Summing up all elements of a buffer

I cant quite figure out the best way to sum up all the elements of buffer.

I have tried the following kernels but neither sums up the buffers properly.

__kernel void vector_sum(__global int *A,__global int *sum) {

    // Get the index of the current element to be processed

    int i = get_global_id(0);

// Do the operation

    sum[0] = A[i] + sum[0];

}

__kernel void vector_sum(__global int *A,int sum) {

    // Get the index of the current element to be processed

    int i = get_global_id(0);

// Do the operation

    sum = A[i] + sum;

}

Does anyone have an idea for the best way to do this?

found solution

I found this resource on the amd site
http://developer.amd.com/documentation/articles/pages/opencl-optimization-case-study-simple-reductions.aspx