Offloading 2d arrays in C/C++ using pragmas - problems

[james_B_8]

I'm trying to offload a dynamically allocated 2d array of floats. I can't seem to get it to work however. My code is this:

[cpp]
#include <stdio.h>
#include <stdlib.h>

float **alloc_2d(int rows, int cols);
void dealloc_2d(float **array, int rows);

int main()
{
    /* array size */
    const int d1 = 10;
    const int d2 = 10;

    /* malloc some 2d c arrays */
    float **x;
    x = alloc_2d(d1,d2);

    /* assign some values to them */
    int i,j;
    for (i=0; i<d1; i++)
        for (j=0; j<d2; j++)
        {
            x = i*j;
        }

    printf("x[0][0] = %f\n", x[0][0]);

    /* offload to the mic and check value there */
#pragma offload target(mic:0) in( x[0:d1][0:d2] : alloc( x[0:d1][0:d2] ) )
    {
        printf("x[0][0] = %f\n", x[0][0]);
    }

    dealloc_2d(x, d1);

    return 0;
}

float **alloc_2d(int rows, int cols)
{
    float **array;
    array = malloc( rows * sizeof *array );
    int i;
    for (i=0; i<rows; i++)
        array = malloc( cols * sizeof *array );

    return array;
}

void dealloc_2d(float **array, int rows)
{
    int i;
    for (i=0; i<rows; i++)
        free(array);
    free(array);
}

[/cpp]

I compile with icc main.c and I get the error:

": internal error: backend signals

compilation aborted for main.c (code 4)

What's the correct way to offload multidimensional arrays in C/C++? Would it be wiser to just store my data as a 1D array and compute the memory locations manually?

[Frances_R_Intel]

James B. wrote:

What's the correct way to offload multidimensional arrays in C/C++? Would it be wiser to just store my data as a 1D array and compute the memory locations manually?

Yes. You cannot offload a pointer to a point with a #pragma offload directive. The best solution is malloc a single block of memory and set up the pointers later. You will need an array of pointers on the host and a separate one on the coprocessor because the actual addresses will be different.

[james_B_8]

Good. Thanks for confirming that for me.