TY - GEN
T1 - Euler tour lock-in problem in the rotor-router model
T2 - 23rd International Symposium on Distributed Computing, DISC 2009
AU - Bampas, Evangelos
AU - Ga̧sieniec, Leszek
AU - Hanusse, Nicolas
AU - Ilcinkas, David
AU - Klasing, Ralf
AU - Kosowski, Adrian
PY - 2009
Y1 - 2009
N2 - The rotor-router model, also called the Propp machine, was first considered as a deterministic alternative to the random walk. It is known that the route in an undirected graph G=(V,E), where |V|=n and |E|=m, adopted by an agent controlled by the rotor-router mechanism forms eventually an Euler tour based on arcs obtained via replacing each edge in G by two arcs with opposite direction. The process of ushering the agent to an Euler tour is referred to as the lock-in problem. In recent work [11] Yanovski et al. proved that independently of the initial configuration of the rotor-router mechanism in G the agent locks-in in time bounded by 2mD, where D is the diameter of G. In this paper we examine the dependence of the lock-in time on the initial configuration of the rotor-router mechanism. The case study is performed in the form of a game between a player intending to lock-in the agent in an Euler tour as quickly as possible and its adversary with the counter objective. First, we observe that in certain (easy) cases the lock-in can be achieved in time O(m). On the other hand we show that if adversary is solely responsible for the assignment of ports and pointers, the lock-in time Ω(m•D) can be enforced in any graph with m edges and diameter D. Furthermore, we show that if provides its own port numbering after the initial setup of pointers by , the complexity of the lock-in problem is bounded by O(m • min {logm,D}). We also propose a class of graphs in which the lock-in requires time Ω(m •logm). In the remaining two cases we show that the lock-in requires time Ω(m •D) in graphs with the worst-case topology. In addition, however, we present non-trivial classes of graphs with a large diameter in which the lock-in time is O(m).
AB - The rotor-router model, also called the Propp machine, was first considered as a deterministic alternative to the random walk. It is known that the route in an undirected graph G=(V,E), where |V|=n and |E|=m, adopted by an agent controlled by the rotor-router mechanism forms eventually an Euler tour based on arcs obtained via replacing each edge in G by two arcs with opposite direction. The process of ushering the agent to an Euler tour is referred to as the lock-in problem. In recent work [11] Yanovski et al. proved that independently of the initial configuration of the rotor-router mechanism in G the agent locks-in in time bounded by 2mD, where D is the diameter of G. In this paper we examine the dependence of the lock-in time on the initial configuration of the rotor-router mechanism. The case study is performed in the form of a game between a player intending to lock-in the agent in an Euler tour as quickly as possible and its adversary with the counter objective. First, we observe that in certain (easy) cases the lock-in can be achieved in time O(m). On the other hand we show that if adversary is solely responsible for the assignment of ports and pointers, the lock-in time Ω(m•D) can be enforced in any graph with m edges and diameter D. Furthermore, we show that if provides its own port numbering after the initial setup of pointers by , the complexity of the lock-in problem is bounded by O(m • min {logm,D}). We also propose a class of graphs in which the lock-in requires time Ω(m •logm). In the remaining two cases we show that the lock-in requires time Ω(m •D) in graphs with the worst-case topology. In addition, however, we present non-trivial classes of graphs with a large diameter in which the lock-in time is O(m).
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U2 - 10.1007/978-3-642-04355-0_44
DO - 10.1007/978-3-642-04355-0_44
M3 - Conference contribution
AN - SCOPUS:76649137565
SN - 3642043542
SN - 9783642043543
T3 - Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
SP - 423
EP - 435
BT - Distributed Computing - 23rd International Symposium, DISC 2009, Proceedings
Y2 - 23 September 2009 through 25 September 2009
ER -