Struct HnswConfig 

pub struct HnswConfig {
    pub max_nb_connection: usize,
    pub ef_construction: usize,
    pub ef_search: usize,
    pub max_layer: usize,
    pub max_elements: usize,
}

Configuration for the HNSW vector index.

Controls the trade-off between index build time, memory usage, and search accuracy. The defaults are tuned for PulseDB’s target scale (10K-500K experiences per collective).

Tuning Guide

Use Case	M	ef_construction	ef_search
Low memory	8	100	30
Balanced	16	200	50
High recall	32	400	100

Fields

max_nb_connection: usize

Maximum bidirectional connections per node (M parameter).

Higher values improve recall but increase memory and build time. Each node stores up to M links, so memory per node is O(M). Default: 16

ef_construction: usize

Number of candidates tracked during index construction.

Higher values produce a better quality graph but slow down insertion. Rule of thumb: ef_construction >= 2 * max_nb_connection. Default: 200

ef_search: usize

Number of candidates tracked during search.

Higher values improve recall but increase search latency. Must be >= k (the number of results requested). Default: 50

max_layer: usize

Maximum number of layers in the skip-list structure.

Lower layers are dense, upper layers are sparse “express lanes.” Default 16 handles datasets up to ~1M vectors with M=16. Default: 16

max_elements: usize

Initial pre-allocated capacity (number of vectors).

The index grows beyond this automatically, but pre-allocation avoids reallocations for known workloads. Default: 10_000

Trait Implementations

impl Clone for HnswConfig

fn clone(&self) -> HnswConfig

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for HnswConfig

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

Formats the value using the given formatter.

impl Default for HnswConfig

fn default() -> Self

Returns the “default value” for a type.