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|
use std::mem;
pub trait RadixFilters: 'static {
const FILTERS: &'static [fn(&Self) -> u8];
}
impl RadixFilters for u32 {
const FILTERS: &'static [fn(&Self) -> u8] = &[
|x| ((x & 0x000000ff) >> (8 * 0)) as _,
|x| ((x & 0x0000ff00) >> (8 * 1)) as _,
|x| ((x & 0x00ff0000) >> (8 * 2)) as _,
|x| ((x & 0xff000000) >> (8 * 3)) as _,
];
}
impl RadixFilters for i32 {
const FILTERS: &'static [fn(&Self) -> u8] = &[
|x| ((x & 0x000000ff) >> (8 * 0)) as _,
|x| ((x & 0x0000ff00) >> (8 * 1)) as _,
|x| ((x & 0x00ff0000) >> (8 * 2)) as _,
|x| (((x & 0xff000000u32 as i32) ^ (1 << 31)) >> (8 * 3)) as _,
];
}
impl RadixFilters for u64 {
const FILTERS: &'static [fn(&Self) -> u8] = &[
|x| ((x & 0x00000000000000ff) >> (8 * 0)) as _,
|x| ((x & 0x000000000000ff00) >> (8 * 1)) as _,
|x| ((x & 0x0000000000ff0000) >> (8 * 2)) as _,
|x| ((x & 0x00000000ff000000) >> (8 * 3)) as _,
|x| ((x & 0x000000ff00000000) >> (8 * 4)) as _,
|x| ((x & 0x0000ff0000000000) >> (8 * 5)) as _,
|x| ((x & 0x00ff000000000000) >> (8 * 6)) as _,
|x| ((x & 0xff00000000000000) >> (8 * 7)) as _,
];
}
pub fn radix_sort_with<T>(xs: &mut [T], temp: &mut [T])
where
T: Default + Copy + Clone + RadixFilters,
{
// The first thing that happens it that these two are swapped so thats why this seems backwards
let mut output = xs;
let mut input = temp;
debug_assert!(T::FILTERS.len() % 2 == 0);
for f in T::FILTERS {
mem::swap(&mut input, &mut output);
let mut counts = [0; 256];
for x in input.iter() {
counts[f(x) as usize] += 1;
}
let mut sum = 0;
for c in &mut counts {
sum += *c;
*c = sum;
}
for x in input.iter_mut().rev() {
let fx = f(x) as usize;
counts[fx] -= 1;
output[counts[fx]] = *x;
}
}
}
pub fn radix_sort<T>(xs: &mut [T])
where
T: Default + Copy + Clone + RadixFilters,
{
let n = xs.len();
radix_sort_with(xs, vec![Default::default(); n].as_mut_slice());
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn basic_rand() {
let mut r = rand_pcg::Pcg32::new(0xcafef00dd15ea5e5, 0xa02bdbf7bb3c0a7);
let mut xs: Vec<u32> = (0..1_000_000).map(|_| r.next_u32()).collect();
radix_sort(&mut xs);
for w in xs.as_slice().windows(2) {
assert!(w[0] <= w[1]);
}
}
#[test]
fn negatives() {
let mut r = rand_pcg::Pcg32::new(0xcafef00dd15ea5e5, 0xa02bdbf7bb3c0a7);
let mut xs: Vec<i32> = (0..1_000_000).map(|_| r.next_u32() as i32).collect();
radix_sort(&mut xs);
for w in xs.as_slice().windows(2) {
assert!(w[0] <= w[1], "{} <= {}", w[0], w[1]);
}
}
extern crate test;
use rand::RngCore;
use test::{black_box, Bencher};
#[bench]
fn std_u32_x1e6(b: &mut Bencher) {
let mut r = rand_pcg::Pcg32::new(0xcafef00dd15ea5e5, 0xa02bdbf7bb3c0a7);
let xs: Vec<u32> = (0..1_000_000).map(|_| r.next_u32()).collect();
b.iter(|| {
let mut xs = black_box(xs.clone());
xs.sort();
black_box(xs);
});
}
#[bench]
fn radix_u32_x1e6(b: &mut Bencher) {
let mut r = rand_pcg::Pcg32::new(0xcafef00dd15ea5e5, 0xa02bdbf7bb3c0a7);
let xs: Vec<u32> = (0..1_000_000).map(|_| r.next_u32()).collect();
b.iter(|| {
let mut xs = black_box(xs.clone());
radix_sort(&mut xs);
black_box(xs);
});
}
#[bench]
fn std_u64_x1e6(b: &mut Bencher) {
let mut r = rand_pcg::Pcg32::new(0xcafef00dd15ea5e5, 0xa02bdbf7bb3c0a7);
let xs: Vec<u64> = (0..1_000_000).map(|_| r.next_u64()).collect();
b.iter(|| {
let mut xs = black_box(xs.clone());
xs.sort();
black_box(xs);
});
}
#[bench]
fn radix_u64_x1e6(b: &mut Bencher) {
let mut r = rand_pcg::Pcg32::new(0xcafef00dd15ea5e5, 0xa02bdbf7bb3c0a7);
let xs: Vec<u64> = (0..1_000_000).map(|_| r.next_u64()).collect();
b.iter(|| {
let mut xs = black_box(xs.clone());
radix_sort(&mut xs);
black_box(xs);
});
}
}
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