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use std::slice;
use ::Unsigned;
use stash::Stash;
use batched_vec::BatchedVecX256;
macro_rules! per_cache_line {
($t:ty) => {{ ::std::cmp::max(64 / ::std::mem::size_of::<$t>(), 4) }}
}
macro_rules! lines_per_page {
() => {{ 2 * 4096 / 64 }}
}
pub struct RadixSorter<T> {
shuffler: RadixShuffler<T>,
}
impl<T> RadixSorter<T> {
pub fn new() -> RadixSorter<T> {
RadixSorter {
shuffler: RadixShuffler::new(),
}
}
#[inline]
pub fn extend<U: Unsigned, F: Fn(&T)->U, I: Iterator<Item=T>>(&mut self, iterator: I, function: &F) {
for element in iterator {
self.push(element, function);
}
}
#[inline]
pub fn push<U: Unsigned, F: Fn(&T)->U>(&mut self, element: T, function: &F) {
self.shuffler.push(element, &|x| (function(x).as_u64() % 256) as u8);
}
#[inline]
pub fn push_batch<U: Unsigned, F: Fn(&T)->U>(&mut self, batch: Vec<T>, function: &F) {
self.shuffler.push_batch(batch, &|x| (function(x).as_u64() % 256) as u8);
}
pub fn sort<U: Unsigned, F: Fn(&T)->U>(&mut self, batches: &mut Vec<Vec<T>>, function: &F) {
for batch in batches.drain(..) {
self.push_batch(batch, function);
}
self.finish_into(batches, function);
}
pub fn finish<U: Unsigned, F: Fn(&T)->U>(&mut self, function: &F) -> Vec<Vec<T>> {
let mut result = Vec::new();
self.finish_into(&mut result, function);
result
}
pub fn finish_into<U: Unsigned, F: Fn(&T)->U>(&mut self, target: &mut Vec<Vec<T>>, function: &F) {
self.shuffler.finish_into(target);
for byte in 1..(<U as Unsigned>::bytes()) {
self.reshuffle(target, &|x| ((function(x).as_u64() >> (8 * byte)) % 256) as u8);
}
}
pub fn recycle(&mut self, buffers: &mut Vec<Vec<T>>) {
self.rebalance(buffers, usize::max_value());
}
pub fn rebalance(&mut self, buffers: &mut Vec<Vec<T>>, intended: usize) {
self.shuffler.stash.rebalance(buffers, intended);
}
#[inline(always)]
fn reshuffle<F: Fn(&T)->u8>(&mut self, buffers: &mut Vec<Vec<T>>, function: &F) {
for buffer in buffers.drain(..) {
self.shuffler.push_batch(buffer, function);
}
self.shuffler.finish_into(buffers);
}
}
pub struct RadixShuffler<T> {
staged: Vec<T>,
counts: [u8; 256],
buckets: BatchedVecX256<T>,
stash: Stash<T>,
}
impl<T> RadixShuffler<T> {
fn new() -> RadixShuffler<T> {
let staged = Vec::with_capacity(256 * per_cache_line!(T));
let addr: usize = unsafe { ::std::mem::transmute(staged.as_ptr()) };
assert_eq!(addr % 64, 0);
RadixShuffler {
staged: staged,
counts: [0; 256],
buckets: BatchedVecX256::new(),
stash: Stash::new(lines_per_page!() * per_cache_line!(T)),
}
}
fn push_batch<F: Fn(&T)->u8>(&mut self, mut elements: Vec<T>, function: &F) {
for element in elements.drain(..) {
self.push(element, function);
}
self.stash.give(elements);
}
#[inline]
fn push<F: Fn(&T)->u8>(&mut self, element: T, function: &F) {
let byte = function(&element);
unsafe {
if *self.counts.get_unchecked(byte as usize) as usize == per_cache_line!(T) {
let staged_elements = slice::from_raw_parts(
self.staged.as_ptr().offset(per_cache_line!(T) as isize * byte as isize),
per_cache_line!(T)
);
self.buckets.get_mut(byte).push_all(staged_elements, &mut self.stash);
self.counts[byte as usize] = 0;
}
let offset = per_cache_line!(T) as isize * byte as isize + *self.counts.get_unchecked(byte as usize) as isize;
::std::ptr::write(self.staged.as_mut_ptr().offset(offset), element);
*self.counts.get_unchecked_mut(byte as usize) += 1;
}
}
fn finish_into(&mut self, target: &mut Vec<Vec<T>>) {
for byte in 0..256 {
self.buckets.get_mut(byte as u8).finish_into(target);
if target.last().map(|x| x.capacity() - x.len() >= self.counts[byte] as usize) != Some(true) {
target.push(self.stash.get());
}
let last = target.last_mut().unwrap();
for i in 0..self.counts[byte] {
unsafe {
last.push(::std::ptr::read(self.staged.as_mut_ptr().offset(per_cache_line!(T) as isize * byte as isize + i as isize)));
}
}
self.counts[byte] = 0;
}
}
}
mod test {
#[test]
fn test1() {
let size = 10;
let mut vector = Vec::<usize>::with_capacity(size);
for index in 0..size {
vector.push(index);
}
for index in 0..size {
vector.push(size - index);
}
let mut sorter = super::RadixSorter::new();
for &element in &vector {
sorter.push(element, &|&x| x);
}
vector.sort();
let mut result = Vec::new();
for element in sorter.finish(&|&x| x).into_iter().flat_map(|x| x.into_iter()) {
result.push(element);
}
assert_eq!(result, vector);
}
#[test]
fn test_large() {
let size = 1_000_000;
let mut vector = Vec::<[usize; 16]>::with_capacity(size);
for index in 0..size {
vector.push([index; 16]);
}
for index in 0..size {
vector.push([size - index; 16]);
}
let mut sorter = super::RadixSorter::new();
for &element in &vector {
sorter.push(element, &|&x| x[0]);
}
vector.sort_by(|x, y| x[0].cmp(&y[0]));
let mut result = Vec::new();
for element in sorter.finish(&|&x| x[0]).into_iter().flat_map(|x| x.into_iter()) {
result.push(element);
}
assert_eq!(result, vector);
}
}