asdf

double start2 = get_time();

    // CPU
    for (int t=0; t<steps; t++) {

        // copy prev
        for (int i = 0; i < N*N; i++) {
            u_prev[i] = u[i];
        }

        for (int i = 0; i < N*N; i++) {
            if ((i< N*N-1-N) && (i%N!=0) && (i%N!=N-1)) {
                u[i] = u_prev[i] + alpha*dt/(h*h) * (u_prev[i+1] + u_prev[i-1] + u_prev[i+N] + u_prev[i-N] - 4*u_prev[i]);
            }
        }
    }

    double stop2 = get_time();

    double elapsed2 = stop2 - start2;
    std::cout<<elapsed2<<"; ";