  In this paper, we propose a novel progressive parameter pruning method for
Convolutional Neural Network acceleration, named Structured Probabilistic
Pruning (SPP), which effectively prunes weights of convolutional layers in a
probabilistic manner. Unlike existing deterministic pruning approaches, where
unimportant weights are permanently eliminated, SPP introduces a pruning
probability for each weight, and pruning is guided by sampling from the pruning
probabilities. A mechanism is designed to increase and decrease pruning
probabilities based on importance criteria in the training process. Experiments
show that, with 4x speedup, SPP can accelerate AlexNet with only 0.3% loss of
top-5 accuracy and VGG-16 with 0.8% loss of top-5 accuracy in ImageNet
classification. Moreover, SPP can be directly applied to accelerate
multi-branch CNN networks, such as ResNet, without specific adaptations. Our 2x
speedup ResNet-50 only suffers 0.8% loss of top-5 accuracy on ImageNet. We
further show the effectiveness of SPP on transfer learning tasks.
