Variational Bayesian Inference is a popular methodology for approximating posterior distributions over Bayesian neural network weights. Recent work developing this class of methods has explored ever richer parameterizations of the approximate posterior in the hope of improving performance. In contrast, here we share a curious experimental finding that suggests instead restricting the variational distribution to a more compact parameterization. For a variety of deep Bayesian neural networks trained using Gaussian mean-field variational inference, we find that the posterior standard deviations consistently exhibit strong low-rank structure after convergence. This means that by decomposing these variational parameters into a low-rank factorization, we can make our variational approximation more compact without decreasing the models' performance. Furthermore, we find that such factorized parameterizations improve the signal-to-noise ratio of stochastic gradient estimates of the variational lower bound, resulting in faster convergence.

通过对高斯均值场变分推理方法训练的深层贝叶斯神经网络的后验标准差进行矩阵低秩分解，我们可以将变分推理方法更紧凑地参数化，并提高其信噪比，从而加速其收敛速度。

k-tied正态分布：贝叶斯神经网络中高斯均值场后验的紧凑参数化