Variational autoencoders employ an amortized inference model to approximate the posterior of latent variables. However, such amortized variational inference faces two challenges: (1) the limited posterior expressiveness of fully-factorized Gaussian assumption and (2) the amortization error of the inference model. We present a novel approach that addresses both challenges. First, we focus on ReLU networks with Gaussian output and illustrate their connection to probabilistic PCA. Building on this observation, we derive an iterative algorithm that finds the mode of the posterior and apply full-covariance Gaussian posterior approximation centered on the mode. Subsequently, we present a general framework named Variational Laplace Autoencoders (VLAEs) for training deep generative models. Based on the Laplace approximation of the latent variable posterior, VLAEs enhance the expressiveness of the posterior while reducing the amortization error. Empirical results on MNIST, Omniglot, Fashion-MNIST, SVHN and CIFAR10 show that the proposed approach significantly outperforms other recent amortized or iterative methods on the ReLU networks.

该研究提出了一种名为“变分Laplace自动编码器”的深度生成模型的一般框架，在近似后验分布时采用拉普拉斯近似方法，提高后验表现，同时减少摊销误差。在MNIST，Omniglot，Fashion-MNIST，SVHN和CIFAR10数据集上进行的实验证明，该方法显着优于ReLU网络上其他最近的摊销或迭代方法。

变分Laplace自编码器