Expand description
§rdst
rdst is a flexible native Rust implementation of multi-threaded unstable radix sort.
§Usage
use rdst::RadixSort;
let mut my_vec = vec![4, 7, 1, 6, 5, 3, 2, 8, 9];
my_vec.radix_sort_unstable();
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
and [T]
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 sortedget_level
should return the corresponding bytes from the least significant byte to the most significant byte
Notes:
- 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
use rdst::RadixKey;
struct MyType(u32);
impl RadixKey for MyType {
const LEVELS: usize = 4;
#[inline]
fn get_level(&self, level: usize) -> u8 {
(self.0 >> (level * 8)) as 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:
use rdst::RadixKey;
struct U32Wrapper(u32);
impl RadixKey for U32Wrapper {
const LEVELS: usize = 2;
#[inline]
fn get_level(&self, level: usize) -> u8 {
(self.0 >> (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.
use rdst::RadixKey;
struct MyStruct {
key_1: u8,
key_2: u8,
key_3: u8,
}
impl RadixKey for MyStruct {
const LEVELS: usize = 3;
#[inline]
fn get_level(&self, level: usize) -> u8 {
match level {
0 => self.key_1,
1 => self.key_2,
_ => self.key_3,
}
}
}
§Low-memory Variant
use rdst::RadixSort;
let mut my_vec: Vec<usize> = vec![10, 15, 0, 22, 9];
my_vec
.radix_sort_builder()
.with_low_mem_tuner()
.sort();
This library also includes a mostly in-place variant of radix sort. This is useful in cases where memory or memory bandwidth are more limited. Generally, this algorithm is slightly slower than the standard algorithm, however in specific circumstances this algorithm may even provide a speed boost. It is worth benchmarking against your use-case if you need the ultimate level of performance.
§Single-threaded Variant
To make this library use an entirely single-threaded set of algorithms and processes, you can use the following snippet.
use rdst::RadixSort;
let mut my_vec: Vec<usize> = vec![10, 15, 0, 22, 9];
my_vec
.radix_sort_builder()
// Use a tuner that only includes single-threaded algorithms
.with_single_threaded_tuner()
// Don't run multiple algorithms (even single-threaded ones) in parallel
.with_parallel(false)
.sort();
NOTE: If you are ONLY using the single-threaded variant of this radix sort, you can disable the default "multi-threaded"
feature on the rdst
dependency to remove large sub-dependencies like Rayon.
[dependencies.rdst]
version = "x.y.z"
default-features = false
With the "multi-threaded"
feature disabled, even the default my_data.radix_sort_unstable()
will use a single-threaded tuner.
§Custom Tuners
Tuners are things which you can implement to control which sorting algorithms are used. There are many radix sorting algorithms implemented as part of this crate, and they all have their pros and cons. If you have a very specific use-case it may be worth your time to tune the sort yourself.
use rdst::RadixSort;
use rdst::tuner::{Algorithm, Tuner, TuningParams};
struct MyTuner;
impl Tuner for MyTuner {
fn pick_algorithm(&self, p: &TuningParams, _counts: &[usize]) -> Algorithm {
if p.input_len >= 500_000 {
Algorithm::Ska
} else {
Algorithm::Lsb
}
}
}
let mut my_vec: Vec<usize> = vec![10, 25, 9, 22, 6];
my_vec
.radix_sort_builder()
.with_tuner(&MyTuner {})
.sort();
§License
Licensed under either of
- Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.
§Contribution
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.