par_bridge_recursion.rs

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use rayon::prelude::*;

use std::iter::once_with;

const N: usize = 100_000;

#[test]

fn par_bridge_recursion() {

    let pool = rayon::ThreadPoolBuilder::new()

        .num_threads(10)

        .build()

        .unwrap();

    let seq: Vec<_> = (0..N).map(|i| (i, i.to_string())).collect();

    pool.broadcast(|_| {

        let mut par: Vec<_> = (0..N)

            .into_par_iter()

            .flat_map(|i| {

                once_with(move || {

                    // Using rayon within the serial iterator creates an opportunity for

                    // work-stealing to make par_bridge's mutex accidentally recursive.

                    rayon::join(move || i, move || i.to_string())

})

                .par_bridge()

})

            .collect();

        par.par_sort_unstable();

        assert_eq!(seq, par);

});