Posts Tagged ‘programming’

[rust] fast hashmap

December 4, 2019 Leave a comment

In Rust, the stdlib’s HashMap is quite slow. It’s secure, resistant against DOS attacks, but slow. If I write a tool that I want to use myself, it doesn’t have to be cryptographically secure. I want it to be fast.

I tried several alternatives and fxhash proved to be the fastest. I compared the stdlib, hashbrown, ahash and fxhash, and fxhash proved to be the fastest.

In Cargo.toml:

fxhash = "0.2"

In your code:

use fxhash::FxHashMap as HashMap;    // after these renames, it can be used
use fxhash::FxHashSet as HashSet;    // as a drop-in replacement

fn main() {
    let mut map: HashMap = HashMap::default();    // !!! it's called ::default(), not ::new()
    map.insert(1, "one");
    map.insert(2, "two");

    println!("{:?}", map);                  // {2: "two", 1: "one"}
    println!("{}", map.get(&1).unwrap());   // one

I asked on GitHub how to have a fast hashmap in Rust, and the author of hashbrown directed me to these crates. As Amanieu explained, FxHashMap and AHashMap are aliases of the stdlib’s hashmap with custom hashers.

Categories: rust Tags: , , ,

[Nim] A URL shortener command-line app.

October 23, 2018 Leave a comment

This afternoon I wrote a URL shortener command-line application in Nim. It uses the URL shortener service.

You can find the project here: .

Categories: nim Tags: , , , Share and discover the best programming tutorials and courses online

April 7, 2015 Leave a comment

Here you can find a nice collection of programming tutorials.

Categories: Uncategorized Tags: ,

black magic: 0x5f3759df

April 5, 2013 Leave a comment

The number 0x5f3759df is a magic constant that can be used to calculate the inverse square root of a number very efficiently. See this post for a detailed explanation. Now if you come across this number (which can happen anywhere, anytime), you will say “aha, I know that one”.

Programming, Motherfucker!

June 15, 2012 Leave a comment

We are a community of motherfucking programmers who have been humiliated by software development methodologies for years. We are tired of XP, Scrum, Kanban, Waterfall, Software Craftsmanship (aka XP-Lite) and anything else getting in the way of…Programming, Motherfucker.

reddit discussion

Categories: fun Tags:

List of freely available programming books

June 14, 2012 Leave a comment
Categories: Uncategorized Tags: , ,

brute force

April 13, 2012 Leave a comment

When in doubt, use brute force.” — Ken Thompson

Eh :)