Struct Config 

pub struct Config {
    pub expansion_factor: f64,
    pub auto_rebuild: bool,
    pub rebuild_depth_threshold: usize,
    pub tombstone_ratio_threshold: f64,
    pub range_headroom: f64,
}

Configuration parameters for LearnedMap.

Fields

expansion_factor: f64

Expansion factor for node arrays.

Controls the ratio of array size to key count. A factor of 2.0 means the array is twice as large as the number of keys (50% gaps), leaving room for future inserts without conflicts.

Higher values reduce conflicts but use more memory.

Default: 2.0. Must be >= 1.0.

auto_rebuild: bool

Whether to automatically rebuild the tree after a threshold of inserts.

When enabled, the map periodically rebuilds with optimal FMCD model fitting to keep the tree shallow and lookups fast. The rebuild threshold is (len / 4).clamp(16, 10_000).

Default: true.

rebuild_depth_threshold: usize

Maximum subtree depth before a localized rebuild is triggered.

When an insert descends through more child nodes than this threshold, the inserting thread rebuilds the degraded subtree inline. Only applies when auto_rebuild is true. Set to usize::MAX to disable.

Default: 8.

tombstone_ratio_threshold: f64

Maximum tombstone ratio before a localized rebuild is triggered.

When a node’s tombstone count (slots nulled by remove) exceeds this fraction of its capacity, the removing thread rebuilds the parent subtree inline. Only applies when auto_rebuild is true.

Set to 1.0 to disable tombstone compaction.

Default: 0.5 (compact when >50% of slots are tombstones).

range_headroom: f64

Extra key range headroom for model fitting.

When greater than 0, the model covers (1 + range_headroom) times the actual key range, leaving space for keys beyond the current max. This prevents all out-of-range keys from clamping to the last slot.

The array size grows proportionally to maintain per-key slot density. Only applies during model fitting (bulk load and rebuild).

Default: 0.0 (no headroom). Root rebuilds internally use 1.0.

Implementations

impl Config

pub fn new() -> Self

Create a new configuration with default values.

pub fn expansion_factor(self, factor: f64) -> Self

Set the expansion factor.

Panics

Panics if factor < 1.0.

pub fn auto_rebuild(self, enabled: bool) -> Self

Enable or disable automatic rebuilds.

pub fn rebuild_depth_threshold(self, threshold: usize) -> Self

Set the maximum subtree depth before localized rebuild triggers.

pub fn tombstone_ratio_threshold(self, threshold: f64) -> Self

Set the tombstone ratio threshold for compaction.

Panics

Panics if threshold is not in (0.0, 1.0].

pub fn range_headroom(self, headroom: f64) -> Self

Set the key range headroom for model fitting.

Panics

Panics if headroom < 0.0.

Trait Implementations

impl Clone for Config

fn clone(&self) -> Config

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Config

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

Formats the value using the given formatter.

impl Default for Config

fn default() -> Self

Returns the “default value” for a type.