Struct SDCTable 

pub struct SDCTable<const M: usize, const NBITS: usize>
where
    [(); { _ }]:,
{ /* private fields */ }

Precomputed centroid-to-centroid distances for Symmetric Distance Computation (SDC).

SDC enables fast distance computation between two PQ codes without needing the original vectors. During quantizer training, we precompute squared L2 distances between all pairs of centroids in each subspace.

Table layout: table[m * ksub * ksub + i * ksub + j] is the squared distance between centroid i and centroid j in subspace m.

The const generics must match the ProductQuantizer configuration:

• M: number of subquantizers
• NBITS: bits per centroid index

Implementations

impl<const M: usize, const NBITS: usize> SDCTable<M, NBITS>

where [(); { _ }]:,

pub const KSUB: usize

Number of centroids per subspace (2^NBITS)

pub fn from_centroids(centroids: &[f32], dsub: usize) -> Self

Create an SDCTable from centroids using squared L2 distance.

Arguments

• centroids - Flat centroid storage: M * ksub * dsub floats
• dsub - Dimension of each subspace

pub fn from_centroids_with_distance( centroids: &[f32], dsub: usize, subspace_distance: impl Fn(&[f32], &[f32]) -> f32, ) -> Self

Create an SDCTable from centroids using a custom subspace distance function.

The distance function receives two subvector slices of length dsub and returns a non-negative distance value.

Arguments

• centroids - Flat centroid storage: M * ksub * dsub floats
• dsub - Dimension of each subspace
• subspace_distance - Distance function for subvector pairs

pub fn distance( &self, code1: &PQCode<M, NBITS>, code2: &PQCode<M, NBITS>, ) -> f32

Compute approximate squared L2 distance between two PQ codes.

This is the core of SDC: sum precomputed centroid-to-centroid distances for each subspace.

pub fn ksub(&self) -> usize

Number of centroids per subspace.

pub fn table_data(&self) -> &[f32]

Access the raw table data for serialization.

pub fn from_raw(table: Vec<f32>, ksub: usize) -> Self

Reconstruct an SDCTable from raw data.

Trait Implementations

impl<const M: usize, const NBITS: usize> Clone for SDCTable<M, NBITS>

where [(); { _ }]:,

fn clone(&self) -> SDCTable<M, NBITS>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<const M: usize, const NBITS: usize> Debug for SDCTable<M, NBITS>

where [(); { _ }]:,

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<const M: usize, const NBITS: usize> PartialEq for SDCTable<M, NBITS>

where [(); { _ }]:,

fn eq(&self, other: &SDCTable<M, NBITS>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<const M: usize, const NBITS: usize> StructuralPartialEq for SDCTable<M, NBITS>

where [(); { _ }]:,