prosense_test.rs

use std::sync::Arc;
use std::thread;

const THRESHOLD: usize = 1000;

fn main() {
    let input: Vec<u64> = (0..2000).collect();
    let result = splitter(input.clone(), |v| v * 2);
    assert_eq!(
        result,
        input.into_iter().map(|v| v * 2).collect::<Vec<u64>>()
    );
}

fn splitter<T, R, F>(values: Vec<T>, handler: F) -> Vec<R>
where
    T: Clone + Send + 'static,
    R: Send + 'static,
    F: (Fn(T) -> R) + Send + Sync + 'static,
{
    if values.len() < THRESHOLD {
        return values.into_iter().map(handler).collect();
    }

    let input = values[THRESHOLD..].to_owned();
    let handler = Arc::new(handler);
    let join_handle = {
        let handler = Arc::clone(&handler);
        thread::spawn(move || input.into_iter().map(|v| handler(v)).collect::<Vec<R>>())
    };

    let mut result: Vec<R> = values[..THRESHOLD]
        .into_iter()
        .cloned()
        .map(|v| handler(v))
        .collect();

    result.append(&mut join_handle.join().unwrap());
    result
}