Worst-Case Analysis of Selective Sampling for Linear-Threshold Algorithms

We provide a worst-case analysis of selective sampling algorithms for learning linear threshold functions. The algorithms considered in this paper are Perceptron-like algorithms, i. e. , algorithms which can be effi- ciently run in any reproducing kernel Hilbert space. Our algorithms ex- ploit a simple margin-based randomized rule to decide whether to query the current label. We obtain selective sampling algorithms achieving on average the same bounds as those proven for their deterministic coun- terparts, but using much fewer labels. We complement our theoretical findings with an empirical comparison on two text categorization tasks. The outcome of these experiments is largely predicted by our theoreti- cal results: Our selective sampling algorithms tend to perform as good as the algorithms receiving the true label after each classification, while observing in practice substantially fewer labels.

Authors

• Nicolò Cesa-Bianchi Universita degli Studi di Milano
• Claudio Gentile
• Luca Zaniboni

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