  Second-order information has proven to be very effective in determining the
redundancy of neural network weights and activations. Recent paper proposes to
use Hessian traces of weights and activations for mixed-precision quantization
and achieves state-of-the-art results. However, prior works only focus on
selecting bits for each layer while the redundancy of different channels within
a layer also differ a lot. This is mainly because the complexity of determining
bits for each channel is too high for original methods. Here, we introduce
Channel-wise Hessian Aware trace-Weighted Quantization (CW-HAWQ). CW-HAWQ uses
Hessian trace to determine the relative sensitivity order of different channels
of activations and weights. What's more, CW-HAWQ proposes to use deep
Reinforcement learning (DRL) Deep Deterministic Policy Gradient (DDPG)-based
agent to find the optimal ratios of different quantization bits and assign bits
to channels according to the Hessian trace order. The number of states in
CW-HAWQ is much smaller compared with traditional AutoML based mix-precision
methods since we only need to search ratios for the quantization bits. Compare
CW-HAWQ with state-of-the-art shows that we can achieve better results for
multiple networks.
