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This paper explores the concept of Strong Implementability in the context of social choice functions with private information, focusing on mechanisms and utilities. It discusses the Strong Implementability Problem, Augmented Revelation Mechanisms, Selective Elimination, and the Payment Polyhedron in detail. The study provides insights into the complexities of verification and establishes the NP-completeness of the Strong Implementability problem. The research also presents useful results such as the Augmented Revelation Principle and procedures with polynomially many steps. Thank you for reading!
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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