FOR_DESCRIPTOR_ASSIGN (W*32, W*64)

Run-Time Subroutine: Creates an array descriptor in memory.

Module

USE IFCORE

Syntax

CALL FOR_DESCRIPTOR_ASSIGN (dp,base,size,reserved,rank,dims_info)

dp

(Input) A Fortran 95/90 pointer to an array; the array can be of any data type.

base

(Input) INTEGER(4) or INTEGER(8). The base address of the data being described by dp.

Note that a Fortran 95/90 pointer describes both the location and type of the data item.

size

(Input) INTEGER(4). The size of the data type; for example, 4 for INTEGER(4).

reserved

(Input) INTEGER(4). A logical bitwise OR combination of the following constants, which are defined in IFCORE.F90:

  • FOR_DESCRIPTOR_ARRAY_DEFINED - Specifies whether the array pointed to has been allocated or associated. If the bit is set, the array has been allocated or associated.

  • FOR_DESCRIPTOR_ARRAY_NODEALLOC - Specifies whether the array points to something that can be deallocated by a call to DEALLOCATE, or whether it points to something that cannot be deallocated. For example: integer, pointer :: p(:)
    integer, target :: t
    p => t ! t cannot be deallocated

    allocate(p(10)) ! t can be deallocated
    If the bit is set, the array cannot be deallocated.

  • FOR_DESCRIPTOR_ARRAY_CONTIGUOUS - Specifies whether the array pointed to is completely contiguous in memory or whether it is a slice that is not contiguous. If the bit is set, the array is contiguous.

rank

(Input) INTEGER(4). The rank of the array pointed to.

dims_info

(Input) An array of derived type FOR_DIMS_INFO; you must specify a rank for this array. The derived type FOR_DIMS_INFO is defined in IFCORE.F90 as follows:

TYPE FOR_DIMS_INFO

INTEGER(4) LOWERBOUND !Lower bound for the dimension

INTEGER(4) UPPERBOUND !Upper bound for the dimension

INTEGER(4) STRIDE !Stride for the dimension

END TYPE FOR_DIMS_INFO

The FOR_DESCRIPTOR_ASSIGN routine is similar to a Fortran 95/90 pointer assignment, but gives you more control over the assignment, allowing, for example, assignment to any location in memory.

You can also use this routine to create an array that can be used from both Fortran or C.

Example

use IFCORE

common/c_array/ array

real(8) array(5,5)

external init_array

external c_print_array

real(8),pointer :: p_array(:,:)

type(FOR_DIMS_INFO) dims_info(2)

call init_array()

do i=1,5

do j=1,5

print *,i,j, array(i,j)

end do

end do

dims_info(1)%LOWERBOUND = 11

dims_info(1)%UPPERBOUND = 15

dims_info(1)%STRIDE = 1

dims_info(2)%LOWERBOUND = -5

dims_info(2)%UPPERBOUND = -1

dims_info(2)%STRIDE = 1

call FOR_DESCRIPTOR_ASSIGN(p_array, &

LOC(array), &

SIZEOF(array(1,1)), &

FOR_DESCRIPTOR_ARRAY_DEFINED .or. &

FOR_DESCRIPTOR_ARRAY_NODEALLOC .or. &

FOR_DESCRIPTOR_ARRAY_CONTIGUOUS, &

2, &

dims_info )

p_array = p_array + 1

call c_print_array()

end

The following shows the C program containing init_array and c_print_array:

#include <stdio.h>

#if !defined(_WIN32) && !defined(_WIN64)

#define C_ARRAY c_array_

#define INIT_ARRAY init_array_

#define C_PRINT_ARRAY c_print_array_

#endif

double C_ARRAY[5][5];

void INIT_ARRAY(void);

void C_PRINT_ARRAY(void);

void INIT_ARRAY(void)

{

int i,j;

for(i=0;i<5;i++)

for(j=0;j<5;j++)

C_ARRAY[i][j] = j + 10*i;

}

void C_PRINT_ARRAY(void)

{

int i,j;

for(i=0;i<5;i++){

for(j=0;j<5;j++)

printf("%f ", C_ARRAY[i][j]);

printf("\n");

}

}

See Also