Title

Examining Coordination Tradeoffs in Distributed Constraint Satisfaction Problems (DCSPs)

Date of Original Version

2005

Type

Working Paper

Rights Management

All Rights Reserved

Abstract or Description

Distributed Constraint Satisfaction Problems (DCSPs) provide a model to capture a broad range of cooperative multi-agent problem solving settings. Researchers have generally pro- posed two different sets of approaches for solving DCSPs, backtracking based approaches, such as Asynchronous Backtracking (ABT), and mediation based approaches, such as Asyn- chronous Partial Overlay (APO). These sets of approaches differ in the levels of coordination employed during conflict resolution. While the computational and communication complex- ity of the backtracking based approaches is well understood, the tradeoffs in complexity involved in moving toward mediation based approaches are not. In this paper we com- prehensively reexamine the space of mediation based approaches for DCSP and fill gaps in existing frameworks with new strategies. We present different mediation session selec- tion rules, including a rule that favors smaller mediation sessions, and different mediation strategies, including a decentralized hybrid strategy based on ABT. We present empirical re- sults on solvable 3-coloring and random binary DCSP problems, that accurately capture the computational and communication tradeoffs between ABT and various mediation based ap- proaches. Our results confirm that under some circumstances the newly presented strategies dominate previously proposed techniques.