Lea Learn rning ing to to Bi Bid d Wi With thout
- ut
Kn Knowin wing g yo your ur Va Valu lue
Zhe Feng, Harvard Joint work with Chara Podimata (Harvard) and Vasilis Syrgkanis (MSR)
19th ACM Conference on Economics and Computation, EC’18 6/21/2018 1
Lea Learn rning ing to to Bi Bid d Wi With thout out Kn - - PowerPoint PPT Presentation
Lea Learn rning ing to to Bi Bid d Wi With thout out Kn Knowin wing g yo your ur Va Valu lue Zhe Feng, Harvard Joint work with Chara Podimata (Harvard) and Vasilis Syrgkanis (MSR) 19th ACM Conference on Economics and Computation,
Zhe Feng, Harvard Joint work with Chara Podimata (Harvard) and Vasilis Syrgkanis (MSR)
19th ACM Conference on Economics and Computation, EC’18 6/21/2018 1
19th ACM Conference on Economics and Computation, EC’18 6/21/2018
Auction theory & Mechanism Design
Auction
Utility to buyer i: ui = aivi − pi
2
Key assumption in Auction Theory & Mechanism Design Private valuation but known to the bidder himself/herself
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Key assumption in Auction Theory & Mechanism Design Private valuation but known to the bidder himself/herself
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Key assumption in Auction Theory & Mechanism Design
Small markets; Bidders have time to prepare to bid (market research) Digital economy: online advertisement auctions; No time to prepare to bid (market research)
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Advertiser (Learner) bids Platform (Auctioneer)
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Advertiser (Learner) bids Platform (Auctioneer) Generates 𝑦𝑢(⋅), 𝑞𝑢(⋅)
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Advertiser (Learner) bids Platform (Auctioneer) Generates 𝑦𝑢(⋅), 𝑞𝑢(⋅) Clicked by users Generates value 𝑤𝑢
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Advertiser (Learner) bids Platform (Auctioneer) Generates 𝑦𝑢(⋅), 𝑞𝑢(⋅) Clicked by users Generates value 𝑤𝑢 Observes (estimated) 𝑦𝑢(⋅), 𝑞𝑢(⋅)
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Advertiser (Learner) bids Platform (Auctioneer) Generates 𝑦𝑢(⋅), 𝑞𝑢(⋅) Observes (estimated) 𝑦𝑢(⋅), 𝑞𝑢(⋅)
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Advertiser (Learner) bids Platform (Auctioneer) Generates 𝑦𝑢(⋅), 𝑞𝑢(⋅) Clicked by users Generates value 𝑤𝑢 Expected utility 𝑣𝑢(𝑐) = (𝑤𝑢−𝑞𝑢 𝑐 ) ⋅ 𝑦𝑢(𝑐) Reward 𝑤𝑢 − 𝑞𝑢(⋅) Observes (estimated) 𝑦𝑢(⋅), 𝑞𝑢(⋅)
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⋅ 𝒚𝒖(𝒄)
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⋅ 𝒚𝒖(𝒄)
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𝑺 𝑼 = 𝐭𝐯𝐪
𝒄∗ 𝔽 𝒖=𝟐 𝑼
𝒗𝒖(𝒄∗) − 𝔽
𝒖=𝟐 𝑼
𝒗𝒖(𝒄𝒖)
Utility with best fixed bid in hindsight Utility with bids generated by algorithm
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Utilize partial feedback information from the auctions. Partial feedback: between bandit feedback and full information feedback Recall: EXP3 achieves 𝑷( 𝑼|𝑪|)
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From auctioneer side: [Blum et. al, 04], [Amin et. al, 05], [Amin et. al, 06], [Cesa-Bianchi et.al, 15], … From bidder side: [Dikkala & Tardos, 13], [Balseiro & Gur, 17], [Weed et. al, 16]
Contextual Bandit: [Bubeck & Cesa-Bianchi, 12] [Agarwal et. al, 14]… Feedback graphs: [Alon et. al, 13], [Alon et. al, 15]
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and allocation function 𝒚𝒖(⋅).
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and allocation function 𝒚𝒖(⋅).
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and allocation function 𝒚𝒖(⋅).
also learns 𝒔𝒖(⋅)
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𝒗𝒖 𝒄 = (𝒔𝒖 𝒄 −𝟐) ⋅ 𝒚𝒖 (𝒄) σ𝒄 𝝆𝒖 𝒄 𝒚𝒖(𝒄) , 𝐣𝐠 𝐮𝐢𝐟 𝐦𝐟𝐛𝐬𝐨𝐟𝐬 𝐱𝐣𝐨𝐭 − 𝟐 − 𝒚𝒖 𝒄 𝟐 − σ𝒄 𝝆𝒖 𝒄 𝒚𝒖 𝒄 , 𝐣𝐠 𝐮𝐢𝐟 𝐦𝐟𝐛𝐬𝐨𝐟𝐬 𝐞𝐩𝐟𝐭𝐨′𝐮 𝐱𝐣𝐨
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𝒗𝒖 𝒄 = (𝒔𝒖 𝒄 −𝟐) ⋅ 𝒚𝒖 (𝒄) σ𝒄 𝝆𝒖 𝒄 𝒚𝒖(𝒄) , 𝐣𝐠 𝐮𝐢𝐟 𝐦𝐟𝐛𝐬𝐨𝐟𝐬 𝐱𝐣𝐨𝐭 − 𝟐 − 𝒚𝒖 𝒄 𝟐 − σ𝒄 𝝆𝒖 𝒄 𝒚𝒖 𝒄 , 𝐣𝐠 𝐮𝐢𝐟 𝐦𝐟𝐛𝐬𝐨𝐟𝐬 𝐞𝐩𝐟𝐭𝐨′𝐮 𝐱𝐣𝐨
𝒗𝒖 𝒄 )
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2. 𝒗𝒖(𝒄) is the unbiased estimator of 𝒗𝒖 𝒄 − 𝟐 [Lemma 1] 𝑺 𝑼 ≤
𝜽 𝟑 σ𝒖=𝟐 𝑼
σ𝒄∈𝑪 𝝆𝒖 𝒄 ⋅ 𝔽 ෦ 𝒗𝒖 𝒄 𝟑 +
𝟐 𝜽 𝒎𝒑𝒉(|𝑪|)
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2. 𝒗𝒖(𝒄) is the unbiased estimator of 𝒗𝒖 𝒄 − 𝟐 [Lemma 1] 𝑺 𝑼 ≤
𝜽 𝟑 σ𝒖=𝟐 𝑼
σ𝒄∈𝑪 𝝆𝒖 𝒄 ⋅ 𝔽 ෦ 𝒗𝒖 𝒄 𝟑 +
𝟐 𝜽 𝒎𝒑𝒉(|𝑪|)
𝒄∈𝑪
𝝆𝒖 𝒄 ⋅ 𝔽 ෦ 𝒗𝒖 𝒄 𝟑 ≤ 𝟔 (𝟐) Q.E.D Note: in EXP3, (1) grows as # of actions.
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Beyond Binary outcomes: a set of outcomes 𝑷
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Beyond Binary outcomes: a set of outcomes 𝑷
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Beyond Binary outcomes: a set of outcomes 𝑷
𝒔𝒖(𝒄𝒖, 𝒑𝒖).
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Beyond Binary outcomes: a set of outcomes 𝑷
𝒔𝒖(𝒄𝒖, 𝒑𝒖).
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Beyond Binary outcomes: a set of outcomes 𝑷
𝒔𝒖(𝒄𝒖, 𝒑𝒖).
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appropriately
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appropriately
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appropriately
getting item
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Piecewise-Lipschitz rewards
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Theorem 3 (Regret of WIN-EXP algorithm in the continuous action space with 𝚬𝒑-Piecewise 𝑴-Lipschitz Average Utilities). WIN-EXP algorithm achieves regret at most 2 𝟑𝒆𝑼|𝑷|𝐦𝐩𝐡(𝐧𝐛𝐲{
𝟐 𝚬𝐩 , 𝑴𝑼})+1
Δ𝑝: length of minimum interval
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iterations 𝒖 and 𝒖′
iterations 𝒖 and 𝒖′
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𝝇𝒍+𝟐 𝒕𝒍 , where 𝝇𝒍+𝟐 is the score-weighted
bid of bidder wins slot 𝒍 + 𝟐
Lipschitz CDF
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Set up:
Weighted GSP auctions; 𝒘𝒋 ∈ 𝟏, 𝟐 , randomly draw 20 bidders, 3 slots Consider three behaviors for other bidders (opponents): Stochastic, EXP3, WIN-EXP
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Different discretization of bidding space
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Robust to Noisy CTR Estimates: 𝑶 𝟏,
𝟐 𝒏
Stochastic adversaries
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Robust to Noisy CTR Estimates: 𝑶 𝟏,
𝟐 𝒏
EXP3 adversaries
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Robust to Noisy CTR Estimates: 𝑶 𝟏,
𝟐 𝒏
WIN-EXP adversaries
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Robust to CTR/payment estimates w/ regression
the repeated auctions without knowing your value
MAB algorithm
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