3,99,17)
> end subroutine f
> This would let me write natural, efficient Fortran loops that
> correspond to the natural, efficient C loops, and it would mean that
> there is no cost in calling from Python to Fortran and back.
I'll keep this in mind when I get a chance to work with f2py..
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