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Weian Li

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9 papers

1 author row

NeurIPS Conference 2025 Conference Paper

Beyond Last-Click: An Optimal Mechanism for Ad Attribution

Nan An
Weian Li
Qi Qi
Changyuan Yu
Liang Zhang

Accurate attribution for multiple platforms is critical for evaluating performance-based advertising. However, existing attribution methods rely heavily on the heuristic methods, e. g. , Last-Click Mechanism (LCM) which always allocates the attribution to the platform with the latest report, lacking theoretical guarantees for attribution accuracy. In this work, we propose a novel theoretical model for the advertising attribution problem, in which we aim to design the optimal dominant strategy incentive compatible (DSIC) mechanisms and evaluate their performance. We first show that LCM is not DSIC and performs poorly in terms of accuracy and fairness. To address this limitation, we introduce the Peer-Validated Mechanism (PVM), a DSIC mechanism in which a platform's attribution depends solely on the reports of other platforms. We then examine the accuracy of PVM across both homogeneous and heterogeneous settings, and provide provable accuracy bounds for each case. Notably, we show that PVM is the optimal DSIC mechanism in the homogeneous setting. Finally, numerical experiments are conducted to show that PVM consistently outperforms LCM in terms of attribution accuracy and fairness.

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I&C Journal 2025 Journal Article

Competition among parallel contests

Xiaotie Deng
Ningyuan Li
Weian Li
Qi Qi

We investigate the model of multiple rank-order contests held in parallel, where each contestant only selects one contest to join and each contest designer decides the prize structure to compete for the participation of contestants. We first analyze the strategic behaviors of contestants and completely characterize the symmetric Bayesian Nash equilibrium. As for the strategies of contest designers, when other designers' strategies are known, we show that computing the best response is NP-hard and propose a fully polynomial time approximation scheme to output the ϵ-approximate best response. When other designers' strategies are unknown, we provide a worst-case analysis on one designer's strategy. We give an upper bound on the worst-case utility of any strategy and propose a method to construct a strategy whose utility can guarantee a constant ratio of this upper bound in the worst case.

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TCS Journal 2025 Journal Article

Joint bidding in ad auctions

Yuchao Ma
Weian Li
Wanzhi Zhang
Yahui Lei
Zhicheng Zhang
Qi Qi
Qiang Liu
Xingxing Wang

In traditional advertising auctions, commodity suppliers as advertisers compete for adverting positions to display commodities. As e-commerce platforms become more prevalent, offline retailers are also opening online virtual shops, and retailers are starting to pay a fee for extra exposure of their shops. This has led to situations where a single commodity may be sponsored by both the retailer and the supplier, offering opportunities for more profit. In order to explore this novel advertising pattern, we propose a new model called the joint advertising system (JAS), where retailers and suppliers jointly bid for advertising positions. In the context of this realistic scenario, conventional mechanisms such as GFP, GSP and Myerson auction cannot be applied directly. Besides, the VCG mechanism results in negative revenue in JAS. To solve this issue, we modify the payment rule of VCG to create a revised VCG mechanism that guarantees incentive compatible, individually rational and weakly budget-balanced. Additionally, we leverage the structure of the affine maximizer auction (AMA) and the technique of automated mechanism design to train joint AMA. Finally, we conduct several experiments to demonstrate the performance of the joint AMA. It turns out that our mechanism maintains good economic properties and outperforms other mechanisms in various settings.

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TCS Journal 2025 Journal Article

Locating two facilities on a square with a minimum distance requirement

Weian Li
Yu Zhou

Classic works on facility location problems have been focused on the basic model where facilities and agents are distributed on one line. In this work, we study a new model where one facility or two facilities with a minimum distance requirement are to be located on a square (e. g. , a plaza) to serve the agents who are distributed on a line (e. g. , a street) that crosses the square. The actual positions of the agents are their private information, and our goal is to design strategyproof mechanisms that decide the locations to build the facilities such that the agents are incentivized to report their true positions and the social welfare is (approximately) maximized. We study different settings, where the facilities can be favorable or obnoxious and the distance metrics can be Manhattan or Euclidean. Interestingly, for Manhattan distances, all but one of our mechanisms achieve the optimal social welfare. For Euclidean distances, however, the optimal algorithms are not strategyproof. Accordingly, for each setting with Euclidean distances, we design strategyproof mechanisms that guarantee constant approximations of the optimal social welfare.

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AAAI Conference 2025 Conference Paper

Merging Mechanisms for Ads and Organic Items in E-commerce Platforms

Nan An
Weian Li
Qi Qi
Liang Zhang

In contemporary e-commerce platforms, search result pages display two types of items: ad items and organic items. Ad items are determined through an advertising auction system, while organic items are selected by a recommendation system. These systems have distinct optimization objectives, creating the challenge of effectively merging these two components. Recent research has explored merging mechanisms for e-commerce platforms, but none have simultaneously achieved all desirable properties: incentive compatibility, individual rationality, adaptability to multiple slots, integration of inseparable candidates, and avoidance of repeated exposure for ads and organic items. This paper addresses the design of a merging mechanism that satisfies all these properties. We first provide the necessary conditions for the optimal merging mechanisms. Next, we introduce two simple and effective mechanisms, termed the generalized fix mechanism and the generalized change mechanism. Finally, we theoretically prove that both mechanisms offer guaranteed approximation ratios compared to the optimal mechanism in both simplest and general settings.

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AAAI Conference 2025 Conference Paper

On Designing the Optimal Integrated Ad Auction in E-commerce Platforms

Yuchao Ma
Weian Li
Yuhan Wang
Zitian Guo
Yuejia Dou
Qi Qi
Changyuan Yu

Currently, e-commerce platforms integrate ads and organic content into a mixed list for users. While platforms seek to maximize profit from advertisers, organic items enhance user experience. To ensure long-term development, platforms aim to design mechanisms that optimize both revenue and user satisfaction. Current methods rank ads and organic items separately before integrating them. Even if each part is locally optimal, the combined result may not be globally optimal. In this paper, we come up with the Joint Integrated Regret Network (JINTER Net). Unlike traditional methods, which pre-order ads and organic items separately, JINTER Net directly selects from the combined set of candidate ads and organic items to generate an optimal list. This approach aims to optimally balance platform revenue and user experience while satisfying approximate dominant strategy incentive compatibility and individual rationality. We validate the effectiveness of JINTER Net using both synthetic data and real dataset, and our experimental results show that it significantly outperforms baseline models across multiple metrics.

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AAAI Conference 2024 Conference Paper

Competition among Pairwise Lottery Contests

Xiaotie Deng
Hangxin Gan
Ningyuan Li
Weian Li
Qi Qi

We investigate a two-stage competitive model involving multiple contests. In this model, each contest designer chooses two participants from a pool of candidate contestants and determines the biases. Contestants strategically distribute their efforts across various contests within their budget. We first show the existence of a pure strategy Nash equilibrium (PNE) for the contestants, and propose a fully polynomial-time approximation scheme to compute an approximate PNE. In the scenario where designers simultaneously decide the participants and biases, the subgame perfect equilibrium (SPE) may not exist. Nonetheless, when designers' decisions are made in two substages, the existence of SPE is established. In the scenario where designers can hold multiple contests, we show that the SPE always exists under mild conditions and can be computed efficiently.

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TCS Journal 2023 Journal Article

Optimally integrating ad auction into e-commerce platforms

Weian Li
Qi Qi
Changjun Wang
Changyuan Yu

Advertising becomes one of the most popular ways of monetizing an online transaction platform. Usually, sponsored advertisements are posted on the most attractive positions to enhance the number of clicks. However, multiple e-commerce platforms are aware that this action may hurt the search experience of users, even though it can bring more incomes. To balance the advertising revenue and the user experience loss caused by advertisements, most e-commerce platforms choose fixing some areas for advertisements and adopting some restrictions on the number of ads, such as a fixed number K of ads or one advertisement for every N organic searched results. Different from these common rules of treating the allocation of ads separately (from the arrangements of the organic searched items), in this work we build up an integrated system with mixed arrangements of advertisements and organic items. We focus on the design of truthful mechanisms to properly list the advertisements and organic items and optimally trade off the instant revenue and the user experience. Furthermore, for different settings and practical requirements, we extend our optimal truthful allocation mechanisms to cater for these realistic conditions. Finally, we exert several experiments to verify the improvement of our mechanism compared to the common-used advertising mechanism.

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TCS Journal 2017 Journal Article

Competitive profit maximization in social networks

Weian Li
Wenjing Liu
Tiantian Chen
Xiaoying Qu
Qizhi Fang
Ker-I Ko

We study the competitive profit maximization problem in a social network, which can be viewed as the profit maximization problem in a game-theoretic setting. We formulate two models called the profit maximization-agent (PM-A) game and the profit maximization-society (PM-S) game. By reducing them to be valid utility systems, we show that any Nash equilibrium provides an excepted social utility within a factor 1/2 (subject to a function-dependent additive term) of the optimum in the PM-A game and a factor of 1/2 of the optimum in the PM-S game. Furthermore, for the PM-S game, a polynomial-time algorithm is given for each player that can approximate the best response within a factor ( 1 − 1 / e ).

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