Define the evaluation task
Specify the environment or logged dataset, the policy class, and the return definition (episodic or discounted).
Evaluate RL policies. Quantify expected returns.
Policy evaluation estimates the expected return of a policy under a given environment or dataset. Important challenges include off-policy corrections, variance reduction, reliable confidence intervals, and robust metrics such as regret and safety violation rates.
Learning concept · Not a validated service
Policy evaluation estimates the expected return of a policy under a given environment or dataset. Important challenges include off-policy corrections, variance reduction, reliable confidence intervals, and robust metrics such as regret and safety violation rates.
A proposed use is offline evaluation of new policies using logged simulator or trajectory data so engineers can compare expected returns before deployment; for safety-critical domains a human reviewer must keep final control and these prototypes are not production-ready.
Specify the environment or logged dataset, the policy class, and the return definition (episodic or discounted).
Start with a simple controlled simulator or bandit to validate metric calculation and seed management.
Compute average return, cumulative regret, and confidence intervals or bootstrap estimates for variance.
Add importance-sampling or model-based estimators and track stability across random seeds and dataset shifts.
The supplied starter simulates a 4-armed Bernoulli bandit and runs an epsilon-greedy action selection for 2000 steps. It maintains incremental sample means (estimated_values) and action counts, updates the chosen arm's estimated reward using a running average, and prints final action counts, estimated rates and total reward.
for step in range(1, 2001):
if rng.random() < epsilon:
action = rng.integers(len(true_reward_rates))
else:
action = int(np.argmax(estimated_values))
reward = 1 if rng.random() < true_reward_rates[action] else 0
action_counts[action] += 1
total_reward += reward
estimated_values[action] += (reward - estimated_values[action]) / action_counts[action]The starter is a small multi-armed bandit simulation, not a full RL policy evaluation on an environment with states, transitions or episodic returns. It lacks off-policy estimators, confidence intervals, regret calculations, multiple seeds, safety checks and any logging or dataset support that a production evaluation toolkit requires.
A proposed extension: replace the toy bandit with a Gymnasium environment or offline trajectory logs, add importance-sampling and model-based estimators, and produce average-return and regret reports with bootstrapped confidence intervals.
This is a potential application pathway, not a delivered product. The supplied starter does not implement this service or validate it with real users.
Networkers Home runs this topic inside its AI Engineer Course, with placement support and hands-on labs.