An acquisition function ranks untried hyperparameter combinations by their promise and uncertainty, guiding the next objective evaluation in Bayesian optimization. section 6.3.4
It balances exploration of uncertain regions with exploitation of combinations expected to improve model performance. A surrogate function supplies the estimates and is updated from objective feedback. section 6.3.4
Optuna hyperparameter search
An Optuna study searches XGBoost settings such as learning rate, estimators, subsampling, depth, and regularization, then records the best parameters and objective value.


