Justifying and Improving Meta-Agent Conflict-Based Search

The Meta-Agent Conflict-Based Search~(MA-CBS) is a recently proposed algorithm for the multi-agent path finding problem. The algorithm is an extension of Conflict-Based Search~(CBS), which automatically merges conflicting agents into meta-agents if the number of conflicts exceeds a certain threshold. However, the decision to merge agents is made according to an empirically chosen fixed threshold on the number of conflicts. The best threshold depends both on the domain and on the number of agents, and the nature of the dependence is not clearly understood. We suggest a justification for the use of a fixed threshold on the number of conflicts based on the analysis of a model problem. Following the suggested justification, we introduce new decision policies for the MA-CBS algorithm, which considerably improve the algorithm's performance. The improved variants of the algorithm are evaluated on several sets of problems, chosen to underline different aspects of the algorithms.

[1]  Roni Stern,et al.  The Increasing Cost Tree Search for Optimal Multi-Agent Pathfinding , 2011, IJCAI.

[2]  A. James.  2010 , 2011, Philo of Alexandria: an Annotated Bibliography 2007-2016.

[3]  Anna R. Karlin,et al.  Competitive randomized algorithms for non-uniform problems , 1990, SODA '90.

[4]  Nathan R. Sturtevant,et al.  Benchmarks for Grid-Based Pathfinding , 2012, IEEE Transactions on Computational Intelligence and AI in Games.

[5]  Lyle A. McGeoch,et al.  Competitive algorithms for on-line problems , 1988, STOC '88.

[6]  W. W. Johnson,et al.  Notes on the "15" Puzzle , 1879 .

[7]  Manfred K. Warmuth,et al.  Finding a Shortest Solution for the N × N Extension of the 15-PUZZLE Is Intractable , 1986, AAAI.

[8]  Trevor Scott Standley.  Finding Optimal Solutions to Cooperative Pathfinding Problems , 2010, AAAI.

[9]  Roni Stern,et al.  Suboptimal Variants of the Conflict-Based Search Algorithm for the Multi-Agent Pathfinding Problem , 2014, SOCS.

[10]  Nathan R. Sturtevant,et al.  Meta-Agent Conflict-Based Search For Optimal Multi-Agent Path Finding. , 2012 .

[11]  Richard E. Korf,et al.  Complete Algorithms for Cooperative Pathfinding Problems , 2011, IJCAI.

[12]  Richard E. Korf,et al.  Depth-First Iterative-Deepening: An Optimal Admissible Tree Search , 1985, Artif. Intell..

[13]  Anna R. Karlin,et al.  Competitive snoopy caching , 1986, 27th Annual Symposium on Foundations of Computer Science (sfcs 1986).

[14]  Nathan R. Sturtevant,et al.  Conflict-based search for optimal multi-agent pathfinding , 2012, Artif. Intell..

[15]  Adi Botea,et al.  On Improving the Quality of Solutions in Large-Scale Cooperative Multi-Agent Pathfinding , 2011, SOCS.

[17]  Robert C. Holte,et al.  Steps Towards The Automatic Creation of Search Heuristics , 2004 .

[18]  Stuart J. Russell,et al.  Rationality and Intelligence: A Brief Update , 2013, PT-AI.

[19]  Nathan R. Sturtevant,et al.  Partial-Expansion A* with Selective Node Generation , 2012, SOCS.

[20]  E. KorfRichard.  Depth-first iterative-deepening: an optimal admissible tree search , 1985 .

[21]  David Silver,et al.  Cooperative Pathfinding , 2005, AIIDE.