Are Saddles Good Enough for Deep Learning?
This work addresses a fundamental optimization problem in deep learning for researchers and practitioners, offering a novel perspective that could influence gradient descent methods.
The paper challenges the conventional wisdom that deep neural networks converge to local minima, proposing instead that they converge to highly degenerate saddle points ('good saddles'), supported by experiments on MNIST and CIFAR-10 datasets.
Recent years have seen a growing interest in understanding deep neural networks from an optimization perspective. It is understood now that converging to low-cost local minima is sufficient for such models to become effective in practice. However, in this work, we propose a new hypothesis based on recent theoretical findings and empirical studies that deep neural network models actually converge to saddle points with high degeneracy. Our findings from this work are new, and can have a significant impact on the development of gradient descent based methods for training deep networks. We validated our hypotheses using an extensive experimental evaluation on standard datasets such as MNIST and CIFAR-10, and also showed that recent efforts that attempt to escape saddles finally converge to saddles with high degeneracy, which we define as `good saddles'. We also verified the famous Wigner's Semicircle Law in our experimental results.