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McRank: Learning to Rank Using Multiple Classification and Gradient Boosting
Ping Li · Chris J Burges · Qiang Wu

Tue Dec 04 03:20 PM -- 03:30 PM (PST) @ None

We cast the ranking problem as (1) multiple classification (``Mc'') (2) multiple ordinal classification, which lead to computationally tractable learning algorithms for relevance ranking in Web search. We consider the DCG criterion (discounted cumulative gain), a standard quality measure in information retrieval. Our approach is motivated by the fact that perfect classifications result in perfect DCG scores and the DCG errors are bounded by classification errors. We propose using the {\em Expected Relevance} to convert class probabilities into ranking scores. The class probabilities are learned using a gradient boosting tree algorithm. Evaluations on large-scale datasets show that our approach can improve {\em LambdaRank}\cite{Proc:BurgesNIPS06} and the regressions-based ranker\cite{Proc:ZhangCOLT06}, in terms of the (normalized) DCG scores. An efficient implementation of the boosting tree algorithm is also presented.

Author Information

Ping Li (Baidu Research USA)
Chris J Burges (Microsoft Research)
Qiang Wu (Department of Computer Science and Engineering)

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