  This paper aims to accelerate the test-time computation of convolutional
neural networks (CNNs), especially very deep CNNs that have substantially
impacted the computer vision community. Unlike previous methods that are
designed for approximating linear filters or linear responses, our method takes
the nonlinear units into account. We develop an effective solution to the
resulting nonlinear optimization problem without the need of stochastic
gradient descent (SGD). More importantly, while previous methods mainly focus
on optimizing one or two layers, our nonlinear method enables an asymmetric
reconstruction that reduces the rapidly accumulated error when multiple (e.g.,
>=10) layers are approximated. For the widely used very deep VGG-16 model, our
method achieves a whole-model speedup of 4x with merely a 0.3% increase of
top-5 error in ImageNet classification. Our 4x accelerated VGG-16 model also
shows a graceful accuracy degradation for object detection when plugged into
the Fast R-CNN detector.
