title: Momentum Doesn't Change The Implicit Bias
abstract: The momentum acceleration technique is widely adopted in many optimization algorithms. However, the theoretical understanding on how the momentum affects the generalization performance of the optimization algorithms is still unknown. In this paper, we answer this question through analyzing the implicit bias of momentum-based optimization. We prove that both SGD with momentum and Adam converge to the $L_2$ max-margin solution for exponential-tailed loss, which is the same as vanilla gradient descent. 
  That means, these optimizers with momentum acceleration still converge to a model with low complexity, which provides guarantees on their generalization.  Technically, to overcome the difficulty brought by the error accumulation in analyzing the momentum, we construct new Lyapunov functions as a tool to analyze the gap between the model parameter and the max-margin solution.
authors: Bohan Wang Qi Meng Huishuai Zhang Ruoyu Sun Wei Chen Zhi-Ming Ma
hIndex: Ruoyu Sun 18