Unsupervised Deep Learning

Unsupervised learning looks set to play an ever more important role for deep neural networks, both as a way of harnessing vast quantities of unlabelled data, and as a means of learning representations that can rapidly generalise to new tasks and situations. The central challenge is how to determine what the objective function should be, when by definition we do not have an explicit target in mind. One approach, which this tutorial will cover in detail, is simply to ‘predict everything’ in the data, typically with a probabilistic model, which can be seen through the lens of the Minimum Description Length principle as an effort to compress the data as compactly as possible. However, we will also survey a range of other techniques, including un-normalized energy-based models, self-supervised algorithms and purely generative models such as GANs. Time allowing, we will extend our discussion to the reinforcement learning setting, where the natural analogue of unsupervised learning is intrinsic motivation, and notions such as curiosity, empowerment and compression progress are invoked as drivers of learning.