【Rust】rustのthread Pool【並列処理】

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use threadpool::ThreadPool;
use std::sync::mpsc;
 
pub struct Data { n: i32 }
 
impl Data {
    fn incr(&mut self) { self.n += 1; }
}
 
fn main() {
     
    let n_workers = 4;
    let pool = ThreadPool::new(n_workers);
    let (tx, rx) = mpsc::channel();
    let v = vec![Data{n:0}, Data{n:1}, Data{n:2}];
    let n_jobs = v.len();
    for mut data in v {
        let tx = tx.clone();
        pool.execute(move || {
            data.incr();
            tx.send(data).expect("channel will be there waiting for the pool");
        });
    }
    let sum: i32 = rx.iter().take(n_jobs).map(|data| data.n).sum();
    println!("sum= {}", sum);
}

sum= 6

thread poolはデフォルトの選択肢？

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use threadpool::ThreadPool;
use std::sync::mpsc;
use std::thread;
 
 
fn main() {
     
    let n_workers = 4;
    let pool = ThreadPool::new(n_workers);
    let (tx, rx) = mpsc::channel();
    for i in 0..20 {
        let tx = tx.clone();
        pool.execute(move || {
            // println!("{}", thread::current().name().unwrap());
            tx.send(i).expect("channel will be there waiting for the pool");       
        });
    }
    for i in 0..20 {
        let j = rx.recv().unwrap();
        println!("{}", j);
    }
}