Simple embarassingly parallel Rayon example

rayon_test.rs

/* sample output (on an 8 core machine):

time elapsed (parallel): 732.39394ms
999: false
time elapsed (serial): 5.857433675s
999: false

5.857433675 seconds / 732.39394 ms = 7.99765448 ~= 8
*/

use rayon::prelude::*;
use std::thread::sleep;
use std::time::{Duration, Instant};

fn main() {
    const SZ: usize = 1000;
    let mut v = vec![0usize; SZ];
    let mut result = vec![false; SZ];
    let mut start = Instant::now();
    
    v.par_iter_mut().enumerate().zip_eq(result.par_iter_mut()).for_each(|((i, x), r)| { 
        sleep(Duration::from_millis(5));
        *x = i;
        *r = *x % 2 == 0;
    });
    let mut elapsed = start.elapsed();
    
    println!("time elapsed (parallel): {:?}", elapsed);
    println!("{}: {}", v.last().unwrap(), result.last().unwrap());

    v = vec![0usize; SZ];
    result = vec![false; SZ];
    start = Instant::now();
    v.iter_mut().enumerate().zip(result.iter_mut()).for_each(|((i, x), r)| { 
        sleep(Duration::from_millis(5));
        *x = i;
        *r = *x % 2 == 0;
    });
    elapsed = start.elapsed();

    println!("time elapsed (serial): {:?}", elapsed);
    println!("{}: {}", v.last().unwrap(), result.last().unwrap());
}