threadteam 0.1.3

Scoped CPU thread-team placement token: a Pool and a non-Clone Exec with fork, for_ranges, external and broadcast; no Rayon type in the public API.
Documentation 
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//! The process-global Rayon pool must never be started implicitly.
//!
//! This file holds a single test so that the process is pristine: after serial
//! and pooled work, installing a global pool must still succeed, which fails
//! once anything has started the global registry.
#![cfg(all(feature = "parallel", feature = "ledger"))]

use std::num::NonZeroUsize;
use threadteam::{Exec, Pool};

#[test]
fn global_pool_is_never_started() {
    let nz = NonZeroUsize::MIN;
    Exec::serial().fork(4, |_, child| child.for_ranges(8, nz, |_| {}));
    Exec::serial().for_ranges(16, nz, |_| {});
    Exec::serial().broadcast(|_| {}).unwrap();

    let pool = Pool::builder().threads(3).build().unwrap();
    assert!(pool.width().get() >= 1);
    let mut exec = Exec::new(&pool, 3).unwrap();
    exec.reborrow()
        .fork(5, |_, child| child.for_ranges(32, nz, |_| {}));
    exec.reborrow().for_ranges(100, nz, |_| {});
    exec.reborrow().broadcast(|_| {}).unwrap();
    exec.reborrow().external(|width| width.get());
    Exec::new(&pool, 1).unwrap().fork(3, |_, _| {});

    // A worker of the pool calling back into its own pool.
    Exec::new(&pool, 2).unwrap().fork(2, |_, _| {
        Exec::new(&pool, 2).unwrap().for_ranges(8, nz, |_| {});
    });

    assert!(
        threadteam::ledger::global_pool_unstarted(),
        "the global pool was started by threadteam"
    );
}