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Contrastive Variational Autoencoder Enhances Salient Features

arXiv.org Machine Learning

Variational autoencoders are powerful algorithms for identifying dominant latent structure in a single dataset. In many applications, however, we are interested in modeling latent structure and variation that are enriched in a target dataset compared to some background---e.g. enriched in patients compared to the general population. Contrastive learning is a principled framework to capture such enriched variation between the target and background, but state-of-the-art contrastive methods are limited to linear models. In this paper, we introduce the contrastive variational autoencoder (cVAE), which combines the benefits of contrastive learning with the power of deep generative models. The cVAE is designed to identify and enhance salient latent features. The cVAE is trained on two related but unpaired datasets, one of which has minimal contribution from the salient latent features. The cVAE explicitly models latent features that are shared between the datasets, as well as those that are enriched in one dataset relative to the other, which allows the algorithm to isolate and enhance the salient latent features. The algorithm is straightforward to implement, has a similar run-time to the standard VAE, and is robust to noise and dataset purity. We conduct experiments across diverse types of data, including gene expression and facial images, showing that the cVAE effectively uncovers latent structure that is salient in a particular analysis.


Clustering by Directly Disentangling Latent Space

arXiv.org Machine Learning

To overcome the high dimensionality of data, learning latent feature representations for clustering has been widely studied recently. However, it is still challenging to learn "cluster-friendly" latent representations due to the unsupervised fashion of clustering. In this paper, we propose Disentangling Latent Space Clustering (DLS-Clustering), a new clustering mechanism that directly learning cluster assignment during the disentanglement of latent spacing without constructing the "cluster-friendly" latent representation and additional clustering methods. We achieve the bidirectional mapping by enforcing an inference network (i.e. encoder) and the generator of GAN to form a deterministic encoder-decoder pair with a maximum mean discrepancy (MMD)-based regularization. We utilize a weight-sharing procedure to disentangle latent space into the one-hot discrete latent variables and the continuous latent variables. The disentangling process is actually performing the clustering operation. Eventually the one-hot discrete latent variables can be directly expressed as clusters, and the continuous latent variables represent remaining unspecified factors. Experiments on six benchmark datasets of different types demonstrate that our method outperforms existing state-of-the-art methods. We further show that the latent representations from DLS-Clustering also maintain the ability to generate diverse and high-quality images, which can support more promising application scenarios.


Priors for Diversity in Generative Latent Variable Models

Neural Information Processing Systems

Probabilistic latent variable models are one of the cornerstones of machine learning. They offer a convenient and coherent way to specify prior distributions over unobserved structure in data, so that these unknown properties can be inferred via posterior inference. Such models are useful for exploratory analysis and visualization, for building density models of data, and for providing features that can be used for later discriminative tasks. A significant limitation of these models, however, is that draws from the prior are often highly redundant due to i.i.d. For example, there is no preference in the prior of a mixture model to make components non-overlapping, or in topic model to ensure that co-ocurring words only appear in a small number of topics.


Bayesian Reasoning with Deep-Learned Knowledge

arXiv.org Artificial Intelligence

We access the internalized understanding of trained, deep neural networks to perform Bayesian reasoning on complex tasks. Independently trained networks are arranged to jointly answer questions outside their original scope, which are formulated in terms of a Bayesian inference problem. We solve this approximately with variational inference, which provides uncertainty on the outcomes. We demonstrate how following tasks can be approached this way: Combining independently trained networks to sample from a conditional generator, solving riddles involving multiple constraints simultaneously, and combine deep-learned knowledge with conventional noisy measurements in the context of high-resolution images of human faces.


A Recurrent Latent Variable Model for Sequential Data

Neural Information Processing Systems

In this paper, we explore the inclusion of latent random variables into the hidden state of a recurrent neural network (RNN) by combining the elements of the variational autoencoder. We argue that through the use of high-level latent random variables, the variational RNN (VRNN) can model the kind of variability observed in highly structured sequential data such as natural speech. We empirically evaluate the proposed model against other related sequential models on four speech datasets and one handwriting dataset. Our results show the important roles that latent random variables can play in the RNN dynamics. Papers published at the Neural Information Processing Systems Conference.