The choice of initial learning rate can have a profound effect on the performance of deep networks. We present a class of neural networks with solvable training dynamics, and confirm their predictions empirically in practical deep learning settings. The networks exhibit sharply distinct behaviors at small and large learning rates. The two regimes are separated by a phase transition. In the small learning rate phase, training can be understood using the existing theory of infinitely wide neural networks. At large learning rates the model captures qualitatively distinct phenomena, including the convergence of gradient descent dynamics to flatter minima. One key prediction of our model is a narrow range of large, stable learning rates. We find good agreement between our model's predictions and training dynamics in realistic deep learning settings. Furthermore, we find that the optimal performance in such settings is often found in the large learning rate phase. We believe our results shed light on characteristics of models trained at different learning rates. In particular, they fill a gap between existing wide neural network theory, and the nonlinear, large learning rate, training dynamics relevant to practice.

本文研究了学习速率对深度神经网络性能的影响，提出了一种具有可解训练动态的神经网络类，并在实际深度学习环境中验证了其预测，发现小学习率相当于传统理论下的无穷宽神经网络，而大学习率相当于梯度下降动态收敛到更平坦的极小值点，模型中预测的大而稳定的学习率范围得到了验证，同时发现在大学习率下模型性能优越。

深度学习的大学习率阶段: 弹射机制