Pushing the Envelope: new research topics at the interface of cs and econ/gt

1. Pushing the Envelope:new research topics at the interface of cs and econ/gt Yoav Shoham Stanford University (many debts are due)

2. Primary areas of interaction so far • Computing solution concepts, primarily NE • Multi-agent learning • Compact games (graphical games, MAIDs, game networks, local-effect games, social networks, …) • Mechanism design, in particular auctions BAGT Symposium

3. Talk Outline • Computing solution concepts, primarily NE • The role of NE unclear • Multi-agent learning • Ditto • Compact games (graphical games, MAIDs, game networks, local-effect games, social networks, …) • Other forms of compactness, and what about coalitional games? • Mechanism design, in particular auctions • Behavioral Mechanism design • Beyond GT: Algorithmic Institutional Design BAGT Symposium

4. A game with a trivial, unique NE Matching Pennies Rochambeau (Rock-Paper-Scissors) BAGT Symposium

5. A game with a trivial, unique NE Matching Pennies Rochambeau (Rock-Paper-Scissors) (www.worldrps.com) BAGT Symposium

6. A game with a trivial, unique NE Matching Pennies Rochambeau (Rock-Paper-Scissors) (www.worldrps.com) Lesson: Nash equilibrium not necessarily instructive BAGT Symposium

7. Some Intuition about Learning Stackelberg Game BAGT Symposium

8. Some Intuition about Learning Stackelberg Game Lesson: can’t separate learning from teaching BAGT Symposium

9. Five Distinct Research Agendas in MAL • Computation: Quick-and-dirty method for (e.g.) NE • Social science: How people (institutions, animals…) learn. • Game theory puritanism: Equilibria of learning strategies. • Distributed control: Learning in common-payoff games. • Targeted learning: Learning when you have some sense of how your opponents might behave. BAGT Symposium

10. Lesson: Need to take NE with a grain of salt • Beautiful, clever • Makes it hard to back off from assumptions of perfect rationality; can we have an alternative, “constructive” game theory? • In any event, “best response” computation merits as much attention as eqm BAGT Symposium

11. Talk Outline • Computing solution concepts, primarily NE • The role of NE unclear • Multi-agent learning • Ditto • Compact games (graphical games, MAIDs, game networks, local-effect games, social networks, …) • Other forms of compactness, and what about coalitional games? • Mechanism design, in particular auctions • Behavioral Mechanism design • Beyond GT: Algorithmic Institutional Design BAGT Symposium

12. On compact representations • Compact representations are fine; need more • Programming constructs in strategy descriptions (“programmatic rationality”) • Partial games (e.g., logic-based game description) • What about coalitional games? BAGT Symposium

13. Marginal Contribution Nets • Games represented by sets of rules pattern  value { a & b & c } 5 • Value of a group S equals the sum of the values of the rules Ssatisfies v(S) = {r : S satisfies r}v(r) • Focus on conjunction & negation in pattern BAGT Symposium

14. Conciseness of MC-Nets Theorem MC-Nets generalize the multi-issue representation of [CS04] Theorem MC-Nets generalize the graphical representation of [DP94] BAGT Symposium

15. Computational Leverage • Shapley value can be efficiently computed in MC-nets • Exploiting Additivity and Symmetry • Determining membership in core is hard, but one can determine membership in time exponential in treewidth • Determining emptiness, or finding an arbitrary member of a non-empty core, are no harder BAGT Symposium

16. Talk Outline • Computing solution concepts, primarily NE • The role of NE unclear • Multi-agent learning • Ditto • Compact games (graphical games, MAIDs, game networks, local-effect games, social networks, …) • Other forms of compactness, and what about coalitional games? • Mechanism design, in particular auctions • Behavioral Mechanism design • Beyond GT: Algorithmic Institutional Design BAGT Symposium

17. Recall some results from auction theory • Informal observations • Dutch = First-price, sealed bid • English  Second-price, sealed bid (cf. proxy bidding) • Japanese ≠ English • Second-price and Japanese have dominant strategies • For precise analyses, need to distinguish between • Common values and independent values (winner’s curse) • Risk averse, risk-neutral and risk-seeking bidders • Formal results speak to: • Whether an auction is “incentive compatible” • Whether the auction is “efficient” • Whether the auction is “revenue maximizing” BAGT Symposium

18. Example of BMD: Online marketing • The X5 story • What are we optimizing for? • Behavioral requirements (BMD) (ack: Moshe Tennenholtz) • # sign-ups • # return visits (magic number: 5) • Message injection • Product education • Truthful consumer surveys • Yields a new perspective on existing mechanisms • Suggests new mechanisms BAGT Symposium

19. Some new truths about auctions, from the perspective of marketing • First-price sealed-bid auction ≠ Dutch auction • Second-price sealed-bid auction ≠ English auction • Dominant-strategy mechanisms can be suboptimal • Barter- and multiple-currency markets might trump markets with universal currency BAGT Symposium

20. Some new, marketing-oriented mechanisms • Tournament auction • Infinitely many equilibria • Average-price auction • Giving the little guy a chance • Team bidding • Cooperation • Community auction • Coopetition • Online collectibles • The marketing advantages of barter systems • Preference auction • Win-win for the auctioneer and buyers BAGT Symposium

21. Tournament auction A series of sealed-bid auctions; X% make it to the next day; person with highest remaining points wins. BAGT Symposium

22. Tournament auction Other activities added to basic tournament auction BAGT Symposium

23. Inserting a population game into an auction Capturing information about consumers and their views of others; the latter is particularly truthful. BAGT Symposium

24. Average Price Game The consumer who bids closest to the average of all bids wins the prize. BAGT Symposium

25. Team Bidding Bidders form teams and pool their bids. BAGT Symposium

26. Community Auction … Cariocas’ Community Auction A “global bid” triggers the close of multiple auctions. BAGT Symposium

27. Online collectibles Online collection of digital objects, initially assembled by various online activities. BAGT Symposium

28. Online collectibles … and then exchanged via online barter BAGT Symposium

29. Main takeaways • Marketing considerations completely change the rules of the game. Some lessons of BMD: • new design criteria • new perspectives on existing mechanisms • new mechanisms • Many applications beyond marketing. Example: Captchas, ESP • A lot more work is needed before this becomes a science BAGT Symposium

30. Talk Outline • Computing solution concepts, primarily NE • The role of NE unclear • Multi-agent learning • Ditto • Compact games (graphical games, MAIDs, game networks, local-effect games, social networks, …) • Other forms of compactness, and what about coalitional games? • Mechanism design, in particular auctions • Behavioral Mechanism design • Beyond GT: Algorithmic Institutional Design BAGT Symposium

31. Algorithmic Institutional Design (ack: Mike Munie) • What is better: The EE or CS qual structure at Stanford? • Similar for job interviews, admissions, consumer surveys, etc • Reminiscent of, but distinct from, the “secretary problem” • The answer: Depends on what you’re optimizing for. And even given that, depends. BAGT Symposium

32. Formal Model, continued BAGT Symposium

33. Results • Multiple versions • Single prof? • Single student? • Parallel or sequential? • Sample results • Even in simplest case, selecting an optimal set of questions is NP-Hard, and is not submodular, so there is a not an obvious approximation algorithm • Sequentiality can be maximally helpful • In the multiagent setting, even deciding between committee structures is NP-Hard • *Seems* like there are well behaved special cases BAGT Symposium

34. Talk Outline • Computing solution concepts, primarily NE • The role of NE unclear • Multi-agent learning • Ditto • Compact games (graphical games, MAIDs, game networks, local-effect games, social networks, …) • Other forms of compactness, and what about coalitional games? • Mechanism design, in particular auctions • Behavioral Mechanism design • Beyond GT: Algorithmic Institutional Design BAGT Symposium

35. thank you! BAGT Symposium