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Efficient Regret Bounds for Online Bid Optimisation in Budget-Limited Sponsored Search Auctions
Proceedings of the 30th Conference on Uncertainty in Artificial Intelligence, PMLR R12:479-488, 2014.
Abstract
We study the problem of an advertising agent who needs to intelligently distribute her bud- get across a sequence of online keyword bid- ding auctions. We assume the closing price of each auction is governed by the same un- known distribution, and study the problem of making provably optimal bidding deci- sions. Learning the distribution is done un- der censored observations, i.e. the closing price of an auction is revealed only if the bid we place is above it. We consider three al- gorithms, namely $\varepsilon$-First, Greedy Product- Limit (GPL) and LuekerLearn, respectively, and we show that these algorithms provably achieve Hannan-consistency. In particular, we show that the regret bound of $\varepsilon$-First is at most O(T 2 3 ) with high probability. For the other two algorithms, we first prove that, by using a censored data distribution esti- mator proposed by Zeng [19], the empirical distribution of the closing market price con- verges in probability to its true distribution with a O( 1 $\sqrt{}$ t) rate, where t is the number of updates. Based on this result, we prove that both GPL and LuekerLearn achieve O( $\sqrt{}$ T) regret bound with high probability. This in fact provides an affirmative answer to the re- search question raised in [1]. We also evalu- ate the abovementioned algorithms using real bidding data, and show that although GPL achieves the best performance on average (up to 90% of the optimal solution), its long run- ning time may limit its suitability in practice. By contrast, LuekerLearn and $\varepsilon$-First pro- posed in this paper achieve up to 85% of the optimal, but with an exponential reduction in computational complexity (a saving up to 95%, compared to GPL).