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On the Importance of Feature Separability in Predicting Out-Of-Distribution Error

RENCHUNZI XIE · Hongxin Wei · Lei Feng · Yuzhou Cao · Bo An

Great Hall & Hall B1+B2 (level 1) #1610
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Tue 12 Dec 3:15 p.m. PST — 5:15 p.m. PST


Estimating the generalization performance is practically challenging on out-of-distribution (OOD) data without ground-truth labels. While previous methods emphasize the connection between distribution difference and OOD accuracy, we show that a large domain gap not necessarily leads to a low test accuracy. In this paper, we investigate this problem from the perspective of feature separability empirically and theoretically. Specifically, we propose a dataset-level score based upon feature dispersion to estimate the test accuracy under distribution shift. Our method is inspired by desirable properties of features in representation learning: high inter-class dispersion and high intra-class compactness. Our analysis shows that inter-class dispersion is strongly correlated with the model accuracy, while intra-class compactness does not reflect the generalization performance on OOD data. Extensive experiments demonstrate the superiority of our method in both prediction performance and computational efficiency.

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