#radix #sort #rayon #parallel #multithreaded


A flexible parallel unstable radix sort that supports sorting by any arbitrarily defined sequence of bytes

24 releases (14 breaking)

0.16.0 Sep 19, 2021
0.14.1 Sep 10, 2021
0.5.1 Jul 31, 2021

#180 in Algorithms

Download history 80/week @ 2021-07-24 44/week @ 2021-07-31 43/week @ 2021-08-07 63/week @ 2021-08-14 6/week @ 2021-08-21 1/week @ 2021-08-28 100/week @ 2021-09-04 29/week @ 2021-09-11 67/week @ 2021-09-18

128 downloads per month

Apache-2.0 OR MIT



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rdst is a flexible native Rust implementation of multi-threaded unstable radix sort.


In the simplest case, you can use this sort by simply calling my_vec.radix_sort_unstable(). If you have a custom type to sort, you may need to implement RadixKey for that type.

Default Implementations

RadixKey is implemented for Vec of the following types out-of-the-box:

  • u8, u16, u32, u64, u128, usize
  • i8, i16, i32, i64, i128, isize
  • f32, f64
  • [u8; N]

Implementing RadixKey

To be able to sort custom types, implement RadixKey as below.

  • LEVELS should be set to the total number of bytes you will consider for each item being sorted
  • get_level should return the corresponding bytes from the least significant byte to the most significant byte


  • This allows you to implement radix keys that span multiple values, or to implement radix keys that only look at part of a value.
  • You should try to make this as fast as possible, so consider using branchless implementations wherever possible
impl RadixKey for u16 {
    const LEVELS: usize = 2;

    fn get_level(&self, level: usize) -> u8 {

Partial RadixKey

If you know your type has bytes that will always be zero, you can skip those bytes to speed up the sorting process. For instance, if you have a u32 where values never exceed 10000, you only need to consider two of the bytes. You could implement this as such:

impl RadixKey for u32 {
    const LEVELS: usize = 2;

    fn get_level(&self, level: usize) -> u8 {
        (self >> (level * 8)) as u8

Multi-value RadixKey

If your type has multiple values you need to search by, simply create a RadixKey that spans both values.

impl RadixKey for MyStruct {
    const LEVELS: usize = 4;

    fn get_level(&self, level: usize) -> u8 {
        match level {
          0 => self.key_1[0],
          1 => self.key_1[1],
          2 => self.key_2[0],
          3 => self.key_2[1],


Licensed under either of

at your option.


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.


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