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A Theoretical Analysis of Contrastive Unsupervised Representation Learning

Author(s): Saunshi, Nikunj; Plevrakis, Orestis; Arora, Sanjeev; Khodak, Mikhail; Khandeparkar, Hrishikesh

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Abstract: Recent empirical works have successfully used unlabeled data to learn feature representations that are broadly useful in downstream classification tasks. Several of these methods are reminiscent of the well-known word2vec embedding algorithm: leveraging availability of pairs of semantically “similar" data points and “negative samples," the learner forces the inner product of representations of similar pairs with each other to be higher on average than with negative samples. The current paper uses the term contrastive learning for such algorithms and presents a theoretical framework for analyzing them by introducing latent classes and hypothesizing that semantically similar points are sampled from the same latent class. This framework allows us to show provable guarantees on the performance of the learned representations on the average classification task that is comprised of a subset of the same set of latent classes. Our generalization bound also shows that learned representations can reduce (labeled) sample complexity on downstream tasks. We conduct controlled experiments in both the text and image domains to support the theory.
Publication Date: 2019
Citation: Saunshi, Nikunj, Orestis Plevrakis, Sanjeev Arora, Mikhail Khodak, and Hrishikesh Khandeparkar. "A Theoretical Analysis of Contrastive Unsupervised Representation Learning." In Proceedings of the 36th International Conference on Machine Learning (2019): pp. 5628-5637.
ISSN: 2640-3498
Pages: 5628 - 5637
Type of Material: Conference Article
Journal/Proceeding Title: Proceedings of the 36th International Conference on Machine Learning
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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