Struct HyperbandPruner 

pub struct HyperbandPruner { /* private fields */ }

Asynchronous Hyperband: a fan of AshaPruner brackets over one ladder.

The bracket schedule

From (min_resource, max_resource, reduction_factor η) the number of brackets is s_max + 1, where s_max = floor(log_η(max / min)) is the most aggressive bracket whose first rung still fits under the maximum. Bracket s is an AshaPruner over the sub-ladder starting at min · ηˢ:

Bracket s	First rung	Character
0	min	most rungs — aggressive early stopping, exploration
…	min · ηˢ	fewer rungs
s_max	min · η^{s_max}	one rung near the top — little pruning, exploitation

Bracket assignment

bracket_of(study, trial_number, n_brackets) — crc32(study ‖ trial_number) mod n_brackets. It is a pure function of identifiers every worker already has, so no bracket-assignment table is shared or persisted: two processes place the same trial in the same bracket by computing it, never by coordinating.

Promotion within a bracket

Identical to AshaPruner, with the rung’s occupants filtered to the trials in the same bracket (each trial’s bracket is recomputed with the same pure function). A multi-objective study is never pruned; NaN at a rung is pruned.

Determinism

Bracket assignment is pre-determined (a pure function of (study, number)), but the promotion decision, like AshaPruner’s, reads the ask-time StudyView and so depends on which same-bracket trials had filled the rung — replayable, not pre-determined, under parallelism (where determinism stops). Single-worker with a fixed seed is fully reproducible.

use atune_core::scheduler::HyperbandPruner;

// η = 3, from 1 to 27: brackets start at 1, 3, 9, 27 -> 4 brackets.
let hb = HyperbandPruner::new(1, 27, 3)?;
assert_eq!(hb.brackets(), 4);

Implementations

impl HyperbandPruner

pub fn new( min_resource: u64, max_resource: u64, reduction_factor: u32, ) -> Result<Self>

Builds a Hyperband pruner over (min_resource, max_resource, reduction_factor).

Errors

Error::InvalidSpace for a nonsense ladder — see RungLadder::new.

pub fn with_default_eta(min_resource: u64, max_resource: u64) -> Result<Self>

Builds a Hyperband pruner with the default reduction factor.

Errors

As new.

pub fn with_objective(self, obj: usize) -> Self

Selects which objective dimension to gate on (default 0), propagating it to every bracket.

pub fn brackets(&self) -> u32

The number of brackets.

pub const fn min_resource(&self) -> u64

The first rung’s resource.

pub const fn max_resource(&self) -> u64

The finish line.

pub const fn reduction_factor(&self) -> u32

The geometric factor η.

pub fn bracket_for(&self, view: &StudyView, number: TrialNumber) -> u32

The bracket a trial is assigned to.

Trait Implementations

impl Clone for HyperbandPruner

fn clone(&self) -> HyperbandPruner

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for HyperbandPruner

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

Formats the value using the given formatter.

impl Scheduler for HyperbandPruner

fn on_report( &self, study: &StudyView, trial: &TrialMeta, step: u64, values: &[f64], ) -> Result<Decision>

Assigns the trial to its bracket and applies that bracket’s ASHA rule against the same-bracket occupants; see the type docs.

Errors

Never — the decision is total.

fn state(&self) -> Result<Option<SchedulerState>>

None: bracket assignment is a pure function and rung tables are derived from the StudyView — nothing to persist.

fn fan_report_mode(&self) -> FanReportMode

Declares whether this scheduler accepts aligned aggregate fan reports.

fn scripted_capability(&self) -> ScriptedSchedulerCapability

Declares whether scripted ask/tell can recreate this scheduler.

fn on_trial_end( &self, study: &StudyView, trial: &FrozenTrial, ) -> Result<Vec<Command>>

Called once a trial reaches a terminal state.

fn resume_candidates(&self, study: &StudyView) -> Result<Vec<Command>>

Paused trials worth waking on a freed work slot, in priority order.

fn restore_state(&self, blob: &SchedulerState) -> Result<()>

Restores a scheduler from a previously persisted blob.