Title: A Gradient-based Kernel Approach for Efficient Network Architecture Search. Abstract: It is widely accepted  that vanishing and exploding gradient values are the main reason behind the difficulty of deep network training.
In this work, we take a further step to understand the optimization of deep networks and find that both gradient correlations and gradient values have strong impacts on model training. 
Inspired by our new finding, we explore a simple yet effective network architecture search (NAS) approach that leverages gradient correlation and gradient values to find well-performing architectures. To be specific, we first  formulate these two terms into a unified gradient-based kernel and then select architectures with the largest kernels at initialization as the final networks. 
The new approach replaces the expensive  ``train-then-test'' evaluation paradigm  with a new lightweight function according to the gradient-based kernel at initialization.
Experiments show that our approach achieves competitive results with orders of magnitude faster than ``train-then-test'' paradigms on image classification tasks. Furthermore, the extremely low search cost enables its wide applications. It also obtains performance improvements on two text classification tasks.