#include <iostream>
#include <math.h>

__global__
void add (int n, float* x, float* y){
    for(int i = 0; i< n; i++)
        y[i] = x[i] +y[i];
}


int main (void) {
    int N = 1<<20;
    float *x, *y;
    cudaMallocManaged(&x, N*sizeof(float));
    cudaMallocManaged(&y, N*sizeof(float));


    for (int i = 0; i<N; i++){
        x[i] = 1.0f;
        y[i] = 2.0f;
    }

    add<<<1,1>>>(N, x, y );
    cudaDeviceSynchronize();

    float maxError= 0.0f;
    for (int i =0; i < N; i++){
        maxError = fmax(maxError, fabs(y[i] -3.0f));
    }
    std::cout << "Max error: " << maxError << std::endl;

    cudaFree(x);
    cudaFree(y);
    return 0;
}