qvnt 0.4.4

Advanced quantum computation simulator.
Documentation 
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use std::sync::RwLock;

use lazy_static::*;
use rayon::*;

lazy_static! {
    static ref GLOBAL_POOL: RwLock<Option<(usize, ThreadPool)>> = RwLock::new(None);
}

fn get_current_num_threads() -> Option<usize> {
    GLOBAL_POOL
        .read()
        .unwrap()
        .as_ref()
        .map(|(th, _)| th)
        .cloned()
}

fn global_install_unchecked<OP, R>(op: OP) -> R
where
    OP: FnOnce() -> R + Send,
    R: Send,
{
    GLOBAL_POOL
        .read()
        .unwrap()
        .as_ref()
        .map(|(_, tp)| tp.install(op))
        .unwrap()
}

fn set_num_threads(num_threads: usize) {
    *GLOBAL_POOL.write().unwrap() = Some((
        num_threads,
        ThreadPoolBuilder::new()
            .num_threads(num_threads)
            .build()
            .unwrap(),
    ));
}

pub fn global_install<OP, R>(num_threads: usize, op: OP) -> R
where
    OP: FnOnce() -> R + Send,
    R: Send,
{
    match get_current_num_threads() {
        Some(th) if th == num_threads => {}
        _ => set_num_threads(num_threads),
    };
    global_install_unchecked(op)
}