Read the Signs: Towards Invariance to Gradient Descent's Hyperparameter Initialization

TL;DR

ActiveLR is a meta algorithm that dynamically adjusts learning rates based on gradient sign changes, improving training efficiency, robustness, and generalization across various models and datasets.

Contribution

It introduces ActiveLR, a novel meta algorithm that localizes and adapts learning rates during training based on gradient sign changes, reducing hyperparameter tuning.

Findings

Increases generalizability and training set fit.

Reduces training time across multiple datasets and models.

Mitigates negative effects of large mini-batch sizes.

Abstract

We propose ActiveLR, an optimization meta algorithm that localizes the learning rate, $\alpha$, and adapts them at each epoch according to whether the gradient at each epoch changes sign or not. This sign-conscious algorithm is aware of whether from the previous step to the current one the update of each parameter has been too large or too small and adjusts the $\alpha$ accordingly. We implement the Active version (ours) of widely used and recently published gradient descent optimizers, namely SGD with momentum, AdamW, RAdam, and AdaBelief. Our experiments on ImageNet, CIFAR-10, WikiText-103, WikiText-2, and PASCAL VOC using different model architectures, such as ResNet and Transformers, show an increase in generalizability and training set fit, and decrease in training time for the Active variants of the tested optimizers. The results also show robustness of the Active variant of these optimizers to different values of the initial learning rate. Furthermore, the detrimental effects of using large mini-batch sizes are mitigated. ActiveLR, thus, alleviates the need for hyper-parameter search for two of the most commonly tuned hyper-parameters that require heavy time and computational costs to pick. We encourage AI researchers and practitioners to use the Active variant of their optimizer of choice for faster training, better generalizability, and reducing carbon footprint of training deep neural networks.