Enhancing High-dimensional Bayesian Optimization by Optimizing the Acquisition Function Maximizer Initialization
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Bayesian optimization (BO) is widely used to optimize black-box functions. It works by first building a surrogate for the objective and quantifying the uncertainty in that surrogate. It then decides where to sample by maximizing an acquisition function defined by the surrogate model. Prior approaches typically use randomly generated raw samples to initialize the acquisition function maximizer. However, this strategy is ill-suited for high-dimensional BO. Given the large regions of high posterior uncertainty in high dimensions, a randomly initialized acquisition function maximizer is likely to focus on areas with high posterior uncertainty, leading to overly exploring areas that offer little gain. This paper provides the first comprehensive empirical study to reveal the importance of the initialization phase of acquisition function maximization. It proposes a better initialization approach by employing multiple heuristic optimizers to leverage the knowledge of already evaluated samples to generate initial points to be explored by an acquisition function maximizer. We evaluate our approach on widely used synthetic test functions and real-world applications. Experimental results show that our techniques, while simple, can significantly enhance the standard BO and outperforms state-of-the-art high-dimensional BO techniques by a large margin in most test cases.
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