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A Univariate Bound of Area Under ROC
Proceedings of the 34th Conference on Uncertainty in Artificial Intelligence, PMLR R16:42-51, 2018.
Abstract
Area under ROC (AUC) is an important met- ric for binary classification and bipartite rank- ing problems. However, it is difficult to di- rectly optimize AUC as a learning objective, so most existing algorithms are based on optimiz- ing a surrogate loss to AUC. One significant drawback of these surrogate losses is that they require pairwise comparisons among training data, which leads to slow running time and in- creasing local storage for online learning. In this work, we describe a new surrogate loss based on a reformulation of AUC risk, which does not require pairwise comparison but rank- ings of the predictions. We further show that the ranking operation can be avoided, and the learning objective obtained based on this sur- rogate enjoys linear complexity in time and storage. We perform experiments to demon- strate the effectiveness of the online and batch algorithms for AUC optimization based on the proposed surrogate loss.