- Tianshui Chen, Liang Lin, Wangmeng Zuo, Xiaonan Luo, Lei Zhang, “Learning a Wavelet-like Auto-Encoder to Accelerate Deep Neural Networks”, Association for the Advancement of Artificial Intelligence (AAAI), 2018. (oral presentation) Paper Code
Accelerating deep neural networks (DNNs) has been attracting increasing attention as it can benefit a wide range of applications, e.g., enabling mobile systems with limited computing resources to own powerful visual recognition ability. A practical strategy to this goal usually relies on a two stage process: operating on the trained DNNs (e.g., approximating the convolutional filters with tensor decomposition) and finetuning the amended network, leading to difficulty in balancing the trade-off between acceleration and maintaining recognition performance. In this work, aiming at a general and comprehensive way for neural network acceleration, we develop a Wavelet-like Auto-Encoder (WAE) that decomposes the original input image into two low-resolution channels (sub-images) and incorporate the WAE into the classification neural networks for joint training. The two decomposed channels, in particular, are encoded to carry the low-frequency information (e.g., image profiles) and high-frequency (e.g., image details or noises), respectively, and enable reconstructing the original input image through the decoding process. Then, we feed the low-frequency channel into a standard classification network such as VGG or ResNet and employ a very lightweight network to fuse with the high-frequency channel to obtain the classification result. Compared to existing DNN acceleration solutions, our framework has the following advantages: i) it is tolerant to any existing convolutional neural networks for classification without amending their structures; ii) the WAE provides an interpretable way to preserve the main components of the input image for classification.
Figure: The overall framework of our proposed method. The key component of the framework is the WAE that decomposes an input image into two low-resolution channels, i.e., IL and IH. These two channels encode the high- and low-frequency information respectively and are enabled to construct the original image via a decoding process. The low-frequency channel is then fed into the a standard network (e.g., VGG16-Net or ResNet) to extract its features. Then a lightweight network fuses these features and the high-frequency channel to predict the label scores. Note that the input to the classification network is low-resolution; thus it enjoys higher efficiency.
WAE Network Architecture
Figure: Detailed architecture of the wavelet-like autoencoder. It consists of an encoding (the blue part) and a decoding (the green part) layers. “/2” denotes a conv layer with a stride of 2 to downsample the feature maps, and conversely “×2” denotes a deconv layer with a stride of 2 to upsample the feature maps.
Table: Comparison of the top-5 error rate, execution time and speed-up rate on CPU and GPU of VGG16-Net, the two baseline methods and the previous state of the art methods on the ImageNet dataset. The error rate is measured on single-view without data augmentation.
Table: Comparison of the top-5 error rate and speed-up rate (SR) of our model and ThiNet on ResNet-50 on the ImageNet dataset.
 Karen Simonyan, Andrew Zisserman, Very Deep Convolutional Networks for Large-Scale Image Recognition, ICLR 2015.
 Kaiming He, Xiangyu Zhang, Shaoqing Ren, Jian Sun, Deep Residual Learning for Image Recognition, CVPR 2016.
 Jian-Hao Luo, Jianxin Wu, and Weiyao Lin. Thinet: A filter level pruning method for deep neural network compression, arXiv preprint arXiv:1707.06342.
 Pavlo Molchanov, Stephen Tyree, Tero Karras, Timo Aila, Jan Kautz, Pruning Convolutional Neural Networks for Resource Efficient Inference, arXiv preprint arXiv:1611.06440.