Code shared from the Rust Playground

playground.rs

use std::time::{ Instant, Duration };

fn benchmark<F: FnOnce()>(f: F) {
    let t0 = Instant::now();
    f();
    let t1 = Instant::now();
    let dt = t1 - t0;
    println!("{}", dt.as_millis());
}

fn main() {
    let a: Vec<_> = (0..10000000).into_iter().collect();
    let mut b = a.clone();
    
    benchmark(move || {
        let c: Vec<_> = a.into_iter().filter(|&x| x % 2 == 0).collect();
        println!("{}", c.len());
    });
    
    benchmark(|| {
        b.retain(|&x| x % 2 == 0);
        println!("{}", b.len());
    });
}