This paper considers the problem of network structure manipulation in the absence of information on the global network topology. In particular, the problem of removing some of links is investigated in order to slow or...
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This paper considers the problem of network structure manipulation in the absence of information on the global network topology. In particular, the problem of removing some of links is investigated in order to slow or stop the spread of disease in a network while preserving its connectivity. Existing methods solve this combinatorial problem in a centralized manner and they require the global information of network structure. In this paper, we propose a distributed design algorithm to compute a suboptimal solution to this problem efficiently by mimicking gradient based method, namely by iteratively removing one or multiple links at a time from the network. Specifically, using matrix perturbation analysis we formulate an optimization problem involving the eigenvector associated with the largest eigenvalue of the adjacency matrix and whose solution is equal to a suboptimal solution to the original problem. This strategy also enables us to overcome the combinatorial issue of the problem. distributed algorithms to estimate the eigenvector and to verify network's connectivity are then proposed which facilitate us to solve the new optimization problem. In addition, topological insights into the proposed algorithm and optimality of its solution are also discussed. Finally, the proposed distributed design method is demonstrated and evaluated via several numerical examples.
We consider a multi-agent task assignment problem where a group of agents need to select tasks from their admissible task sets. The utility of an assignment profile is measured by the sum of individual task utilities,...
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We consider a multi-agent task assignment problem where a group of agents need to select tasks from their admissible task sets. The utility of an assignment profile is measured by the sum of individual task utilities, which is a submodular function of the set of agents that are assigned to it. The objective is to find an assignment profile that maximizes the global utility. This problem is NP-hard in general. In this paper we propose an algorithm that provides an assignment profile with utility at least 1/(1 + kappa) of the optimal utility, where kappa is an element of [0, 1] is a parameter for the curvature of the submodular utility functions. In the worst case, when kappa = 1, our algorithm achieves utility at least 1/2 of the optimal. Moreover, when the communication links between agents are consistent with the admissible task sets, the algorithm can be implemented distributedly and asynchronously, which means that there is no centralized coordinator and each agent selects its task using only local information and local communication based on its own time-clock. (C) 2019 Elsevier Ltd. All rights reserved.
The push-sum based subgradient is an important method for distributed convex optimization over unbalanced directed graphs, which is known to converge at a rate of $O\left( {\ln t/\sqrt t } \right)$. This paper shows t...
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ISBN:
(数字)9781665467612
ISBN:
(纸本)9781665467629
The push-sum based subgradient is an important method for distributed convex optimization over unbalanced directed graphs, which is known to converge at a rate of $O\left( {\ln t/\sqrt t } \right)$. This paper shows that the subgradient-push algorithm actually converges at a rate of $O\left( {1/\sqrt t } \right)$, which is the same as that of the single-agent subgradient and thus optimal. The proposed tool for analyzing push-sum based algorithms is of independent interest.
We propose a silent self-stabilizing asynchronous distributed algorithm to find a 2-minimal dominating set (2-MDS) in networks of girth at least 7. Given a graph $G=(V, E)$ , a 2-MDS of $G$ is a minimal dominating set...
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We propose a silent self-stabilizing asynchronous distributed algorithm to find a 2-minimal dominating set (2-MDS) in networks of girth at least 7. Given a graph $G=(V, E)$ , a 2-MDS of $G$ is a minimal dominating set $D\subseteq V$ such that $D\backslash \{p_{i},p_{j}\}\cup\{p_{z}\}$ is not a dominating set for any nodes $p_{i},p_{j}\in L (p_{i}\neq p_{j})$ and $p_{z}\ /{\!\!\!\in} D$ . The girth is the length of the shortest cycles in the graph. We assume that the processes have unique identifiers. The proposed algorithm constructs a 2-MDS in the networks of girth at least 7 under the weakly fair distributed daemon. The time complexity is $O(nH)$ rounds, and the space complexity is $O(\log n)$ bits per process, where $n$ is the number of processes and $H$ is the diameter of the network.
We investigate the vulnerabilities of consensus-based distributed optimization protocols to nodes that deviate from the prescribed update rule (e.g., due to failures or adversarial attacks). We first characterize cert...
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We investigate the vulnerabilities of consensus-based distributed optimization protocols to nodes that deviate from the prescribed update rule (e.g., due to failures or adversarial attacks). We first characterize certain fundamental limitations on the performance of any distributed optimization algorithm in the presence of adversaries. We then propose a secure distributed optimization algorithm that guarantees that the nonadversarial nodes converge to the convex hull of the minimizers of their local functions under the certain conditions on the graph topology, regardless of the actions of a certain number of the adversarial nodes. In particular, we provide sufficient conditions on the graph topology to tolerate a bounded number of adversaries in the neighborhood of every nonadversarial node, and necessary and sufficient conditions to tolerate a globally bounded number of adversaries. For situations, where there are up to F adversaries in the neighborhood of every node, we use the concept of maximal F-local sets of graphs to provide lower bounds on the distance-to-optimality of achievable solutions under any algorithm. We show that finding the size of such sets is NP-hard.
In this study, the solution of a convex distributed optimisation problem with a global coupling inequality constraint is considered. By using the Lagrange duality framework, the problem is transformed into a distribut...
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In this study, the solution of a convex distributed optimisation problem with a global coupling inequality constraint is considered. By using the Lagrange duality framework, the problem is transformed into a distributed consensus optimisation problem and then based on the recently proposed Hybrid Alternating Direction Method of Multipliers (H-ADMM), which merges distributed and centralised optimisation concepts problems, a novel distributed algorithm is developed. In particular, the authors offer a reformulation of the original H-ADMM in an operator theoretical framework, which exploits the known relationship between ADMM and Douglas-Rachford splitting. In addition, the authors' formulation allows us to generalise the H-ADMM by including a relaxation constant, not present in the original design of the algorithm. Moreover, an adaptive penalty parameter selection scheme that consistently improves the practical convergence properties of the algorithm is proposed. Finally, the convergence results of the proposed algorithm are discussed and moreover, in order to present the effectiveness and the major capabilities of the proposed algorithm in off-line and on-line scenarios, distributed quadratic programming and distributed model predictive control problems are considered in the simulation section.
This paper focuses on the multi-agent safe control problem for stochastic systems. We propose a probabilistic certificate for safety and performance specifications and use it to construct a distributed algorithm. The ...
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ISBN:
(数字)9781665467612
ISBN:
(纸本)9781665467629
This paper focuses on the multi-agent safe control problem for stochastic systems. We propose a probabilistic certificate for safety and performance specifications and use it to construct a distributed algorithm. The certificate integrates the reachability- and invariance-based (barrier-function-based) approaches via a new notion of forward invariance defined on the long-term probability. The proposed method has two features. First, it can guarantee a long-term probability of safety and performance satisfaction using myopic evaluation. Second, each agent can collaboratively ensure system-wide specifications even if each does not have sufficient information to evaluate the specifications. The effectiveness of the proposed method is tested using numerical experiments.
The vertex cover of networks is a classical combinatorial optimization problem. In this paper, we investigate the vertex cover problem solved by the memory-based best response update rule, which can not converge to a ...
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The vertex cover of networks is a classical combinatorial optimization problem. In this paper, we investigate the vertex cover problem solved by the memory-based best response update rule, which can not converge to a strict Nash equilibrium (SNE) with memory length m =3D 1. To overcome this shortcoming, a bounded rational behavioral (BRB) update rule is newly proposed in this paper. We prove that the BRB with m =3D 1 can guarantee that the whole vertices' state converges to a SNE. The simulation is carried out to verify that the performance of the proposed BRB update rule on representative networks. Moreover, we also find that a better SNE will be achieved by increasing the selection intensity.
Blockchain technology has become the hottest technology in the market because of its characteristics such as decentralization and data tamper resistance. With the development of blockchain, it is widely used in many f...
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Blockchain technology has become the hottest technology in the market because of its characteristics such as decentralization and data tamper resistance. With the development of blockchain, it is widely used in many fields. There are many types of blockchain, such as alliance chain, private chain and public chain. At present, the alliance chain has attracted extensive attention, but the commonly used PBFT algorithm still has many problems. In order to solve the high communication overhead and low efciency of PBFT consensus echanism, an improved PBFT consensus algorithm with a reputation mechanism are proposed in this paper. Diff erent permissions of nodes are made according to their diff erent reputation levels. Only the nodes with high reputation are qualifed to act as master nodes. Nodes with low reputation will be prohibited from participating in the consistency protocol and reduce the probability of becoming master nodes. In our scheme, the security, efciency and throughput of the consensus algorithm are improved, and the communication cost is reduced.
Highly dynamic networks are characterized by frequent changes in the availability of communication links. These networks are often partitioned into several components, which split and merge unpredictably. We present a...
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Highly dynamic networks are characterized by frequent changes in the availability of communication links. These networks are often partitioned into several components, which split and merge unpredictably. We present a distributed algorithm that maintains a forest of (as few as possible) spanning trees in such a network, with no restriction on the rate of change. Our algorithm is inspired by high-level graph transformations, which we adapt here in a (synchronous) message passing model for dynamic networks. The resulting algorithm has the following properties. First, every decision is purely localin each round, a node only considers its role and that of its neighbors in the tree, with no further information propagation (in particular, no wave mechanisms). Second, whatever the rate and scale of the changes, the algorithm guarantees that, by the end of every round, the network is covered by a forest of spanning trees in which (1) no cycle occur, (2) every node belongs to exactly one tree and (3) every tree contains exactly one root. We primarily focus on the correctness of this algorithm, which is established rigorously. While performance is not the main focus, we suggest new complexity metrics for such problems, and report on preliminary experimentation results validating our algorithm in a practical scenario.
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