A Hash Function Must Be Deterministic, Uniform, and Fast — FNV-1a Is One Example

A hash function takes an arbitrary value and outputs a fixed-size integer. Requirements: deterministic, uniform distribution, fast. One common implementation is FNV-1a:

pub trait Hashable {
    fn hash(&self) -> u32;
}
 
impl Hashable for String {
    fn hash(&self) -> u32 {
        let mut hash = 2166136261;
        for c in self.as_bytes() {
            hash = (hash ^ (*c as u32)).wrapping_mul(16777619);
        }
        hash
    }
}

References

• https://craftinginterpreters.com/hash-tables.html#open-addressing

See also

• SimHash - h(x) = sign(wᵀx) — a hash function designed specifically to preserve cosine similarity, rather than distribute uniformly