Go will support a new sorting algorithm in the next version: pdqsort

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Following the support of generics in Go 1.18 , Go will support the pdqsort sorting algorithm in the next version, which has once again caused a heated discussion among developers.

At present, the relevant functional description of pdqsort is introduced in the latest commit of the Go repository:

In all benchmarks, pdqsort did not appear to be slower than other previous algorithms;
In common patterns, pdqsort is generally faster (i.e. 10x faster in sorting slices)

What is the pdqsort sorting algorithm?

pdqsort, short for Pattern-defeating quicksort, is a novel sorting algorithm that combines the fast average case of random quicksort with the worst case fast of heap sort, while achieving linear time on inputs with specific patterns. pdqsort is an extension and improvement of David Mussers' introsort. All code is free under the zlib license.

It is currently implemented in C++ and Rust, and according to the actual measurement of many developers, pdqsort, which is more commonly used introsort, will have a greater performance improvement.

C++ implementation: https://github.com/orlp/pdqsort
Rust implementation: https://docs.rs/pdqsort/latest/pdqsort/

C++ code Demo:

#include <algorithm>
#include <functional>
#include <array>
#include <iostream>
#include <string_view>
 
int main()
{
    std::array<int, 10> s = {5, 7, 4, 2, 8, 6, 1, 9, 0, 3};
 
    auto print = [&s](std::string_view const rem) {
        for (auto a : s) {
            std::cout << a << ' ';
        }
        std::cout << ": " << rem << '\n';
    };
 
    std::sort(s.begin(), s.end());
    print("sorted with the default operator<");
 
    std::sort(s.begin(), s.end(), std::greater<int>());
    print("sorted with the standard library compare function object");
 
    struct {
        bool operator()(int a, int b) const { return a < b; }
    } customLess;
    std::sort(s.begin(), s.end(), customLess);
    print("sorted with a custom function object");
 
    std::sort(s.begin(), s.end(), [](int a, int b) {
        return a > b;
    });
    print("sorted with a lambda expression");
}

Results of the:

0 1 2 3 4 5 6 7 8 9 : sorted with the default operator< 9 8 7 6 5 4 3 2 1 0 : sorted with the standard library compare function object 0 1 2 3 4 5 6 7 8 9 : sorted with a custom function object 9 8 7 6 5 4 3 2 1 0 : sorted with a lambda expression

Rust code Demo:

extern crate pdqsort;


let mut v = [-5i32, 4, 1, -3, 2];


pdqsort::sort(&mut v);
assert!(v == [-5, -3, 1, 2, 4]);


pdqsort::sort_by(&mut v, |a, b| b.cmp(a));
assert!(v == [4, 2, 1, -3, -5]);


pdqsort::sort_by_key(&mut v, |k| k.abs());
assert!(v == [1, 2, -3, 4, -5]);

As for Go's support for the pdqsort algorithm, there has been a lot of discussion on HN. Some people said: We have been studying sorting algorithms for so long, and we are surprised that we can still come up with optimization schemes that can produce actual improvements. What do you think about this, let's get started and experience it.

Reference link:

https://github.com/golang/go/commit/72e77a7f41bbf45d466119444307fd3ae996e257
https://news.ycombinator.com/item?id=31106157
https://en.cppreference.com/w/cpp/algorithm/sort

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Go will support a new sorting algorithm in the next version: pdqsort

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