A decentralized variable ordering method for distributed constraint optimization

  • Authors:
  • Anton Chechetka;Katia Sycara

  • Affiliations:
  • Carnegie Mellon University;Carnegie Mellon University

  • Venue:
  • Proceedings of the fourth international joint conference on Autonomous agents and multiagent systems
  • Year:
  • 2005

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Abstract

Many different multi-agent problems, such as distributed scheduling, can be formalized as distributed constraint optimization problems (DCOP [1]). Ordering the constraint variables is an important preprocessing step of the ADOPT algorithm [1], the state of the art method of solving DCOP. Currently ADOPT uses depth-first search (DFS) trees for that purpose. For certain classes of tasks DFS ordering does not exploit the problem structure as compared to pseudo-tree ordering [3]. Also the variables are currently ordered by using a centralized scheme, which requires global information about the problem structure.We present a variable ordering algorithm, which is both decentralized and makes use of pseudo-trees, thus exploiting the problem structure when possible. This allows to apply ADOPT to domains, where global information is unavailable, and find solutions more efficiently. The worst-case pseudo-tree depth resulting from our algorithm is √2k|V|, where V is the set of variables, and k is maximum cluster size in constraint graph. The algorithm has space and time complexity polynomial in size of the constraint graph.