//! Various CPU-based indices that run on the raw vectors. Leverage SIMD under
//! the hood.
//!
//! Provides:
//!
//! - Two tree-based versions: Annoy (memory-based) and BallTree.
//! - Two clustering-based versions: IVF and LSH (multi-probe) version
//! - Three graph-based versions: Vanama (memory-based version), HNSW and
//! NNDescent
//!
//! And a flat exhaustive version