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Strong Implementation of Social Choice Functions in Dominant Strategies. Clemens Thielen Sven O. Krumke 3rd International Workshop on Computational Social Choice 15 September 2010 krumke@mathematik.uni-kl.de. TexPoint fonts used in EMF.
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Strong Implementation of Social Choice Functions in Dominant Strategies Clemens ThielenSven O. Krumke 3rd International Workshop on ComputationalSocial Choice 15 September 2010 krumke@mathematik.uni-kl.de TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAAAAAAAAAAA
Problem Definition • Social choice setting with private information: Strong Implementability
Mechanisms Mechanism: Types Bids Social Choices Agent 1 strategy α1 . . . g strategy αn Agent n . . . Strong Implementability
Utilities andEquilibria Definition: valuationoftheoutput paymentobtained Strong Implementability
Utilities andEquilibria Definition: Definition: Strong Implementability
Strong Implementation Definition: Strong Implementability
Strong Implementability Problem The Strong Implementability Problem: Encoding length: Strong Implementability
Augmented Revelation Mechanisms Definition: Augmented Revelation Principle: [Mookherjee, Reichelstein 1990] „incentivecompatibility“ Strong Implementability
PreviousResults Strong Implementability
Previous Results (2) Strong Implementability
OurResults Strong Implementability
Augmented Revelation Principle Augmented Revelation Principle: [Mookherjee, Reichelstein 1990] Augmented Revelation Principlefor Dominant Strategies: [thispaper] Strong Implementability
General Idea (I) • To obtain an augmented revelation mechanism: seedefinitiontofollowsoon Definition: Strong Implementability
Selective Elimination agenti Strong Implementability
Selective Elimination Strong Implementability
Bad Pairs and Elimination Definition: Definition: Definition: Strong Implementability
TwoImportantSteps Theorem 2 (selectiveeliminationisnecessary): Theorem 3 (selectiveeliminationissufficient): Strong Implementability
StructureoftheAlgorithm Theorem 3 + closelookattheproof guess Definitionofselectiveelimination guess verify Strong Implementability
The Verification General Approach: Main Observation: Strong Implementability
The Payment Polyhedron Strong Implementability
The Payment Polyhedron (I) Incentivecompatibility & dominant bids Inequalitiesencodewhichbidsare dominant bids. Strong Implementability
The Payment Polyhedron (II) Inequalitiesencodeconditionsofselectiveelimination Strong Implementability
The Payment Polyhedron (II) Inequalitiesencodeconditionsofselectiveelimination Strong Implementability
VerificationIssues Here I am! Strong Implementability
VerificationIssues Wehaveto handle strictinequalities. To do so, we must find a point in therelative interiorofthepolyhedron. Thiscanbedonebymeansofthe Ellipsoid Method (directly) orbysolving a sequenceof LPs. Byproduct: Paymentsareofpolynomialencodinglength. Strong Implementability
Conclusion NP-complete! • Strong Implementability in dominant strategiesÎNP • Characterizationresultgeneralizesto infinite type spaces • Open: Is theproblem in P? • Useful(?) results: • Augmented Revelation Principle • Selectiveeliminationprocedurewithpolynomiallymanysteps • Paymentsofpolynomialencodingsize Strong Implementability
Thank you! Strong Implementability