Struct SuccessiveHalvingPruner 

pub struct SuccessiveHalvingPruner { /* private fields */ }

ASHA-style (Asynchronous Successive Halving) pruner — the “advanced” option.

Trials are compared at a ladder of resource rungs min_resource * reduction_factor^k (starting at exponent min_early_stopping_rate). When a trial crosses a rung, only the top 1/reduction_factor fraction of the trials that reached that rung are promoted to continue; the rest are pruned. Compared to [MedianPruner], this allocates a shrinking budget across rungs rather than a single median cut, and is asynchronous (each trial is judged against whichever peers have reached its rung so far), which suits parallel execution.

Implemented second and treated as the advanced choice; [MedianPruner] is the simpler default.

Implementations

impl SuccessiveHalvingPruner

pub fn new() -> SuccessiveHalvingPruner

Defaults: min_resource = 1, reduction_factor = 4, min_early_stopping_rate = 0.

pub fn min_resource(self, r: usize) -> SuccessiveHalvingPruner

Resource (step count) of the first rung.

pub fn reduction_factor(self, eta: usize) -> SuccessiveHalvingPruner

eta: the fraction 1/eta of trials promoted at each rung, and the factor by which rung resources grow. Must be >= 2.

pub fn min_early_stopping_rate(self, s: u32) -> SuccessiveHalvingPruner

Starting rung exponent — skip the earliest, cheapest rungs.

Trait Implementations

impl Clone for SuccessiveHalvingPruner

fn clone(&self) -> SuccessiveHalvingPruner

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SuccessiveHalvingPruner

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

Formats the value using the given formatter.

impl Default for SuccessiveHalvingPruner

fn default() -> SuccessiveHalvingPruner

Returns the “default value” for a type.

impl Pruner for SuccessiveHalvingPruner

fn should_prune(&self, study_state: &StudyState, trial: &Trial) -> bool