Multiclass classification with bandit feedback using adaptive regularization

  • Authors:
  • Koby Crammer;Claudio Gentile

  • Affiliations:
  • Department of Electrical Engineering, The Technion, Haifa, Israel 32000;DICOM, Universita' dell'Insubria, Varese, Italy 21100

  • Venue:
  • Machine Learning
  • Year:
  • 2013

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Abstract

We present a new multiclass algorithm in the bandit framework, where after making a prediction, the learning algorithm receives only partial feedback, i.e., a single bit indicating whether the predicted label is correct or not, rather than the true label. Our algorithm is based on the second-order Perceptron, and uses upper-confidence bounds to trade-off exploration and exploitation, instead of random sampling as performed by most current algorithms. We analyze this algorithm in a partial adversarial setting, where instances are chosen adversarially, while the labels are chosen according to a linear probabilistic model which is also chosen adversarially. We show a regret of $\mathcal{O}(\sqrt{T}\log T)$ , which improves over the current best bounds of $\mathcal{O}(T^{2/3})$ in the fully adversarial setting. We evaluate our algorithm on nine real-world text classification problems and on four vowel recognition tasks, often obtaining state-of-the-art results, even compared with non-bandit online algorithms, especially when label noise is introduced.