In GB-BI, we follow the approach of BOP-Elites: every generation the algorithm only evaluates the candidate solution with the highest EI in each niche. In addition, we also explore the effectiveness of other acquisition functions as alternatives for EI. The most straightforward acquisition function we consider is the posterior mean, µ(x). We also consider the upper confidence bound (UCB) acquisition function, which is commonly used in multi-armed bandit problems and is defined as