Struct SearchKnobs 

pub struct SearchKnobs {
    pub prefetch: u8,
    pub batch_est: bool,
    pub frontier: f32,
    pub block_screen: bool,
    pub rerank_z: f32,
}

Runtime knobs of the search loop, each off by default so that the results are those of the plain search. VGraph::searcher reads them once per process from the environment (SearchKnobs::from_env); VGraph::searcher_with takes them explicitly.

Mechanisms, and what they may change:

• prefetch (WARM_QGRAPH_PREFETCH, 0..=3, results never change): 0 prefetches the next candidate’s neighbour list, the code row and estimate terms (scale, Euclidean norm) of every admitted neighbour, and the rows the re-rank reads; 2 adds the neighbour list of the second-nearest unexpanded candidate; 3 adds a lookahead that, after an expansion, prefetches the code rows (or screen rows) of the next candidate’s unvisited neighbours.
• batch_est (WARM_QGRAPH_BATCH_EST, results never change): the admitted neighbours’ 4-bit rows are estimated four at a time with shared query loads (dot_i4_inline_x4 in the kernels module); the integer sums are the same.
• frontier (WARM_QGRAPH_FRONTIER, 0.0..=1.0, 1.0 = off): with a full pool, stop when the nearest unexpanded estimate is past the point frontier of the way from the k-th best to the ef-th best. Fewer expansions, so lower recall at a given ef; the recall/QPS curve over ef is what to compare.
• block_screen (WARM_QGRAPH_BLOCK_SCREEN, needs VGraph::with_blocks): the neighbour block screens instead of ordering; survivors fetch their code row and the pool holds row estimates, as in the plain search. A fresh neighbour is skipped when its block estimate, improved by screen_sigmas deviations of the calibrated edge error, could not enter the full pool. Off, the block search is the existing one.

Fields

prefetch: u8

Prefetch depth, 0 to 3 (values above 3 act as 3).

batch_est: bool

Estimate admitted neighbours four rows at a time.

frontier: f32

Frontier stop fraction in 0.0..=1.0; 1.0 (or a non-finite value) is off.

block_screen: bool

Screen with the neighbour blocks and estimate survivors from their rows.

rerank_z: f32

Bound-gated re-rank: with z > 0, candidates are re-scored in estimate order and the re-rank stops at the first whose estimate, corrected by the mean error and lowered by z standard deviations (both measured on this query’s re-scored rows), cannot beat the current k-th exact distance. rerank stays the cap. 0 (or non-finite) is off.

Implementations

impl SearchKnobs

pub const OFF: Self

Every knob off: the plain search.

pub fn from_env() -> Self

The knobs set in the environment, read once per process; unset or invalid values (reported once) take the SearchKnobs::OFF value.

Trait Implementations

impl Clone for SearchKnobs

fn clone(&self) -> SearchKnobs

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for SearchKnobs

impl Debug for SearchKnobs

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

Formats the value using the given formatter.

impl Default for SearchKnobs

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for SearchKnobs

fn eq(&self, other: &SearchKnobs) -> bool

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for SearchKnobs