Compressing CNN by alternating constraint optimization framework

Abstract

Tensor decomposition has been extensively studied for convolutional neural networks (CNN) model compression. However, the direct decomposition of an uncompressed model into low-rank form causes unavoidable approximation error due to the lack of low-rank property of a pre-trained model. In this manuscript, a CNN model compression method using alternating constraint optimization framework (ACOF) is proposed. Firstly, ACOF formulates tensor decomposition-based model compression as a constraint optimization problem with low tensor rank constraints. This optimization problem is then solved systematically in an iterative manner using alternating direction method of multipliers (ADMM). During the alternating process, the uncompressed model gradually exhibits low-rank tensor property, and then the approximation error in low-rank tensor decomposition can be negligible. Finally, a high-performance CNN compression network can be effectively obtained by SGD-based fine-tuning. Extensive experimental results on image classification show that ACOF produces the optimal compressed model with high performance and low computational complexity. Notably, ACOF compresses Resnet56 to 28% without accuracy drop, and the compressed model have 1.14% higher accuracy than learning-compression (LC) method.