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作者： Talal Riaz University of Iowa

学位级别：博士

A fundamental issue in many distributed computing problems is the need for nodes to distinguish themselves from their neighbors in a process referred to as symmetry breaking. Many well-known problems such as Maximal Independent Set (MIS), t-Ruling Set, Maximal Matching, and (\Delta+1)-Coloring, belong to the class of problems that require symmetry breaking. These problems have been studied extensively in the LOCAL model, which assumes arbitrarily large message sizes, but not as much in the CONGEST and k-machine models, which assume messages of size O(log n) bits. This dissertation focuses on finding upper and lower bounds for symmetry breaking problems, such as MIS and t-Ruling Set, in these congested models. Chapter 2 shows that an MIS can be computed in O(sqrt{log n loglog n}) rounds for graphs with constant arboricity in the CONGEST model. Chapter 3 shows that the t-ruling set problem, for t \geq 3, can be computed in o(log n) rounds in the CONGEST model. Moreover, it is shown that a 2-ruling set can be computed in o(log n) rounds for a large range of values of the maximum degree in the graph. In the k-machine model, k machines must work together to solve a problem on an arbitrary n-node graph, where n is typically much larger than k. Chapter 4 shows that any algorithm in the BEEP model (which assumes 'primitive' single bit messages) with message complexity M and round complexity T can be simulated in O(t(M/k^2 + T) poly(log n)) rounds in the k-machine model. Using this result, it is shown that MIS, Minimum Dominating Set (MDS), and Minimum Connected Dominating Set (MCDS) can all be solved in O(poly(log n) m/k^2) rounds in the k-machine model, where 'm' is the number of edges in the input graph. It is shown that a 2-ruling set can be computed even faster, in O((n/k^2+ k) poly(log n)) rounds, in the k-machine model. On the other hand, using information theoretic techniques and a reduction to a communication complexity problem, an \Omega(n/(k^2 poly(log n))) rounds

关键词： distributed algorithms distributed Systems Graph Theory Information Theory Maximal Independent Set Modes of Computation

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Randomized Experimental Design via Geographic Clustering 19

Randomized Experimental Design via Geographic Clustering

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25th ACM SIGKDD International Conference on Knowledge Discovery & Data Mining (KDD)

作者： Rolnick, David Aydin, Kevin Pouget-Abadie, Jean Kamali, Shahab Mirrokni, Vahab Najmi, Amir Univ Penn Philadelphia PA 19104 USA Google Res Mountain View CA USA

ISBN: (纸本)9781450362016

Web-based services often run randomized experiments to improve their products. A popular way to run these experiments is to use geographical regions as units of experimentation, since this does not require tracking of individual users or browser cookies. Since users may issue queries from multiple geographical locations, georegions cannot be considered independent and interference may be present in the experiment. In this paper, we study this problem, and first present GeoCUTS, a novel algorithm that forms geographical clusters to minimize interference while preserving balance in cluster size. We use a random sample of anonymized traffic from Google Search to form a graph representing user movements, then construct a geographically coherent clustering of the graph. Our main technical contribution is a statistical framework to measure the effectiveness of clusterings. Furthermore, we perform empirical evaluations showing that the performance of GeoCUTS is comparable to hand-crafted geo-regions with respect to both novel and existing metrics.

关键词： geographic clustering balanced partitioning distributed algorithms causal inference A/B testing violations of SUTVA

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BlockCom: A Blockchain based Commerce Model for Smart Communities using Auction Mechanism

BlockCom: A Blockchain based Commerce Model for Smart Commun...

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IEEE International Conference on Communications (IEEE ICC)

作者： Hassija, Vikas Bansal, Gaurang Chamola, Vinay Saxena, Vikas Sikdar, Biplab JIIT Dept Comp Sci & Engn Noida Campus Noida India BITS Pilani Dept Elect & Elect Engn Pilani Campus Pilani Rajasthan India Natl Univ Singapore Dept Elect & Comp Engn Singapore Singapore

ISBN: (纸本)9781728123738

Smart Communities seeks to thrive in a context of broadband economy, its engine and reason for being. The success of any community is a function of its economic backbone or the supply chain. A supply chain can be defined as the integration of customers, retailers, distributors and manufacturers. The changing technology has made the survival in commerce highly competitive and price sensitive. Blockchain technology can be the game-changer for decentralizing infrastructure and building a trust layer for business logic. BlockCom is a commerce model based on the emerging technology of blockchain. This paper presents a double auction scheme for energy trading between customers and suppliers. A smart contract implements a distributed algorithm to maximize individual participating profit. Parties bid to smart contract which act as auctioneer for maximizing the profit. Mathematical parameter named credibility score has been created to deal with trust issues in the decentralized network using byzantine fault tolerant mechanism. BlockCom provides a fresh perspective on the concept of supply chain and commerce.

关键词： Commerce Energy trading Auctioneers contract supply chain DISTRIBUTOR distributed algorithms Engines Purchasing

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Uniform Consensus Prone to Omission Failures with Fault Knowledge 24

Uniform Consensus Prone to Omission Failures with Fault Know...

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IEEE 24th Pacific Rim International Symposium on Dependable Computing (PRDC)

作者： Cao, Xiao Chinese Acad Sci Inst Comp Technol Beijing Peoples R China

ISBN: (纸本)9781728149615

As for uniform consensus prone to omission failures, there are t+1 (t is the number of faulty nodes) round tight lower bound and left perpendicular1/2right perpendicular-1 fault tolerance tight upper bound [6,7]. However, the unreachable n/2 upper bound is based on a hidden condition that it's impossible for all the nodes to know whether they are faulty or not. Few papers focused on this issue. This paper asks two vital questions about it: can nodes know they are faulty or not and what will happen if they have such fault knowledge. Some new findings are made including: (1) This condition is true if only message passing is available;(2) With receive and send fault knowledge, the fault tolerance tight upper bound is n;(3) Still, with only receive fault knowledge, the fault tolerance tight upper bound is n-1;(4) Finally if only send fault knowledge is available, the fault tolerance upper bound is smaller than 2n/3.

关键词： uniform consensus omission failure fault knowledge impossibilities distributed algorithms

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Computation Time Analysis of Centralized and distributed Optimization algorithms Applied to Automated Irrigation Networks 3rd

Computation Time Analysis of Centralized and Distributed Opt...

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3rd Australian Control Conference (AUCC)

作者： Farhadi, Alireza Dower, Peter M. Cantoni, Michael Sharif Univ Technol Dept Elect Engn Tehran Iran Univ Melbourne Dept Elect & Elect Engn Melbourne Vic 3010 Australia

ISBN: (纸本)9781479924981;9781479924974

This paper compares the computation time of two algorithms for solving a structured constrained linear optimal control problem with finite horizon quadratic cost within the context of automated irrigation networks. The first is a standard centralized algorithm based on the active set method that does not exploit problem structure. The second is distributed and is based on a consensus algorithm, not specifically tailored to account for system structure. It is shown that there is a significant advantage in terms of computation overhead (the time spent computing the optimal solution) in using the second algorithm in large-scale networks. Specifically, for a fixed horizon length the computation overhead of the centralized algorithm grows as O(n(5)) with the number n of sub-systems. By contrast, it is observed via a combination of analysis and experiment that given n times resources for computation the computation overhead of the distributed algorithm grows as O(n) with the number n of sub-systems.

关键词： complex networks computational complexity distributed algorithms irrigation optimal control optimisation set theory

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Chauffeuring a Crashed Robot from a Disk 15th

Chauffeuring a Crashed Robot from a Disk

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15th International Symposium on algorithms and Experiments for Wireless Sensor Networks (ALGOSENSORS) as part of the ALGO Conference

作者： Pattanayak, Debasish Ramesh, H. Mandal, Partha Sarathi Indian Inst Technol Guwahati Gauhati India

ISBN: (纸本)9783030344054;9783030344047

Evacuation of robots from a disk has recently attained a lot of attention. We visit the problem from the perspective of fault-tolerance. We consider two robots trying to evacuate from a disk via a single hidden exit on the perimeter of the disk. The robots communicate wirelessly. The robots are susceptible to crash faults, after which they stop moving and communicating. We design the algorithms for tolerating one fault. The objective is to minimize the worst-case time required to evacuate both the robots from the disk. When the non-faulty robot chauffeurs the crashed robot, it takes alpha >= 1 amount of time to travel unit distance. With this, we also provide a lower bound for the evacuation time. Further, we evaluate the worst-case of the algorithms for different values of alpha and the crash time.

关键词： Evacuation Mobile robots Crash faults distributed algorithms

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On distributed Scheduling of Flexible Demand and Nash Equilibria in the Electricity Market

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DYNAMIC GAMES AND APPLICATIONS 2018年第4期8卷 761-798页

作者： De Paola, Antonio Angeli, David Strbac, Goran Imperial Coll London Dept Elect & Elect Engn South Kensington Campus London SW7 2AZ England

This paper presents a novel game theory approach for large-scale deployment of price-responsive electrical appliances. In the proposed distributed control scheme, each appliance independently schedules its power consumption on the basis of a broadcast demand/price signal, aiming to complete its task at minimum cost. The conflicting interactions of the appliances, competing for power consumption at the cheapest hours of the day, are modelled through a differential game with a continuum of players, and efficient deployment of flexible demand is characterized as a Nash equilibrium. A novel approach is adopted to derive necessary and sufficient equilibrium conditions: intrinsic properties of the problem (price monotonicity, unidirectionality of power transfers) are exploited to perform an equilibrium study based on sublevel sets of the considered demand profiles. As a result, it is possible to determine for which penetration levels of flexible demand, types of appliances and inflexible demand profiles it is possible to achieve an equilibrium. Such stable configuration is achieved through the broadcast of a single demand/price signal and does not require iterated exchange of information between devices and coordinator. In addition, the global optimality of the equilibrium is proved, necessary conditions for Pareto optimality are derived, and a preliminary analysis of devices with partial time availability is carried out. The performance of the proposed control strategy is evaluated in simulation, considering realistic future scenarios of the UK power system with large penetration of flexible demand.

关键词： Smart grid distributed algorithms Price-responsive appliances Electricity market Differential games

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Designing linear distributed algorithms with memory for fast convergence

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INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL 2012年第15期22卷 1691-1702页

作者： Roy, Sandip Wan, Yan Saberi, Ali Xue, Mengran Washington State Univ Dept Elect Engn Pullman WA 99164 USA Univ N Texas Dept Elect Engn Denton TX 76203 USA

Motivated by both distributed computation and decentralized control applications, we studied the distributed linear iterative algorithms with memory. Specifically, we showed that the system of linear equations Gx = b b can be solved through a distributed linear iteration for arbitrary invertible G using only a single memory element at each processor. Further, we demonstrated that the memoried distributed algorithm can be designed to achieve much faster convergence than a memoryless distributed algorithm. Two small simulation examples were included to illustrate the results. Copyright (c) 2011 John Wiley & Sons, Ltd.

关键词： distributed algorithms large-scale networks decentralized control theory numerical algorithms

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Flight Coordination Approaches of UAV Squads for WSN Data Collection

Flight Coordination Approaches of UAV Squads for WSN Data Co...

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作者： Bruno Jose Olivieri de Souza Pontificia Universidade Catolica do Rio de Janeiro

学位级别：博士

Olivieri de Souza, Bruno Jose; Endler, Markus (Advisor). Flight Coordination Approaches of UA V Squads for WSN Data Collection. Rio de Janeiro, 2019. 111p. Tese de doutorado – Departamento de Informatica, Pontificia Universidade Catolica do Rio de Janeiro. Wireless sensor networks (WSNs) are an important means of collecting data in a variety of situations, such as monitoring large or hazardous areas. The retrieval of WSN data can yield better results with the use of unmanned aerial vehicles (UAVs), for example, concerning the increase in the amount of collected data and decrease in the time between the collection and use of the data. In particular, disaster areas may be left without communication resources and with great residual risk to humans, at which point a WSN can be quickly launched by air to collect relevant data until other measures can be put in place. Some studies present approaches to the use of UAVs for the collection of WSN data, focusing mainly on optimizing the path to be covered by a single UAV and relying on long-range communication that is always available; these studies do not explore the possibility of using several UAVs or the limitations on the range of communication. This work describes DADCA, a distributed scalable approach capable of coordinating groups of UAVs in WSN data collection with restricted communication range and without the use of optimization techniques. The results show that the amount of data collected by DADCA is similar or superior, by up to 1%, to path optimization approaches. In the proposed approach, the delay in receiving sensor messages is up to 46% shorter than in other approaches, and the required processing onboard UAVs can reach less than 75% of those using optimization-based algorithms. The results indicate that the DADCA can match and even surpass other approaches presented, while also adding the advantages of a distributed approach.

关键词： Unmanned Aereal Vehicles Data Collection Wireles Sensors Networks distributed algorithms Swarm

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Evacuation from a Finite 2D Square Grid Field by a Metamorphic Robotic System

Evacuation from a Finite 2D Square Grid Field by a Metamorph...

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International Symposium on Computing and Networking (CANDAR)

作者： Junya Nakamura Sayaka Kamei Yukiko Yamauchi Information and Media Center Toyohashi University of Technology Aichi Japan Graduate School of Advanced Science and Engineering Hiroshima University Hiroshima Japan Graduate School of Information Science and Electrical Engineering Kyushu University Fukuoka Japan

ISBN: (数字)9781728182216

ISBN: (纸本)9781728182223

We consider evacuation from a finite two-dimensional (2D) square grid field by a metamorphic robotic system (MRS). An MRS is composed of anonymous memoryless modules. Each module of an MRS executes an identical distributed algorithm and moves autonomously while keeping the connectivity of modules. Since the modules are memoryless, an MRS utilizes its shape to remember the progress of execution. The number of available shapes that an MRS can form depends on the number of modules, which is thus an important complexity measure for a behavior of an MRS. In this paper, we investigate the minimum number of modules required to solve the evacuation problem with several conditions. First, we consider a rectangular field surrounded by walls with at least one exit and show that two modules are necessary and sufficient for evacuation from any rectangular field if the modules are equipped with a global compass, which allows the modules to have a common sense of direction. Then, we focus on the case where modules do not have a global compass and show that four (resp. seven) modules are necessary and sufficient for restricted (resp. any) initial states of an MRS. We also show that two modules are sufficient in the special case where an MRS is on a wall in an initial configuration. Finally, we extend these results to another type of fields, that is, mazes.

关键词： Shape Shape measurement Two dimensional displays Turning Compass distributed algorithms Robots

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