Structured Probabilistic Coding

This paper presents a new supervised representation learning framework, namely Structured Probabilistic Coding (SPC), to learn compact and informative representations from input related to the target task. SPC is an encoder-only probabilistic coding technology with a structured regularization from the target label space. By extracting compact and informative representations from input related to the target task, SPC can enhance the generalization ability of pre-trained language models for better language understanding. Specifically, the hidden representation is encoded into a Gaussian distribution space, while maximizing the prior entropy of latent representations concerning label space. This technique can simultaneously perform information encoding and task prediction in one module to more fully utilize the effective information from input data, and use variational inference in the output space to reduce randomness and uncertainty. To better control the probability distribution in the latent space, a structured regularization is proposed to promote class-level uniformity in the latent space. With the regularization term, SPC can preserve the Gaussian distribution structure of latent code as well as better cover the hidden space with class uniformly. We conduct evaluations on 12 natural language understanding tasks. The results show that our SPC can effectively improve the performance of pre-trained language models for various classification and regression tasks. Experiments demonstrate that SPC can enhance the generalization capability, robustness to label noise, and clustering quality of output representations.