Codingame thread performance test, tl;dr unthreaded runs ~2.5x faster

main.rs

use std::sync::{Mutex, Arc};
use std::thread;
use std::time::Instant;

fn main() {
    let threaded_counter = Arc::new(Mutex::new(0));
    let mut handles = vec![];

    let timer = Instant::now();
    for _ in 0..2 {
        let counter = Arc::clone(&threaded_counter);
        let handle = thread::spawn(move || {
            let result = compute();
            let mut num = counter.lock().unwrap();

            *num += result;
        });
        handles.push(handle);
    }

    for handle in handles {
        handle.join().unwrap();
    }
    let duration = timer.elapsed();

    eprintln!("  Threaded version, Result: {}, Duration: {} ns", *threaded_counter.lock().unwrap(), duration.as_nanos());
    
    let timer = Instant::now();
    let mut unthreaded_counter = 0;
    for _ in 0..2 {
            let result = compute();
            unthreaded_counter += result;
    }
    let duration = timer.elapsed();

    eprintln!("Unthreaded version, Result: {}, Duration: {} ns", unthreaded_counter, duration.as_nanos());

}

fn compute() -> i32 {
    let mut result: i32 = 0;
    for i in 0..1000 {
        result += i;
    }
    
    result
}