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#![feature(scoped)]
#![cfg_attr(test, feature(test))]
use std::sync::{Arc};
use std::thread;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::mem;
pub fn pmap<A, B, F>(array: &[A], out:&mut [B], max: usize, f: F)
where F: Send+Sync, F: Fn(A)->B, A: Send+Sync+Copy, B: Send+Sync
{
assert!(out.len() >= array.len());
let idx = &AtomicUsize::new(0);
let len = array.len();
let array = Arc::new(array);
let f = Arc::new(f);
{
let mut threads: Vec<thread::JoinGuard<bool>> = Vec::new();
for _ in 0..max {
let data: &mut [B] = unsafe{ mem::transmute_copy(&out) };
let f = f.clone();
let array = array.clone();
let trd = thread::scoped(move|| {
loop {
let i = idx.fetch_add(1, Ordering::Relaxed);
if i >= len {
return true;
}
let in_data = array[i];
let out_data = f(in_data);
data[i] = out_data;
}
});
threads.push(trd);
}
}
}
#[cfg(test)]
mod tests {
extern crate test;
use super::pmap;
#[test]
fn it_works() {
let behind = [1usize, 2, 3, 4, 5];
let mut thing = [0usize; 5];
pmap(&behind, &mut thing, 2, inc);
let out = [1usize, 2, 6,24,120];
assert_eq!(thing, out);
}
fn inc (x: usize) -> usize {
inc2(1, x)
}
fn inc2 (acc: usize, x: usize) -> usize {
match x {
1=> acc,
_=> inc2(acc * x, x - 1)
}
}
}
#[cfg(test)]
mod bench {
extern crate test;
extern crate rand;
use super::pmap;
use self::test::Bencher;
use self::rand::Rng;
fn fill(array: &mut [u8]) {
let mut rng = rand::chacha::ChaChaRng::new_unseeded();
let len = array.len();
for i in 0..len {
array[i] = rng.gen::<u8>();
}
}
#[bench]
fn one(bh: & mut Bencher) {
let mut behind = [0u8; 8000];
let mut thing = [0u8;8000];
fill(&mut behind);
bh.iter( || {
pmap(&behind, &mut thing, 1, inc);
});
bh.bytes = behind.len() as u64;
}
#[bench]
fn two(bh: & mut Bencher) {
let mut behind = [0u8; 8000];
let mut thing = [0u8;8000];
fill(&mut behind);
bh.iter( || {
pmap(&behind, &mut thing, 2, inc);
});
bh.bytes = behind.len() as u64;
}
#[bench]
fn three(bh: & mut Bencher) {
let mut behind = [0u8; 8000];
let mut thing = [0u8; 8000];
fill(&mut behind);
bh.iter( || {
pmap(&behind, &mut thing, 3, inc);
});
bh.bytes = behind.len() as u64;
}
#[bench]
fn four(bh: & mut Bencher) {
let mut behind = [0u8; 8000];
let mut thing = [0u8;8000];
fill(&mut behind);
bh.iter( || {
pmap(&behind, &mut thing, 4, inc);
});
bh.bytes = behind.len() as u64;
}
#[bench]
fn six(bh: & mut Bencher) {
let mut behind = [0u8; 8000];
let mut thing = [0u8;8000];
fill(&mut behind);
bh.iter( || {
pmap(&behind, &mut thing, 6, inc);
});
bh.bytes = behind.len() as u64;
}
#[bench]
fn eight(bh: & mut Bencher) {
let mut behind = [0u8; 8000];
let mut thing = [0u8;8000];
fill(&mut behind);
bh.iter( || {
pmap(&behind, &mut thing, 8, inc);
});
bh.bytes = behind.len() as u64;
}
fn inc (x: u8) -> u8 {
inc2(1, x)
}
fn inc2 (acc: u8, x: u8) -> u8 {
match x {
1=> acc,
_=> inc2(acc * x, x - 1)
}
}
}