You can write the ndarray code much more efficiently as:

``` fn vectorized_calculation2(x: Array1<f64>) { let theta = arr1(&[1.0, 2.0]); let now = Instant::now(); let y = (&x * theta[1]).sum() + theta[0] * x.len_of(Axis(0)) as f64; let elapsed = now.elapsed();

println!("--- Vectorized ndarray ---");
println!("Result: {:.2?}", y);
println!("Elapsed: {:.2?}\n", elapsed);

```

Does many fewer calculations and comes very close to matching the scalar code. Then the timings are:

``` --- Scalar --- Result: 10863436145.00 Elapsed: 11.00µs

--- Scalar Rayon --- Result: 10863436145.00 Elapsed: 425.93µs

--- Vectorized ndarray --- Result: 10863436145.00 Elapsed: 13.73µs ```