Struct AdcLut 

pub struct AdcLut {
    pub subspace_count: u16,
    pub centroids_per_subspace: u16,
    pub table: Vec<f32>,
}

Asymmetric Distance Computation lookup table — used by codecs that pre-decompose the query into per-subspace distance tables (PQ, IVF-PQ, TurboQuant). Consumed by base-layer rerank kernels via AVX2 pshufb or AVX-512 vpermb.

Layout:

• subspace_count: number of independent subspaces (PQ M parameter)
• centroids_per_subspace: typically 256 (one byte per code)
• table: row-major [subspace][centroid] -> f32 distance

Fields

subspace_count: u16

centroids_per_subspace: u16

table: Vec<f32>

Implementations

impl AdcLut

pub fn new(subspace_count: u16, centroids_per_subspace: u16) -> Self

pub fn lookup(&self, subspace: u16, centroid: u8) -> f32

Return the precomputed distance for the given subspace and centroid.

Panics

Panics if subspace >= self.subspace_count or centroid as usize >= self.centroids_per_subspace as usize. Bounds checking is the caller’s responsibility on this hot-path accessor.