Succinct Network Channel and Spatial Pruning via Discrete Variable QCQP
Authors: Yeonwoo Jeong, Deokjae Lee, Gaon An, Changyong Son, Hyun Oh Song
Keywords: Network Pruning, Channel pruning, Spatial pruning, Network Compression, MIQCQP, Specified target resource constraint
Abstract:     Reducing the heavy computational cost of large convolutional neural networks is crucial when deploying the networks to resource-constrained environments. In this context, recent works propose channel pruning via greedy channel selection to achieve practical acceleration and memory footprint reduction. We first show this channel-wise approach ignores the inherent quadratic coupling between channels in the neighboring layers and cannot safely remove inactive weights during the pruning procedure. Furthermore, we show that these pruning methods cannot guarantee the given resource constraints are satisfied and cause discrepancy with the true objective. To this end, we formulate a principled optimization framework with discrete variable QCQP,  which provably prevents any inactive weights and enables the exact guarantee of meeting the resource constraints in terms of FLOPs and memory. Also, we extend the pruning granularity beyond channels and jointly prune individual 2D convolution filters spatially for greater efficiency. Our experiments show competitive pruning results under the target resource constraints on CIFAR-10 and ImageNet datasets on various network architectures.