numpy-discussion

[Numpy-discussion] accessing FORTRAN from Python

[Christian M. <mee...@un...>]

Hoi,

thanks to Robert Kern who helped me out yesterday on the f2py-list, I was able 
to make some progress in accessing FORTRAN from Python. But only some 
progress ...

If I have the following code, named 'hello.f':
C File hello.f
      subroutine foo (a)
      integer a
      print*, "Hello from Fortran!"
      print*, "a=",a
      end

and compile it with g77 -shared -fPIC hello.f -o hello.so

and then start python, I get the following:
>>> from numpy import *
>>> from ctypes import c_int,  POINTER, byref
>>> hellolib = ctypeslib.load_library('hello', '.')
>>> hello = hellolib.foo_
>>> hello(42)
 Hello from Fortran!
Segmentation fault

Can anybody tell me where my mistake is? (Currently python 2.4.1 (no intention 
to update soon), the most recent ctypes, and numpy '1.0.dev3341' from svn.)

And a second question: Are there simple examples around which show how to pass 
and retrieve lists, numpy arrays, and dicts to and from FORTRAN? Despite an 
intensive web search I couldn't find anything.

TIA
Christian

Re: [Numpy-discussion] accessing FORTRAN from Python

[Robert K. <rob...@gm...>]

Christian Meesters wrote:
> Hoi,
> 
> thanks to Robert Kern who helped me out yesterday on the f2py-list, I was able 
> to make some progress in accessing FORTRAN from Python. But only some 
> progress ...
> 
> If I have the following code, named 'hello.f':
> C File hello.f
>       subroutine foo (a)
>       integer a
>       print*, "Hello from Fortran!"
>       print*, "a=",a
>       end
> 
> and compile it with g77 -shared -fPIC hello.f -o hello.so
> 
> and then start python, I get the following:
>>>> from numpy import *
>>>> from ctypes import c_int,  POINTER, byref
>>>> hellolib = ctypeslib.load_library('hello', '.')
>>>> hello = hellolib.foo_
>>>> hello(42)
>  Hello from Fortran!
> Segmentation fault
> 
> Can anybody tell me where my mistake is? (Currently python 2.4.1 (no intention 
> to update soon), the most recent ctypes, and numpy '1.0.dev3341' from svn.)
> 
> And a second question: Are there simple examples around which show how to pass 
> and retrieve lists, numpy arrays, and dicts to and from FORTRAN? Despite an 
> intensive web search I couldn't find anything.

I don't believe anyone has posted anything about calling FORTRAN code using
ctypes. Why aren't you using f2py?

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
 that is made terrible by our own mad attempt to interpret it as though it had
 an underlying truth."
  -- Umberto Eco

Re: [Numpy-discussion] accessing FORTRAN from Python

[Christian M. <mee...@un...>]

On Tuesday 14 November 2006 18:01, Robert Kern wrote:
>
> I don't believe anyone has posted anything about calling FORTRAN code using
> ctypes. Why aren't you using f2py?
What if we just forget about my last post? (I guess I was doing way too many 
things in parallel, stumbled across the g95 site and tried to apply what's 
posted there in the way described there ...)

Sorry for this confusion and thanks, Robert, that again you brought me back on 
track, things are working now.

Christian

Re: [Numpy-discussion] accessing FORTRAN from Python

[Hanno K. <kl...@ph...>]

Hi Christian,

I send this off-list as there are probably a lot more knowledgeable  
people around there.

However, I don't entirely understand your problem (I'm not on the f2py  
list).

What happens if you try:

C file hello.f
       subroutine foo(a)
       integer a
Cf2py intent(in) a
       print*, "Hello from  Fortran!"
       print*, "a=",a
       end


f2py -m -c hello hello.f

That usually did the trick for me. What are your error messages, if you  
try the above?

Best regards,
Hanno


On Nov 14, 2006, at 12:09 PM, Christian Meesters wrote:

> Hoi,
>
> thanks to Robert Kern who helped me out yesterday on the f2py-list, I  
> was able
> to make some progress in accessing FORTRAN from Python. But only some
> progress ...
>
> If I have the following code, named 'hello.f':
> C File hello.f
>       subroutine foo (a)
>       integer a
>       print*, "Hello from Fortran!"
>       print*, "a=",a
>       end
>
> and compile it with g77 -shared -fPIC hello.f -o hello.so
>
> and then start python, I get the following:
>>>> from numpy import *
>>>> from ctypes import c_int,  POINTER, byref
>>>> hellolib = ctypeslib.load_library('hello', '.')
>>>> hello = hellolib.foo_
>>>> hello(42)
>  Hello from Fortran!
> Segmentation fault
>
> Can anybody tell me where my mistake is? (Currently python 2.4.1 (no  
> intention
> to update soon), the most recent ctypes, and numpy '1.0.dev3341' from  
> svn.)
>
> And a second question: Are there simple examples around which show how  
> to pass
> and retrieve lists, numpy arrays, and dicts to and from FORTRAN?  
> Despite an
> intensive web search I couldn't find anything.
>
> TIA
> Christian
>
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-- 
Hanno Klemm							kl...@it...
ETH Zurich 							tel: +41-1-6332580
Institute for theoretical physics	mobile: +41-79-4500428
									http://www.mth.kcl.ac.uk/~klemm