In this work, we provide a characterization of the feature-learning process in two-layer ReLU networks trained by gradient descent on the logistic loss following random initialization. We consider data with binary labels that are generated by an XOR-like function of the input features. We permit a constant fraction of the training labels to be corrupted by an adversary. We show that, although linear classifiers are no better than random guessing for the distribution we consider, two-layer ReLU networks trained by gradient descent achieve generalization error close to the label noise rate, refuting the conjecture of Malach and Shalev-Shwartz that 'deeper is better only when shallow is good'. We develop a novel proof technique that shows that at initialization, the vast majority of neurons function as random features that are only weakly correlated with useful features, and the gradient descent dynamics 'amplify' these weak, random features to strong, useful features.

本文探讨了二层ReLU神经网络梯度下降训练过程中的特征学习，研究了使用XOR函数生成的带标签二进制数据，对一定比例的训练标签的干扰具有影响。我们证明了线性分类器并不比随机猜测的效果更好，而使用梯度下降训练二层ReLU神经网络可以达到接近噪声率的泛化误差。我们提出了一种新的证明技术，证明了在初始化时，绝大多数神经元都具有随机特征的性质，与有用特征之间的相关性较弱，而梯度下降动态将这些弱随机特征“放大”为强有用特征。

神经网络中的特征学习和泛化：随机特征增强