CODEWITHSUNDEEP
c++visual-studioopencl
dominicbri7
dominicbri7

Reputation: 2599

Pass unknown size multi-dimensional array to function

I need to write a program that computes values in a matrix, first sequentially, then in parallel using openCL.

It is the same thing as I already did in regular C (using MPI)

I want to make simple functions to initializeMatrix and printMatrix and the likes.

In C i used to do this very simply :

// Matrix initialization
 void initMatrix(size_t M, size_t N, double (*matrix)[M][N][2])
{
    int i, j;
    for (j = 0; j < N; ++j)
    {
        for (i = 0; i < M; ++i)
        {
            (*matrix)[i][j][0] = (double)(( i * ( M - i - 1 ) ) * ( j * ( N - j - 1 ) ));
            (*matrix)[i][j][1] = (*matrix)[i][j][0];
        }
    }
    printf("Matrix has been initialized\n");
}

I saw this gets me errors in C++, as the compiler wants to know at COMPILE TIME the sizes of arrays (the M and N sizes are passed as arguments to program, therefore I can't know at compile time).

How do I do this in C++?

I am considering using Vectors, but I'm not sure if it's a good idea since I will have to use the OpenCL library

Upvotes: 0

Views: 135

Answers (1)

vsoftco
vsoftco

Reputation: 56547

You can pass the array by reference/const reference via a template:

#include <iostream>
#include <cstddef> // for std::size_t

template <typename T, int M, int N, int P>
void f(T (&arr)[M][N][P]) // accepts 3-D arrays of arbitrary types
{
    std::cout << "Size: " << M << " x " << N << " x " << P;
}

int main()
{
    const std::size_t M = 2; 
    const std::size_t N = 3;
    double arr[M][N][4];
    f(arr);
}

Upvotes: 2

Related Questions