Google Research

Disentangling sampling and labeling bias for learning in large-output spaces

International Conference on Machine Learning (ICML) 2021 (to appear)

Abstract

Negative sampling is a widely adopted technique to enable efficient training in settings with a large number of classes. Typically, negative sampling approaches aim at approximating the value or gradient of the computationally expensive loss function that takes all the negative labels into account. In this work, we study the connection between negative sampling approaches and loss modification techniques for countering label imbalance. We show that different (bias) correction strategies that accompany negative sampling approaches can have unintended consequences on the model's performance on various data sub-populations. We then propose a unified approach to tackle both sampling bias, arising from working with a subset of all negative classes, and labeling bias, which is inherently present in the data due to label-imbalance. Finally, we verify our analysis and demonstrate the utility of our unified approach through empirical evaluation on standard image classification and retrieval benchmarks.

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