Title
Catastrophic Fisher Explosion: Early Phase Fisher Matrix Impacts Generalization
Abstract
The early phase of training a deep neural network has a dramatic effect on the local curvature of the loss function. For instance, using a small learning rate does not guarantee stable optimization because the optimization trajectory has a tendency to steer towards regions of the loss surface with increasing local curvature. We ask whether this tendency is connected to the widely observed phenomenon that the choice of the learning rate strongly influences generalization. We first show that stochastic gradient descent (SGD) implicitly penalizes the trace of the Fisher Information Matrix (FIM), a measure of the local curvature, from the start of training We argue it is an implicit regularizer in SGD by showing that explicitly penalizing the trace of the FIM can significantly improve generalization. We highlight that poor final generalization coincides with the trace of the FIM attaining a large value early in training, to which we refer as catastrophic Fisher explosion. Finally, to gain insight into the regularization effect of penalizing the trace of the FIM, we show that it limits memorization by reducing the learning speed of examples with noisy labels more than that of the examples with clean labels.
Year
Venue
DocType
2021
INTERNATIONAL CONFERENCE ON MACHINE LEARNING, VOL 139
Conference
Volume
ISSN
Citations 
139
2640-3498
0
PageRank 
References 
Authors
0.34
0
9
Name
Order
Citations
PageRank
Jastrzębski Stanisław113114.12
Devansh Arpit214614.24
Oliver Astrand300.34
Giancarlo Kerg421.71
Huan Wang500.34
Caiming Xiong696969.56
Richard Socher76770230.61
Kyunghyun Cho86803316.85
Krzysztof Geras9757.45