Representation learning seeks to expose certain aspects of observed data in a learned representation that's amenable to downstream tasks like classification. For instance, a good representation for 2D images might be one that describes only global structure and discards information about detailed texture. In this paper, we present a simple but principled method to learn such global representations by combining Variational Autoencoder (VAE) with neural autoregressive models such as RNN, MADE and PixelRNN/CNN. Our proposed VAE model allows us to have control over what the global latent code can learn and , by designing the architecture accordingly, we can force the global latent code to discard irrelevant information such as texture in 2D images, and hence the code only "autoencodes" data in a lossy fashion. In addition, by leveraging autoregressive models as both prior distribution $p(z)$ and decoding distribution $p(x|z)$, we can greatly improve generative modeling performance of VAEs, achieving new state-of-the-art results on MNIST, OMNIGLOT and Caltech-101 Silhouettes density estimation tasks.

本文提出了一种基于变分自编码器和神经自回归模型的简单但原则性的方法来学习全局表示，该方法允许对全局潜在特征进行控制，通过设计相应的架构，可以迫使全局潜在特征丢弃2D图像纹理等无关信息，并且通过利用自回归模型作为潜在分布和解码分布，可以大大提高VAE的生成建模性能，实现了MNIST、OMNIGLOT和Caltech-101 Silhouettes密度估计任务的新的最先进结果。

变分有损自编码器