Title
Tree exploration with logarithmic memory
Abstract
We consider the task of network exploration by a mobile agent (robot) with small memory. The agent has to traverse all nodes and edges of a network (represented as an undirected connected graph), and return to the starting node. Nodes of the network are unlabeled and edge ports are locally labeled at each node. The agent has no a priori knowledge of the topology of the network or of its size, and cannot mark nodes in any way. Under such weak assumptions, cycles in the network may prevent feasibility of exploration, hence we restrict attention to trees. We present an algorithm to accomplish tree exploration (with return) using O(log n)-bit memory for all n-node trees. This strengthens the result from Diks et al. [2004], where O(log 2 n)-bit memory was used for tree exploration, and matches the lower bound on memory size proved there. We also extend our O(log n)-bit memory traversal mechanism to a weaker model in which ports at each node are ordered in circular manner, however, the explicit values of port numbers are not available.
Year
DOI
Venue
2011
10.1145/1921659.1921663
ACM Transactions on Algorithms
Keywords
Field
DocType
circular manner,network exploration,bit memory,n-node tree,mobile agent,memory size,bit memory traversal mechanism,logarithmic memory,log n,tree exploration,graph exploration,distributed algorithms,small memory,connected graph,lower bound,a priori knowledge,distributed algorithm
Discrete mathematics,Binary logarithm,Combinatorics,Tree traversal,Computer science,Upper and lower bounds,Mobile agent,Distributed algorithm,Logarithm,Connectivity,Traverse
Journal
Volume
Issue
ISSN
7
2
1549-6325
Citations 
PageRank 
References 
11
0.56
27
Authors
5
Name
Order
Citations
PageRank
Christoph Ambühl135718.50
leszek gasieniec238327.22
Andrzej Pelc33416246.55
Tomasz Radzik4109895.68
Xiaohui Zhang5110.56