[question] How to configure the stdlib to be fast? about hashbrown HOT 8 CLOSED

You can use FxHashMap or AHashMap which are aliases of the libstd hashmap with custom hashers. They can be found in the ahash and rustc-hash crates.

from hashbrown.

Thanks @Amanieu . I also found https://crates.io/crates/fxhash , which seems to be the same as https://crates.io/crates/rustc-hash . Which one to use?

I could try FxHashMap since I found examples for it. However, AHashMap doesn't provide any code snippets. How could I try it? Do you have an example for it?

from hashbrown.

AHashMap is used exactly the same way as FxHashMap.

from hashbrown.

For FxHashMap, this works:

use rustc_hash::FxHashMap;
let map: FxHashMap<u32, u32> = FxHashMap::default();

I tried this with ahash but had no luck:

use ahash::AHashMap;
let map: AHashMap<u32, u32> = AHashMap::default();

from hashbrown.

Try AHashMap::new instead.

from hashbrown.

I get this error:

2 | use ahash::AHashMap as HashMap;
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^ no `AHashMap` in the root

Cargo.toml is OK:

[dependencies]    
ahash = "0.2"

from hashbrown.

You need to enable the std feature in Cargo.toml:

ahash = {version = "0.2", features = ["std"]}

from hashbrown.

Thanks @Amanieu , it works now!

from hashbrown.