I am trying to test the std::simd to measure performance , but I am new to this stuff, so I am wondering if I am doing things wrong?

simd_test.rs

#![feature(portable_simd)]
use std::simd::Simd;
use std::array;
use std::time::Duration;
use instant;
use rand::prelude::*;

const lanes : usize = 16;

fn main() {

    println!("Hello, world!");
    let (duration,simd_add,simd_prod) = do_simd_calculation(1_000_000);
    println!("We spent {} seconds doing a million simds and simd_add = {}, and simd_prod = {}",duration.as_secs_f32(),simd_add,simd_prod);

    let (duration,simd_add,simd_prod) = do_non_simd_calculation(1_000_000);
    println!("We spent {} seconds doing a million non simds",duration.as_secs_f32());
}

fn do_non_simd_calculation(rep_count:usize)->(Duration,f32,f32){
    let start = instant::Instant::now();
    let mut total_sum = 0.0;
    let mut total_prod = 0.0;
    let mut rng = thread_rng();

    for _ in 0..rep_count{

        let (a_vec,b_vec)  = create_random_float_arrays(lanes,&mut rng);
        let a: [f32; lanes] = a_vec.try_into().unwrap();
        let b: [f32; lanes] = b_vec.try_into().unwrap();

        let sum:[f32;lanes] = array::from_fn(|i| a[i] + b[i]);
        let prod:[f32;lanes] = array::from_fn(|i| a[i] * b[i]);

        for val in sum{
            total_sum+=val;
        }
        for val in prod{
            total_prod+=val;
        }

    }
    let now = instant::Instant::now();
    (now-start,total_sum,total_prod)
}

fn do_simd_calculation(rep_count:usize)->(Duration,f32,f32){
    let start = instant::Instant::now();
    let mut total_sum = 0.0;
    let mut total_prod = 0.0;
    let mut rng = thread_rng();
    for _ in 0..rep_count{

        let (a_vec,b_vec)  = create_random_float_arrays(lanes,&mut rng);
        let a: [f32; lanes] = a_vec.try_into().unwrap();
        let b: [f32; lanes] = b_vec.try_into().unwrap();
        // `Simd<T, N>` implements `From<[T; N]>`
        let (v, w) = (Simd::from(a), Simd::from(b));
        let sum = v + w;
        let product = v * w;
        for val in sum.as_array(){
            total_sum+=val;
        }
        for val in product.as_array(){
            total_prod+=val;
        }

    }
    let now = instant::Instant::now();
    (now-start,total_sum,total_prod)
}

fn create_random_float_arrays(num_floats: usize,randomizer: &mut ThreadRng)-> (Vec<f32>,Vec<f32>)
{
    let mut a_vec: Vec<f32> = Vec::new();
    let mut b_vec: Vec<f32> = Vec::new();

    for i in 0.. num_floats {
        a_vec.push(randomizer.gen());
        b_vec.push(randomizer.gen());
    }
    (a_vec,b_vec)
}