rayon 0.7.1

Simple work-stealing parallelism for Rust
Documentation 
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use std::sync::atomic::AtomicUsize;
use super::*;

#[test]
fn same_range_first_consumers_return_correct_answer() {
    let find_op = |x: &i32| x % 2 == 0;
    let first_found = AtomicUsize::new(usize::max_value());
    let far_right_consumer = FindConsumer::new(&find_op, MatchPosition::Leftmost, &first_found);

    // We save a consumer that will be far to the right of the main consumer (and therefore not
    // sharing an index range with that consumer) for fullness testing
    let consumer = far_right_consumer.split_off_left();

    // split until we have an indivisible range
    let bits_in_usize = usize::min_value().count_zeros();

    for _ in 0..bits_in_usize {
        consumer.split_off_left();
    }

    let reducer = consumer.to_reducer();
    // the left and right folders should now have the same range, having
    // exhausted the resolution of usize
    let left_folder = consumer.split_off_left().into_folder();
    let right_folder = consumer.into_folder();

    let left_folder = left_folder.consume(0).consume(1);
    assert_eq!(left_folder.boundary, right_folder.boundary);
    // expect not full even though a better match has been found because the
    // ranges are the same
    assert!(!right_folder.full());
    assert!(far_right_consumer.full());
    let right_folder = right_folder.consume(2).consume(3);
    assert_eq!(reducer.reduce(left_folder.complete(), right_folder.complete()),
               Some(0));
}

#[test]
fn same_range_last_consumers_return_correct_answer() {
    let find_op = |x: &i32| x % 2 == 0;
    let last_found = AtomicUsize::new(0);
    let consumer = FindConsumer::new(&find_op, MatchPosition::Rightmost, &last_found);

    // We save a consumer that will be far to the left of the main consumer (and therefore not
    // sharing an index range with that consumer) for fullness testing
    let far_left_consumer = consumer.split_off_left();

    // split until we have an indivisible range
    let bits_in_usize = usize::min_value().count_zeros();
    for _ in 0..bits_in_usize {
        consumer.split_off_left();
    }

    let reducer = consumer.to_reducer();
    // due to the exact calculation in split_off_left, the very last consumer has a
    // range of width 2, so we use the second-to-last consumer instead to get
    // the same boundary on both folders
    let consumer = consumer.split_off_left();
    let left_folder = consumer.split_off_left().into_folder();
    let right_folder = consumer.into_folder();
    let right_folder = right_folder.consume(2).consume(3);
    assert_eq!(left_folder.boundary, right_folder.boundary);
    // expect not full even though a better match has been found because the
    // ranges are the same
    assert!(!left_folder.full());
    assert!(far_left_consumer.full());
    let left_folder = left_folder.consume(0).consume(1);
    assert_eq!(reducer.reduce(left_folder.complete(), right_folder.complete()),
               Some(2));
}