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asynchronous algorithm for integration of reaction-diffusion equations for inhomogeneous excitable media

CHAOS 2000年第4期10卷 812-825页

作者： Rousseau, G Kapral, R Univ Toronto Dept Chem Chem Phys Theory Grp Toronto ON M5S 3H6 Canada

An asynchronous algorithm for the integration of reaction-diffusion equations for inhomogeneous excitable media is described. Since many physical systems are inhomogeneous where either the local kinetics or the diffusion or conduction properties vary significantly in space, integration schemes must be able to account for wide variations in the temporal and spatial scales of the solutions. The asynchronous algorithm utilizes a fixed spatial grid and automatically adjusts the time step locally to achieve an efficient simulation where the errors in the solution are controlled. The scheme does not depend on the specific form of the local kinetics and is easily applied to systems with complex geometries. (C) 2000 American Institute of Physics. [S1054- 1500(00)00304-9].

关键词： asynchronous algorithm inhomogeneous excitable media integration physical systems geometries

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asynchronous algorithm for Distributed Multi-agent Convex Optimization 39

Asynchronous Algorithm for Distributed Multi-agent Convex Op...

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39th Chinese Control Conference (CCC)

作者： Zhao, Duqiao Liu, Ding Zhang, Xia Xian Univ Technol Natl & Local Joint Engn Res Ctr Crystal Growth Eq Xian 710048 Peoples R China Shaanxi Key Lab Complex Syst Control & Intelligen Xian 710048 Peoples R China

ISBN: (纸本)9789881563903

This paper proposes an asynchronous algorithm for distributed optimization problem (Asy-DOP) in multi-agent network with gradient noise. The algorithm can be implemented in an asynchronous distributed way. The objective function of the algorithm is the sum of the local functions of multiple nodes in the network, each node only knows its own local objective function and can exchange information with its neighbors. In addition, the algorithm is based on the undirected connected graph and requires the objective function is Lipschitz continuous. The step-size of the proposed algorithm is homogeneous and when the step-size is in a suitable range, it is proved that the convergence rate of the proposed algorithm is O(1/root k), where the k is the number of iterations.

关键词： asynchronous algorithm distributed optimization multi-agent gradient method

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Distributed Clock Skew and Offset Estimation in Wireless Sensor Networks: asynchronous algorithm and Convergence Analysis

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2013年第11期12卷 5908-5917页

作者： Du, Jian Wu, Yik-Chung Univ Hong Kong Dept Elect & Elect Engn Hong Kong Hong Kong Peoples R China

In this paper, we propose a fully distributed algorithm for joint clock skew and offset estimation in wireless sensor networks based on belief propagation. In the proposed algorithm, each node can estimate its clock skew and offset in a completely distributed and asynchronous way: some nodes may update their estimates more frequently than others using outdated message from neighboring nodes. In addition, the proposed algorithm is robust to random packet loss. Such algorithm does not require any centralized information processing or coordination, and is scalable with network size. The proposed algorithm represents a unified framework that encompasses both classes of synchronous and asynchronous algorithms for network-wide clock synchronization. It is shown analytically that the proposed asynchronous algorithm converges to the optimal estimates with estimation mean-square-error at each node approaching the centralized Cramer-Rao bound under any network topology. Simulation results further show that the convergence speed is faster than that corresponding to a synchronous algorithm.

关键词： Clock synchronization wireless sensor network factor graph asynchronous algorithm

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A Simplified Form of Block-Iterative Operator Splitting and an asynchronous algorithm Resembling the Multi-Block Alternating Direction Method of Multipliers

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JOURNAL OF OPTIMIZATION THEORY AND APPLICATIONS 2017年第1期173卷 155-182页

作者： Eckstein, Jonathan Rutgers State Univ Dept Management Sci & Informat Syst MSIS 100 Rockafeller RdLivingston Campus Piscataway NJ 08854 USA Rutgers State Univ RUTCOR 100 Rockafeller RdLivingston Campus Piscataway NJ 08854 USA

This paper develops what is essentially a simplified version of the block-iterative operator splitting method already proposed by the author and P. Combettes, but with more general initialization conditions. It then describes one way of implementing this algorithm asynchronously under a computational model inspired by modern high-performance computing environments, which consist of interconnected nodes each having multiple processor cores sharing a common local memory. The asynchronous implementation framework is then applied to derive an asynchronous algorithm which resembles the alternating direction method of multipliers with an arbitrary number of blocks of variables. Unlike earlier proposals for asynchronous variants of the alternating direction method of multipliers, the algorithm relies neither on probabilistic control nor on restrictive assumptions about the problem instance, instead making only standard convex-analytic regularity assumptions. It also allows the proximal parameters to range freely between arbitrary positive bounds, possibly varying with both iterations and subproblems.

关键词： asynchronous algorithm Convex optimization Alternating direction method of multipliers (ADMM)

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Comments on a Simplified Form of Block-Iterative Operator Splitting, and an asynchronous algorithm Resembling the Multi-block Alternating Direction Method of Multipliers

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JOURNAL OF OPTIMIZATION THEORY AND APPLICATIONS 2018年第3期176卷 783-785页

This note gives an improved version of the proof of Proposition 4.2 in "A Simplified Form of Block-Iterative Operator Splitting, and an asynchronous algorithm Resembling the Multi-block Alternating Direction Meth... 详细信息

关键词： asynchronous algorithm Convex optimization Alternating direction method of multipliers (ADMM)

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A distributed asynchronous algorithm for the two-stage stochastic unit commitment problem

A distributed asynchronous algorithm for the two-stage stoch...

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General Meeting of the IEEE-Power-and-Energy-Society

作者： Aravena, Ignacio Papavasiliou, Anthony UCL CORE London England

ISBN: (纸本)9781467380409

We present a distributed asynchronous algorithm for solving the two-stage stochastic unit commitment problem. The algorithm uses Lagrangian relaxation to decompose the problem by scenarios and applies an incremental method to solve the dual problem. At each incremental dual iteration, the algorithm evaluates the dual function, providing a lower bound, and recovers a feasible commitment for first stage units, which (through a feasibility recovery process) results in an upper bound. Both the incremental dual iterations as well as the feasibility recovery are executed asynchronously, resulting in more efficient utilization of parallel processors. The method is tested on a model of the Central Western European system, for which it achieved convergence three times faster than an equivalent distributed synchronous algorithm.

关键词： stochastic unit commitment incremental subgradient method asynchronous algorithm distributed optimization

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asynchronous algorithm for Distributed Multi-agent Convex Optimization

Asynchronous Algorithm for Distributed Multi-agent Convex Op...

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第三十九届中国控制会议

作者： Duqiao Zhao Ding Liu Xia Zhang National & Local Joint Engineering Research Center of Crystal Growth Equipment and System Integration Xi'an University of Technology Shaanxi Key Laboratory of Complex System Control and Intelligent Information Processing

This paper proposes an asynchronous algorithm for distributed optimization problem(Asy-DOP) in multi-agent network with gradient *** algorithm can be implemented in an asynchronous distributed *** objective function of the algorithm is the sum of the local functions of multiple nodes in the network,each node only knows its own local objective function and can exchange information with its *** addition,the algorithm is based on the undirected connected graph and requires the objective function is Lipschitz *** step-size of the proposed algorithm is homogeneous and when the step-size is in a suitable range,it is proved that the convergence rate of the proposed algorithm is O(1/(?)),where the k is the number of iterations.

关键词： asynchronous algorithm distributed optimization multi-agent gradient method

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A CHAOTIC asynchronous algorithm FOR COMPUTING THE FIXED-POINT OF A NONNEGATIVE MATRIX OF UNIT SPECTRAL-RADIUS

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JOURNAL OF THE ACM 1986年第1期33卷 130-150页

作者： LUBACHEVSKY, B MITRA, D AT&T Bell Labs Murray Hill NJ AT&T Bell Labs Murray Hill NJ

Given a nonnegative, irreducible matrix P of spectral radius unity, there exists a positive vector π such that π = πP. If P also happens to be stochastic, then π gives the stationary distribution of the Markov chain that has state-transition probabilities given by the elements of P. This paper gives an algorithm for computing π that is particularly well suited for parallel processing. The main attraction of our algorithm is that the timing and sequencing restrictions on individual processors are almost entirely eliminated and, consequently, the necessary coordination between processors is negligible and the enforced idle time is also *** certain mild and easily satisfied restrictions on P and on the implementation of the algorithm, x(.), the vectors of computed values are proved to converge to within a positive, finite constant of proportionality of π. It is also proved that a natural measure of the projective distance of x(.) from π vanishes geometrically fast, and at a rate for which a lower bound is given. We have conducted extensive experiments on random matrices P, and the results show that the improvement over the parallel implementation of the synchronous version of the algorithm is substantial, sometimes exceeding the synchronization penalty to which the latter is always subject.

关键词： asynchronous algorithm chaotic algorithm fixed point Markov chains

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A distributed asynchronous algorithm for the two-stage stochastic unit commitment problem

A distributed asynchronous algorithm for the two-stage stoch...

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IEEE Power and Energy Society General Meeting

作者： Ignacio Aravena Anthony Papavasiliou CORE UCL

ISBN: (纸本)9781467380416

关键词： Stochastic unit commitment Incremental sub-gradient method asynchronous algorithm Distributed optimization machine unit asynchronous Unit commitment Incremental Distribute BIFUNCTIONAL Stochastic iterative methods algorithms Dual Upper bound

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Delay Compensated asynchronous Adam algorithm for Deep Neural Networks 15

Delay Compensated Asynchronous Adam Algorithm for Deep Neura...

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15th IEEE International Symposium on Parallel and Distributed Processing with Applications (ISPA) / 16th IEEE International Conference on Ubiquitous Computing and Communications (IUCC)

作者： Shan, Lei Guan, Naiyang Yang, Canqun Xu, Weixia Zhang, Minxuan Natl Univ Def Technol Coll Comp Inst Software Changsha 410073 Hunan Peoples R China Natl Univ Def Technol Coll Comp Inst Comp Changsha 410073 Hunan Peoples R China

ISBN: (纸本)9781538637906

Deep neural network (DNN) learns hierarchical representations from big data in a multilayer network structure and has achieved great successes in many fields such as computer vision and speech analysis. Since DNN usually contains several billions of parameters, the asynchronous stochastic gradient descent (ASGD) algorithm is often used to train an effective DNN model on a computer cluster. However, as the increase of computing nodes and data size, ASGD suffers from serious slow convergence deficiency because the parameters might be wrongly updated by long-term delayed gradients. In this paper, we propose a delay compensated asynchronous Adam (DC-Adam) algorithm to train DNN. In particular, DC-Adam updates the parameters with the moment increment which is the division of the first and the second moments to take the advantage of the original Adam algorithm, and compensates the gradient with the first-order component in its Taylor expansion. Since the delay compensation technique reduces the error of delayed gradients, and the moment increment further counteracts the influence of approximated compensation, DC-Adam converges much more rapidly than ASGD on a computer cluster with moderate computing nodes. We theoretically analyze the Ergodic convergence rate of DC-Adam and compare with DC-ASGD. We implement our DC-Adam algorithm on 61 computing nodes in a computer cluster, and conduct image classification by using LeNet and ResNet, respectively, on the MNIST and CIFAR-10 datasets. The experimental results demonstrate that DC-Adam greatly accelerates the training progress and achieves almost linear speedup rate as increasing the computing nodes.

关键词： asynchronous algorithm stochastic gradient descent deep neural networks Adam delay compensation

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