Unleashing the Potential of Acquisition Functions in High-Dimensional Bayesian Optimization

Abstract

Bayesian optimization (BO) is widely used to optimize expensive-to-evaluate black-box functions. It first builds a surrogate for the objective and quantifies its uncertainty. It then decides where to sample by maximizing an acquisition function (AF) defined by the surrogate model. However, when dealing with high-dimensional problems, finding the global maximum of the AF becomes increasingly challenging. In such cases, the manner in which the AF maximizer is initialized plays a pivotal role. An inappropriate initialization can severely limit the potential of AF. This paper investigates a largely understudied problem concerning the impact of AF maximizer initialization on exploiting AFs' capability. Our large-scale empirical study shows that the widely used random initialization strategy may fail to harness the potential of an AF. Based on this observation, we propose a better initialization approach by employing multiple heuristic optimizers to leverage the historical data of black-box optimization to generate initial points for an AF maximizer. We evaluate our approach with a variety of heavily studied synthetic test functions and real-world applications. Experimental results show that our techniques, while simple, can significantly enhance the standard BO and outperform state-of-the-art methods by a large margin in most test cases.