A deep fully-connected neural network with an i.i.d. prior over its parameters is equivalent to a Gaussian process (GP) in the limit of infinite network width. This correspondence enables exact Bayesian inference for neural networks on regression tasks by means of straightforward matrix computations. For single hidden-layer networks, the covariance function of this GP has long been known. Recently, kernel functions for multi-layer random neural networks have been developed, but only outside of a Bayesian framework. As such, previous work has not identified the correspondence between using these kernels as the covariance function for a GP and performing fully Bayesian prediction with a deep neural network. In this work, we derive this correspondence and develop a computationally efficient pipeline to compute the covariance functions. We then use the resulting GP to perform Bayesian inference for deep neural networks on MNIST and CIFAR-10. We find that the GP-based predictions are competitive and can outperform neural networks trained with stochastic gradient descent. We observe that the trained neural network accuracy approaches that of the corresponding GP-based computation with increasing layer width, and that the GP uncertainty is strongly correlated with prediction error. We connect our observations to the recent development of signal propagation in random neural networks.

本文研究无限宽深层神经网络和高斯过程的等价性，提出一种计算高斯过程协方差函数的有效方法，并使用该方法在MNIST和CIFAR-10上进行了贝叶斯推断，在网络宽度增加时，训练神经网络的准确率和GP预测的不确定性分别增加，而有限宽度训练网络越接近GP，测试性能越好，GP预测通常优于有限宽度网络的预测，最后将这些GP的性能与随机神经网络的信号传播理论相联系。

深度神经网络作为高斯过程