Activation Density driven Energy-Efficient Pruning in Training

The process of neural network pruning with suitable fine-tuning and retraining can yield networks with considerably fewer parameters than the original with comparable degrees of accuracy. Typically, pruning methods require large, pre-trained networks as a starting point from which they perform a time-intensive iterative pruning and retraining algorithm. We propose a novel pruning in-training method that prunes a network real-time during training, reducing the overall training time to achieve an optimal compressed network. To do so, we introduce an activation density based analysis that identifies the optimal relative sizing or compression for each layer of the network. Our method removes the need for pre-training and is architecture agnostic, allowing it to be employed on a wide variety of systems. For VGG-19 and ResNet18 on CIFAR-10, CIFAR-100, and TinyImageNet, we obtain exceedingly sparse networks (up to 200x reduction in parameters and >60x reduction in inference compute operations in the best case) with comparable accuracies (up to 2%-3% loss with respect to the baseline network). By reducing the network size periodically during training, we achieve total training times that are shorter than those of previously proposed pruning methods. Furthermore, training compressed networks at different epochs with our proposed method yields considerable reduction in training compute complexity (1.6x -3.2x lower) at near iso-accuracy as compared to a baseline network trained entirely from scratch.