A General Framework for User-Guided Bayesian Optimization
Carl Hvarfner, Frank Hutter, Luigi Nardi

TL;DR
This paper introduces ColaBO, a flexible Bayesian optimization framework that allows users to incorporate prior knowledge, improving efficiency when the prior is accurate and maintaining robustness when it is not.
Contribution
ColaBO is the first Bayesian framework enabling incorporation of diverse prior beliefs beyond kernel structures, applicable across various acquisition functions.
Findings
ColaBO accelerates optimization with accurate priors.
It maintains default performance with misleading priors.
The framework is broadly applicable across different beliefs and acquisition functions.
Abstract
The optimization of expensive-to-evaluate black-box functions is prevalent in various scientific disciplines. Bayesian optimization is an automatic, general and sample-efficient method to solve these problems with minimal knowledge of the underlying function dynamics. However, the ability of Bayesian optimization to incorporate prior knowledge or beliefs about the function at hand in order to accelerate the optimization is limited, which reduces its appeal for knowledgeable practitioners with tight budgets. To allow domain experts to customize the optimization routine, we propose ColaBO, the first Bayesian-principled framework for incorporating prior beliefs beyond the typical kernel structure, such as the likely location of the optimizer or the optimal value. The generality of ColaBO makes it applicable across different Monte Carlo acquisition functions and types of user beliefs. We…
Peer Reviews
Decision·ICLR 2024 spotlight
The framework's adaptability and flexibility to incorporate prior knowledge into the optimization process. The method maintains reasonable performance even when the prior knowledge is misleading, demonstrating its robustness in different scenarios.
Test functions used to evaluate the proposed framework were quite limited, only a restricted set of test functions was employed.
1. The paper considers a novel black-box optimization setting where good prior knowledge exists and proposes a framework to handle this problem. 2. Based on sampling, this framework is compatible with all Monte Carlo acquisition functions. 3. With acquisitions to be Log Expected Improvement and Max-Value Entropy Search, the proposed models work well in synthetic and hyperparameter tuning tasks when well-located prior to the optimal location is available, while the drop in performance is not obvi
1. Although the empirical performance of ColaBO looks promising in the synthetic task and hyperparameter tuning task, the theory developed in the work is limited. Therefore, how the method performs statistically is a concern, given that there are many approximations, such as the Monte Carlo acquisition and the RFF sampling. 2. The empirical section can be further enhanced by testing the algorithms on more challenging tasks, for example, higher-dimensional problems. The paper primarily focuses on
* The proposed technique is original and interesting. It certainly appears more principled than previous approaches to incorporating expert knowledge.
* The mathematical derivation is too informal in some places, affecting clarity. I believe this needs to be improved. For instance, $\pi$ here represents a belief over functions. Then why is Eq. (4) a function that receives a point $x \in \mathcal{X}$? Shouldn't it be a probability distribution over functions? Also, Def 3.1 introduces a conditioning on $\pi$. I found this quite confusing. Is $\pi$ a density? a function? or a random variable? * There are concerns about the fairness of the experim
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Taxonomy
TopicsMachine Learning and Data Classification · Advanced Bandit Algorithms Research · Advanced Multi-Objective Optimization Algorithms
