## Gradient Descent on Neural Networks Typically Occurs at the Edge of Stability

28 Sep 2020 (modified: 05 Mar 2021)ICLR 2021 PosterReaders: Everyone
• Keywords: optimization, trajectory, stability, sharpness, implicit bias, implicit regularization, L-smoothness, deep learning theory, science of deep learning
• Abstract: We empirically demonstrate that full-batch gradient descent on neural network training objectives typically operates in a regime we call the Edge of Stability. In this regime, the maximum eigenvalue of the training loss Hessian hovers just above the value $2 / \text{(step size)}$, and the training loss behaves non-monotonically over short timescales, yet consistently decreases over long timescales. Since this behavior is inconsistent with several widespread presumptions in the field of optimization, our findings raise questions as to whether these presumptions are relevant to neural network training. We hope that our findings will inspire future efforts aimed at rigorously understanding optimization at the Edge of Stability.
• One-sentence Summary: We trained neural networks using full-batch gradient descent -- you won't believe what happens next!
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