Variational Autoencoder (VAE) is widely used as a generative model to approximate a model's posterior on latent variables by combining the amortized variational inference and deep neural networks. However, when paired with strong autoregressive decoders, VAE often converges to a degenerated local optimum known as "posterior collapse". Previous approaches consider the Kullback Leibler divergence (KL) individual for each datapoint. We propose to let the KL follow a distribution across the whole dataset, and analyze that it is sufficient to prevent posterior collapse by keeping the expectation of the KL's distribution positive. Then we propose Batch Normalized-VAE (BN-VAE), a simple but effective approach to set a lower bound of the expectation by regularizing the distribution of the approximate posterior's parameters. Without introducing any new model component or modifying the objective, our approach can avoid the posterior collapse effectively and efficiently. We further show that the proposed BN-VAE can be extended to conditional VAE (CVAE). Empirically, our approach surpasses strong autoregressive baselines on language modeling, text classification and dialogue generation, and rivals more complex approaches while keeping almost the same training time as VAE.

该研究论文提出 Batch Normalized-VAE (BN-VAE) 方法可以避免 Variational Autoencoder（VAE）寻找“后验塌缩”（posterior collapse）的局部最优解，该方法不需要引入新的模型组件或修改目标，可有效地、高效地避免后验塌缩，尤其在语言建模、文本分类和对话生成等任务上表现优异，且与 VAE 训练时间几乎相同。

批归一化推理网络防止 KL 消失