Active learning has been a main solution for reducing data labeling costs. However, existing active learning strategies assume that a data owner can interact with annotators in an online, timely manner, which is usually impractical. Even with such interactive annotators, for existing active learning strategies to be effective, they often require many rounds of interactions between the data owner and annotators, which is often time-consuming. In this work, we initiate the study of one-round active learning, which aims to select a subset of unlabeled data points that achieve the highest utility after being labeled with only the information from initially labeled data points. We propose DULO, a general framework for one-round active learning based on the notion of data utility functions, which map a set of data points to some performance measure of the model trained on the set. We formulate the one-round active learning problem as data utility function maximization. We further propose strategies to make the estimation and optimization of data utility functions scalable to large models and large unlabeled data sets. Our results demonstrate that while existing active learning approaches could succeed with multiple rounds, DULO consistently performs better in the one-round setting.
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