Manuel Raimann
47b5f9cec8
- Add blanket `impl Objective<V> for Fn(&mut Trial) -> Result<V, E>` so closures work directly with `optimize` - Rewrite optimize, optimize_async, optimize_parallel to accept `impl Objective<V>` with before_trial/after_trial hooks - Remove optimize_with, optimize_with_async, optimize_with_parallel - Remove max_retries and retry logic from Objective trait - Add explicit closure type annotations for HRTB inference - Convert FnMut test closures to Fn via RefCell/Cell
59 lines
1.5 KiB
Rust
59 lines
1.5 KiB
Rust
//! Early stopping — halt an entire study once a target is reached.
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//!
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//! Implements the [`Objective`] trait on a custom struct and uses the
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//! [`after_trial`](Objective::after_trial) hook to return
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//! `ControlFlow::Break(())` when the best value drops below a threshold.
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//!
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//! Run with: `cargo run --example early_stopping`
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use std::ops::ControlFlow;
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use optimizer::prelude::*;
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/// An objective that minimises `(x - 3)^2` and stops early once the
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/// value drops below `target`.
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struct EarlyStopObjective {
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x: FloatParam,
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target: f64,
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}
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impl Objective<f64> for EarlyStopObjective {
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type Error = Error;
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fn evaluate(&self, trial: &mut Trial) -> Result<f64> {
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let v = self.x.suggest(trial)?;
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Ok((v - 3.0).powi(2))
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}
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fn after_trial(&self, _study: &Study<f64>, trial: &CompletedTrial<f64>) -> ControlFlow<()> {
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if trial.value < self.target {
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println!("Target {} reached at trial #{}", self.target, trial.id);
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ControlFlow::Break(())
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} else {
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ControlFlow::Continue(())
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}
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}
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}
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fn main() -> optimizer::Result<()> {
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let study: Study<f64> = Study::new(Direction::Minimize);
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let x = FloatParam::new(-10.0, 10.0).name("x");
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let objective = EarlyStopObjective {
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x: x.clone(),
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target: 0.01,
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};
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study.optimize(100, objective)?;
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let best = study.best_trial()?;
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println!(
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"Stopped after {} trials — best f({:.4}) = {:.6}",
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study.n_trials(),
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best.get(&x).unwrap(),
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best.value,
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);
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Ok(())
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}
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