Struct EpsilonGreedy 

pub struct EpsilonGreedy { /* private fields */ }

Available on crate feature bandit only.

Epsilon-Greedy multi-armed bandit.

With probability epsilon, selects a random arm; otherwise selects the arm with the highest observed mean reward. Supports optional epsilon decay.

Examples

use rill_ml::bandit::{Bandit, EpsilonGreedy, EpsilonGreedyConfig};
use rand::SeedableRng;
use rand_chacha::ChaCha8Rng;

let mut rng = ChaCha8Rng::seed_from_u64(0);
let mut bandit = EpsilonGreedy::new(3, EpsilonGreedyConfig::default()).unwrap();

let arm = bandit.select(&mut rng).unwrap();
bandit.update(arm, 1.0).unwrap();
assert_eq!(bandit.samples_seen(), 1);

Implementations

impl EpsilonGreedy

pub fn new( arm_count: usize, config: EpsilonGreedyConfig, ) -> Result<Self, RillError>

Create a new epsilon-greedy bandit.

Errors

Returns RillError::InvalidArmCount if arm_count is zero. Returns RillError::InvalidEpsilon if epsilon is not in [0, 1]. Returns RillError::InvalidParameter if decay is not in (0, 1].

pub const fn current_epsilon(&self) -> f64

The current (possibly decayed) epsilon value.

pub fn pulls(&self) -> &[u64]

Per-arm pull counts (diagnostic).

pub fn total_rewards(&self) -> &[f64]

Per-arm total rewards (diagnostic).

pub fn validate(&self) -> Result<(), RillError>

Validate all persisted state invariants.

This is also run automatically during deserialization.

Trait Implementations

impl Bandit for EpsilonGreedy

fn arm_count(&self) -> usize

The number of arms (actions) available.

fn samples_seen(&self) -> u64

How many total samples (arm pulls) the bandit has observed.

fn select(&self, rng: &mut impl Rng) -> Result<usize, RillError>

Select an arm using the provided RNG for exploration.

fn update(&mut self, arm: usize, reward: f64) -> Result<(), RillError>

Update the bandit with the observed reward for a previously selected arm.

fn reset(&mut self)

Reset the bandit to its initial (no-data) state.

fn arm_stats(&self, arm: usize) -> Result<ArmStats, RillError>

Per-arm diagnostic statistics.

impl Clone for EpsilonGreedy

fn clone(&self) -> EpsilonGreedy

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for EpsilonGreedy

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

Formats the value using the given formatter.