Gradient Descent with Early Stopping is Provably Robust to Label Noise for Overparameterized Neural Networks

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Mingchen Li, Mahdi Soltanolkotabi, Samet Oymak ;
Proceedings of the Twenty Third International Conference on Artificial Intelligence and Statistics, PMLR 108:4313-4324, 2020.

Abstract

Modern neural networks are typically trained in an over-parameterized regime where the parameters of the model far exceed the size of the training data. Such neural networks in principle have the capacity to (over)fit any set of labels including significantly corrupted ones. Despite this (over)fitting capacity in this paper we demonstrate that such overparameterized networks have an intriguing robustness capability: they are surprisingly robust to label noise when first order methods with early stopping is used to train them. This paper also takes a step towards demystifying this phenomena. Under a rich dataset model, we show that gradient descent is provably robust to noise/corruption on a constant fraction of the labels. In particular, we prove that: (i) In the first few iterations where the updates are still in the vicinity of the initialization gradient descent only fits to the correct labels essentially ignoring the noisy labels. (ii) To start to overfit to the noisy labels network must stray rather far from the initialization which can only occur after many more iterations. Together, these results show that gradient descent with early stopping is provably robust to label noise and shed light on the empirical robustness of deep networks as well as commonly adopted heuristics to prevent overfitting.

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