Bidding mechanisms in graph games

Guy Avni, Thomas A. Henzinger, Ðorđe Žikelić

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


In two-player games on graphs, the players move a token through a graph to produce a finite or infinite path, which determines the qualitative winner or quantitative payoff of the game. We study bidding games in which the players bid for the right to move the token. Several bidding rules were studied previously. In Richman bidding, in each round, the players simultaneously submit bids, and the higher bidder moves the token and pays the other player. Poorman bidding is similar except that the winner of the bidding pays the “bank” rather than the other player. Taxman bidding spans the spectrum between Richman and poorman bidding. They are parameterized by a constant τ ∈ [0, 1]: portion τ of the winning bid is paid to the other player, and portion 1 − τ to the bank. While finite-duration (reachability) taxman games have been studied before, we present, for the first time, results on infinite-duration taxman games. It was previously shown that both Richman and poorman infinite-duration games with qualitative objectives reduce to reachability games, and we show a similar result here. Our most interesting results concern quantitative taxman games, namely mean-payoff games, where poorman and Richman bidding differ significantly. A central quantity in these games is the ratio between the two players’ initial budgets. While in poorman mean-payoff games, the optimal payoff of a player depends on the initial ratio, in Richman bidding, the payoff depends only on the structure of the game. In both games the optimal payoffs can be found using (different) probabilistic connections with random-turn games in which in each turn, instead of bidding, a coin is tossed to determine which player moves. While the value with Richman bidding equals the value of a random-turn game with an un-biased coin, with poorman bidding, the bias in the coin is the initial ratio of the budgets. We give a complete classification of mean-payoff taxman games that is based on a probabilistic connection: the value of a taxman bidding game with parameter τ and initial ratio r, equals the value of a random-turn game that uses a coin with bias (Formula presented.). Thus, we show that Richman bidding is the exception; namely, for every τ < 1, the value of the game depends on the initial ratio. Our proof technique simplifies and unifies the previous proof techniques for both Richman and poorman bidding.

Original languageEnglish
Title of host publication44th International Symposium on Mathematical Foundations of Computer Science, MFCS 2019
EditorsJoost-Pieter Katoen, Pinar Heggernes, Peter Rossmanith
PublisherSchloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing
ISBN (Electronic)9783959771177
StatePublished - Aug 2019
Externally publishedYes
Event44th International Symposium on Mathematical Foundations of Computer Science, MFCS 2019 - Aachen, Germany
Duration: 26 Aug 201930 Aug 2019

Publication series

NameLeibniz International Proceedings in Informatics, LIPIcs
ISSN (Print)1868-8969


Conference44th International Symposium on Mathematical Foundations of Computer Science, MFCS 2019

Bibliographical note

Publisher Copyright:
© Guy Avni, Thomas A. Henzinger, and Ðorđe Žikelić.


  • Bidding games
  • Mean-payoff games
  • Poorman bidding
  • Random-turn games
  • Richman bidding
  • Taxman bidding

ASJC Scopus subject areas

  • Software

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