Mobile Agents on Dynamic Graphs

Luna, Giuseppe Antonio Di

doi:10.1007/978-3-030-11072-7_20

Cited by 5 publications

(6 citation statements)

References 51 publications

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“…Exploration of static anonymous graphs using mobile robots has been studied for a very long time. A good survey on the topic is presented in [4], [6]. Exploration on anonymous graphs with 1-interval connected dynamism is relatively new and the first paper to study it in the current model is [7].…”

Section: B Related Workmentioning

confidence: 99%

“…We consider a 1-interval connected synchronous dynamic ring R of size n as considered in [6], [7]. As R is a ring, each node in R has two neighbours connected via two ports.…”

Section: Network Model and Assumptionsmentioning

confidence: 99%

“…This is slightly problematic as we require that there exists a phase in which robots can move for at least n steps, and we do not want to drastically increase the running time. An easy fix is to extend the number of rounds of each phase i by a constant factor, say 8, in order to ensure that on expectation and with high probability, the number of steps a robot moves through is at least 2 i when 2 i ≥ n. 6 For Stage 2 to occur, we need two robots to come into contact with each other and be marked A and B. Since the probability that two robots that were supposed to move through the same edge meet instead is 1/2, on expectation, at least one such meeting occurs within 2 phases of the first phase i where 2 i ≥ n. Thus, on expectation after O(n) rounds are complete, Stage 1 is over and Stage 2 begins.…”

Section: A Removing Edge Crossing Detectionmentioning

confidence: 99%

See 2 more Smart Citations

Live Exploration with Mobile Robots in a Dynamic Ring, Revisited

Mandal

Molla

Moses

2020

Algorithms for Sensor Systems

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The graph exploration problem requires a group of mobile robots, initially placed arbitrarily on the nodes of a graph, to work collaboratively to explore the graph such that each node is eventually visited by at least one robot. One important requirement of exploration is the termination condition, i.e., the robots must know that exploration is completed. The problem of live exploration of a dynamic ring using mobile robots was recently introduced in [Di Luna et al., ICDCS 2016]. In it, they proposed multiple algorithms to solve exploration in fully synchronous and semi-synchronous settings with various guarantees when 2 robots were involved. They also provided guarantees that with certain assumptions, exploration of the ring using two robots was impossible. An important question left open was how the presence of 3 robots would affect the results. In this paper, we try to settle this question in a fully synchronous setting and also show how to extend our results to a semi-synchronous setting.In particular, we present algorithms for exploration with explicit termination using 3 robots in conjunction with either (i) unique IDs of the robots and edge crossing detection capability (i.e., two robots moving in opposite directions through an edge in the same round can detect each other), or (ii) access to randomness. The time complexity of our deterministic algorithm is asymptotically optimal. We also provide complementary impossibility results showing that there does not exist any explicit termination algorithm for 2 robots even when each robot has a unique ID, edge crossing detection capability, and access to randomness. The theoretical analysis and comprehensive simulations of our algorithm show the effectiveness and efficiency of the algorithm in dynamic rings. We also present an algorithm to achieve exploration with partial termination using 3 robots with unique IDs in the semi-synchronous setting, when robots have access to edge crossing detection capability and randomness but do not know a bound on the size of the ring or have access to a landmark or are guaranteed that robots have common chirality. Our algorithms are fully decentralized, lightweight, and easily implementable.

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Section: B Related Workmentioning

confidence: 99%

“…We consider a 1-interval connected synchronous dynamic ring R of size n as considered in [6], [7]. As R is a ring, each node in R has two neighbours connected via two ports.…”

Section: Network Model and Assumptionsmentioning

confidence: 99%

Section: A Removing Edge Crossing Detectionmentioning

confidence: 99%

See 1 more Smart Citation

Live Exploration with Mobile Robots in a Dynamic Ring, Revisited

Mandal

Molla

Moses

2020

Algorithms for Sensor Systems

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“…While the study of mobile agents on static networks is really mature, and generated a copious literature (e.g., see [31] and chapters therein), the research on mobile agents in temporal graphs is still in its infancy, especially from a purely distributed perspective. Its focus has been on classical problems, such as graph exploration [6,18,32], gathering [7,19], scattering [3], and grouping [14] under a variety of settings, depending on the types of communication mechanisms employed by the agents, the topology of the network, etc., and under a variety of assumptions on the agents' knowledge and capabilities (for a recent detailed survey see [16]). In spite of the different settings, these investigations share a common trait: they assume that the dynamic network on which the agents operate is safe; i.e., there is no Bh.…”

Section: Introduction 1backgroundmentioning

confidence: 99%

Black Hole Search in Dynamic Rings

Luna

Flocchini

Prencipe

et al. 2021

2021 IEEE 41st International Conference on Distributed Computing Systems (ICDCS)

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In this paper, we start the investigation of distributed computing by mobile agents in dangerous dynamic networks. The danger is posed by the presence in the network of a black hole (Bh), a harmful site that destroys all incoming agents without leaving any trace. The problem of determining the location of the black hole in a network, known as black hole search (Bhs), has been extensively studied in the literature, but always and only assuming that the network is static. At the same time, the existing results on mobile agents computing in dynamic networks never consider the presence of harmful sites. In this paper we start filling this research gap by studying black hole search in temporal rings, specifically focusing on 1-interval connectivity adversarial dynamics.The main complexity parameter of Bhs is the number of agents (called size) needed to solve the problem; other parameters are the number of moves (called cost) performed by the agents, and the time until termination.Feasibility and complexity depend on many factors; the size n of the ring, whether or not n is known, and the type of inter-agent communication (whiteboards, tokens, face-to-face, visual). In this paper, we provide a complete feasibility characterization presenting size optimal algorithms. Furthermore, we establish lower bounds on the cost and time of size-optimal solutions and show that our algorithms achieve those bounds.

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“…Under weaker models of connectivity, the only problem ever studied, to the best of our knowledge, is a weaker version of the gathering, where all agents but one gather ( Bournat, Dubois & Petit, 2018 ). An up-to-date survey on computing by mobile agents on dynamic graph is in Di Luna (2019) .…”

Section: Introductionmentioning

confidence: 99%

Compacting oblivious agents on dynamic rings

Das

Luna

Mazzei

et al. 2021

PeerJ Computer Science

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In this paper we investigate dynamic networks populated by autonomous mobile agents. Dynamic networks are networks whose topology can change continuously, at unpredictable locations and at unpredictable times. These changes are not considered to be faults, but rather an integral part of the nature of the system. The agents can autonomously move on the network, with the goal of solving cooperatively an assigned common task. Here, we focus on a specific network: the unoriented ring. More specifically, we study 1-interval connected dynamic rings (i.e., at any time, at most one of the edges might be missing). The agents move according to the widely used Look–Compute–Move life cycle, and can be homogenous (thus identical) or heterogenous (agents are assigned colors from a set of c > 1 colors). For identical agents, their goal is to form a compact segment, where agents occupy a continuous part of the ring and no two agents occupy the same node: we call this the Compact Configuration Problem. In the case of agents with colors, called the Colored Compact Configuration Problem, the goal is to group agents such that each group is formed by all agents having the same color, it occupies a continuous segment of the network, and groups of agents having different colors occupy distinct areas of the network. In this paper we determine the necessary conditions to solve both proposed problems. For all solvable cases, we provide algorithms for both the monochromatic and the colored version of the compact configuration problem. All our algorithms work even for the simplest model where agents have no persistent memory, no communication capabilities and do not agree on a common orientation within the network. To the best of our knowledge this is the first work on the compaction problem in a dynamic network.

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Mobile Agents on Dynamic Graphs

Cited by 5 publications

References 51 publications

Live Exploration with Mobile Robots in a Dynamic Ring, Revisited

Live Exploration with Mobile Robots in a Dynamic Ring, Revisited

Black Hole Search in Dynamic Rings

Compacting oblivious agents on dynamic rings

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