Bid-aware Gradient Descent for Unbiased Learning with Censored Data in Display Advertising
Weinan Zhang*, University College London; Tianxiong Zhou, TukMob; Jun Wang, University College London; Jian Xu, TouchPal Inc
In real-time display advertising, ad slots are sold per impression via an auction mechanism. For an advertiser, the campaign information is incomplete — the user responses (e.g, clicks or conversions) and the market price of each ad impression are observed only if the advertiser’s bid had won the corresponding ad auction. The predictions, such as bid land-scape forecasting, click-through rate (CTR) estimation, and bid optimization, are all operated in the pre-bid stage with full-volume bid request data. However, the training data is gathered in the post-bid stage with a strong bias towards the winning impressions. A common solution for learning over such censored data is to reweight data instances to correct the discrepancy between training and prediction. However, little study has been done on how to obtain the weights in-dependent of previous bidding strategies and consequently integrate them into the ﬁnal CTR prediction and bid generation steps. In this paper, we formulate CTR estimation and bid optimization under such censored auction data. Derived from a survival model, we show that historic bid information is naturally incorporated to produce Bid-aware Gradient De-scents (BGD) which controls both the importance and the direction of the gradient to achieve unbiased learning. The empirical study based on two large-scale real-world datasets demonstrates remarkable performance gains from our solution. The learning framework has been deployed on Yahoo!’s real-time bidding platform and provided 2.97% AUC lift for CTR estimation and 9.30% eCPC drop for bid optimization in an online A/B test.
Filed under: Classification