map with threads

TODO: This is experimental code that needs to be improved

use rayon::prelude::*;
use std::marker::Send;
use std::sync::mpsc;
use std::thread;

fn main() {
    let numbers: Vec<i32> = (1..=10).collect();
    println!("{:?}", numbers);

    let doubles = numbers.iter().map(|num| 2 * num).collect::<Vec<i32>>();
    println!("{:?}", doubles);

    let doubles = numbers.iter().map(double_function).collect::<Vec<i32>>();
    println!("{:?}", doubles);

    let doubles = map_thread(&numbers, double_function, 3);
    println!("{:?}", doubles);

    let doubles = numbers
        .into_par_iter()
        .map(double_function2)
        .collect::<Vec<i32>>();
    //let doubles = numbers.into_par_iter().map(|val| double_function(&val)).collect::<Vec<i32>>();
    println!("{:?}", doubles);
}

fn double_function(num: &i32) -> i32 {
    //println!("{:?}", std::thread::current().id());
    2 * num
}

fn double_function2(num: i32) -> i32 {
    //println!("{:?}", std::thread::current().id());
    2 * num
}

fn map_thread<Tin: Send + Copy + 'static, Tout: Ord + Send + Copy + 'static>(
    params: &[Tin],
    func: fn(&Tin) -> Tout,
    max_threads: i32,
) -> Vec<Tout> {
    //params.iter().map(double_function).collect::<Vec<Tout>>()
    //params.iter().map(func).collect::<Vec<Tout>>()

    let (tx, rx) = mpsc::channel();
    let mut thread_count = 0;
    let mut started = 0;
    let mut finished = 0;
    let mut results: Vec<(i32, Tout)> = vec![];

    for paramx in params.iter() {
        let number = *paramx;
        started += 1;
        let mytx = tx.clone();
        thread::Builder::new()
            .name(format!("{}", started))
            .spawn(move || {
                let id: i32 = thread::current().name().unwrap().parse().unwrap();
                let res = func(&number);
                mytx.send((id, res)).unwrap();
            })
            .unwrap();

        thread_count += 1;
        if thread_count >= max_threads {
            let received = rx.recv().unwrap();
            results.push(received);
            finished += 1;
        }
    }

    for received in rx {
        finished += 1;
        results.push(received);
        if finished >= started {
            break;
        }
    }

    results.sort();
    results.iter().map(|item| item.1).collect::<Vec<Tout>>()
}