| Re: Help on calling Fortran routines from IDL under linux [message #36583] |
Wed, 08 October 2003 05:38  |
Nigel Wade
Messages: 286
Registered: March 1998
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Senior Member |
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David Green wrote:
> For the past few days i have been trying to call basic fortran
> routines from IDL (IDL 6.0 and Gentoo Linux on a PC). First i tried
> using the CALL_EXTERNAL approach using both fortran and C wrappers as
> shown in the IDL documentation however the output i was getting from
> the sum_array example was incorrect. Here is what i did first:
>
> ------------------------------------------------------------ ---------
> test_call_external.pro - the IDL calling routine
> ------------------------------------------------------------ ---------
> pro test_call_external
>
> x = [1.0,2.0,3.0]
> sum = 0.0
> n = n_elements(x)
> s = call_external('/home/david/PhD/Fortran/sum_array.so',
> 'sum_array', $
> x, n, sum)
> print, s
> help, s
>
> end
>
> ------------------------------------------------------------ ---------
> sum_array.c - the C wrapper as in the IDL documentation
> ------------------------------------------------------------ ---------
> #include <stdio.h>
>
> void sum_array(int argc, void *argv[])
> {
> extern void sumd_(); /* Fortran Routine */
> int *n;
> float *s, *f;
>
> f = (float *) argv[0]; /* Array pntr */
> n = (int *) argv[1]; /* Get # of elements */
> s = (float *) argv[2]; /* Pass back result a parameter */
>
> sumd_(f, n, s); /* Compute Sum */
> }
>
> ------------------------------------------------------------ ---------
> sumd.f - the Fortran routine as in the documentation
> ------------------------------------------------------------ ---------
> SUBROUTINE sumd(array, n, sum)
> INTEGER*4 n
> REAL*4 array(n), sum
>
> sum=0.0
> DO i=1,n
> sum = sum + array(i)
> ENDDO
>
> RETURN
> END
>
>
> I compiled both the sumd.f and sum_array.c files to objects then
> linked them together into a shared object (sum_array.so) using gcc (i
> think, i'm a gcc ultra newbie) as follows:
>
> gcc -c sumd.f
> gcc -c sum_array.c
> gcc -shared -o sum_array.so sumd.o sum_array.o
>
> However, when i compile and run test_call_external i get the output:
>
> -1073746820
> S LONG = -1073746820
>
> This, i don't understand, so i figured i'd try the fortran wrapper
> like this...
>
> ------------------------------------------------------------ ---------
> dave.f - the Fortran routine as in the documentation
> ------------------------------------------------------------ ---------
> SUBROUTINE SUM_ARRAY(argc, argv) !Called by IDL
> INTEGER*4 argc, argv(*) !Argc and Argv are integers
>
> j = LOC(argc) !Obtains the number of arguments (argc)
> !Because argc is passed by VALUE.
>
> CALL SUM_ARRAY1(%VAL(argv(1)), %VAL(argv(2)), %VAL(argv(3)))
> RETURN
> END
>
> SUBROUTINE SUM_ARRAY1(array, n, sum)
> INTEGER*4 n, test
> REAL*4 array(n), sum
>
> sum=0.0
> DO i=1,n
> sum = sum + array(i)
>
> ENDDO
> RETURN
> END
>
> I compiled this with gcc as (to get the shared object dave.so)
>
> gcc -w -shared -o dave.so dave.f
>
> and then run the following idl program...
>
> ------------------------------------------------------------ ---------
> test_call_external2.pro - idl calling routine
> ------------------------------------------------------------ ---------
> pro test_call_external
>
> x = [1.0,2.0,3.0]
> sum = 0.0
> n = n_elements(x)
> s = call_external('/home/david/PhD/Fortran/dave.so', 'sum_array__', $
> x, n, sum)
> print, s
> help, s
>
> end
Hmm, shouldn't that be 'print, sum'? Your C wrapper puts the sum in the 3rd
parameter, argv[2].
Also, your C wrapper return type is void, so s in IDL will have no value.
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| Re: Help on calling Fortran routines from IDL under linux [message #36668 is a reply to message #36583] |
Thu, 09 October 2003 02:09  |
isoaga2
Messages: 4
Registered: October 2003
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Junior Member |
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Nigel Wade <nmw@ion.le.ac.uk> wrote in message news:<bm10fa$ef8$1@south.jnrs.ja.net>...
>
>
> Hmm, shouldn't that be 'print, sum'? Your C wrapper puts the sum in the 3rd
> parameter, argv[2].
>
> Also, your C wrapper return type is void, so s in IDL will have no value.
Hey thanx Nigel, you are right of course, i thouhgt that the s
variable would contain the answer however this is obviously not the
case, do you know what it does contain?
Using the fortran wrapper works fine and print, sum gives the correct
answer. Now to apply this approach to a more complicated function...
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