Scheduling Without Payments

  • Authors:
  • Elias Koutsoupias

  • Affiliations:
  • Department of Computer Science, University of Oxford, Oxford, UK OX1 3QD and Department of Informatics and Telecommunications, University of Athens, Athens, Greece 15784

  • Venue:
  • Theory of Computing Systems
  • Year:
  • 2014

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Abstract

We consider mechanisms without payments for the problem of scheduling unrelated machines. Specifically, we consider truthful in expectation randomized mechanisms under the assumption that a machine (player) is bound by its reports: when a machine lies and reports value $\tilde{t}_{ij}$ for a task instead of the actual one tij, it will execute for time $\tilde{t}_{ij}$ if it gets the task (unless the declared value $\tilde{t}_{ij}$ is less than the actual value tij, in which case, it will execute for time tij). Our main technical result is an optimal mechanism for one task and n players which has approximation ratio (n+1)/2. We also provide a matching lower bound, showing that no other truthful mechanism can achieve a better approximation ratio. This immediately gives an approximation ratio of (n+1)/2 and n(n+1)/2 for social cost and makespan minimization, respectively, for any number of tasks. We also study the price of anarchy of natural algorithms.