How to Implement Fan-Out/Fan-In Concurrency in Rust

Implement fan-out/fan-in in Rust by spawning worker threads for each task (fan-out) and collecting their results via channels (fan-in).

use std::thread;
use std::sync::mpsc;

fn main() {
    let (tx, rx) = mpsc::channel();
    let mut handles = vec![];

    // Fan-out: spawn workers
    for i in 0..4 {
        let tx = tx.clone();
        handles.push(thread::spawn(move || {
            tx.send(i * 2).unwrap();
        }));
    }
    drop(tx);

    // Fan-in: collect results
    let results: Vec<i32> = rx.iter().collect();
    for h in handles { h.join().unwrap(); }
    println!("{:?}", results);
}

Fan-out means splitting one big job into many smaller jobs running at the same time. Fan-in means gathering all the results from those jobs back into one place. Think of it like a manager assigning tasks to a team and then waiting for everyone to finish before compiling the final report.