Passing 2d array from Fortran to C [duplicate]

问题

I am having difficulty passing a 2d array from Fortran to C function. However, after all the support the following code is functional 100%.

The following is my C function:

#include <stdio.h>
  void print2(void *p, int n)
  {
     printf("Array from C is \n");
     double *dptr;
     dptr = (double *)p;
     for (int i = 0; i < n; i++)
     {
        for (int j = 0; j<n; j++)
            printf("%.6g \t",dptr[i*n+j]);

        printf("\n");
     }
  }

The following is my Fortran code:

        program linkFwithC
        use iso_c_binding
        implicit none 
        interface
          subroutine my_routine(p,r) bind(c,name='print2')
            import :: c_ptr
            import :: c_int
            type(c_ptr), value :: p
            integer(c_int), value :: r
          end subroutine
        end interface


        integer,parameter ::n=3
        real (c_double), allocatable, target :: xyz(:,:)
        real (c_double), target :: abc(3,3)
        type(c_ptr) :: cptr
        allocate(xyz(n,n))
        cptr = c_loc(xyz(1,1))

        !Inputing array valyes

        xyz(1,1)= 1
        xyz(1,2)= 2
        xyz(1,3)= 3
        xyz(2,1)= 4
        xyz(2,2)= 5
        xyz(2,3)= 6
        xyz(3,1)= 7
        xyz(3,2)= 8
        xyz(3,3)= 9


        call my_routine(cptr,n)
        deallocate(xyz)
      pause
      end program linkFwithC

The code runs fine;however, the array elements in C need to be re-organized.

Note, In order to link the C function with the FORTRAN code in a visual studio environment, one should follow the following step:

Write the C function in static library project
build the .lib file
Create the FORTRAN project and write your code
Add the .lib file to the FORTRAN project(just add it to the sources file)
Compile and run.

Thanks, Anas

回答1:

There are two ways arrays like you are passing are stored - ROW-MAJOR and COLUMN-MAJOR. C uses row-major, fortran uses column-major.

You will have to access the array elements in C in the order as it was created in fortran.

Rather than post a code block, you might do better to understand it before you code it. See this for clarity: http://en.wikipedia.org/wiki/Row-major_order

来源：https://stackoverflow.com/questions/27584674/passing-2d-array-from-fortran-to-c

标签

arrays

fortran

fortran-iso-c-binding