Exploiting Unlabeled Data in CNNs by Self-Supervised Learning to Rank

Xialei Liu, Joost Van De Weijer, Andrew D. Bagdanov

    Research output: Contribution to journalArticleResearch

    69 Citations (Scopus)


    © 1979-2012 IEEE. For many applications the collection of labeled data is expensive laborious. Exploitation of unlabeled data during training is thus a long pursued objective of machine learning. Self-supervised learning addresses this by positing an auxiliary task (different, but related to the supervised task) for which data is abundantly available. In this paper, we show how ranking can be used as a proxy task for some regression problems. As another contribution, we propose an efficient backpropagation technique for Siamese networks which prevents the redundant computation introduced by the multi-branch network architecture. We apply our framework to two regression problems: Image Quality Assessment (IQA) and Crowd Counting. For both we show how to automatically generate ranked image sets from unlabeled data. Our results show that networks trained to regress to the ground truth targets for labeled data and to simultaneously learn to rank unlabeled data obtain significantly better, state-of-the-art results for both IQA and crowd counting. In addition, we show that measuring network uncertainty on the self-supervised proxy task is a good measure of informativeness of unlabeled data. This can be used to drive an algorithm for active learning and we show that this reduces labeling effort by up to 50 percent.
    Original languageEnglish
    Article number8642842
    Pages (from-to)1862-1878
    JournalIEEE Transactions on Pattern Analysis and Machine Intelligence
    Publication statusPublished - 1 Aug 2019


    • active learning
    • crowd counting
    • image quality assessment
    • Learning from rankings


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