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Jacobi-Sobolev Orthogonal Polynomialsand Spectral Methods for Elliptic Boundary Value Problems

Communications on Applied Mathematics and Computation 2019年第2期1卷 283-308页

作者： Xuhong Yu Zhongqing Wang Huiyuan Li University of Shanghai for Science and Technology Shanghai 200093China State Key Laboratory of Computer Science/Laboratory of Parallel Computing Institute of SoftwareChinese Academy of SciencesBeijing 100190China

Generalized Jacobi polynomials with indexes α,β∈ R are introduced and some basic properties are established. As examples of applications,the second- and fourth-order elliptic boundary value problems with Dirichlet or Robin boundary conditions are considered,and the generalized Jacobi spectral schemes are proposed. For the diagonalization of discrete systems,the Jacobi-Sobolev orthogonal basis functions are constructed,which allow the exact solutions and the approximate solutions to be represented in the forms of infinite and truncated Jacobi series. Error estimates are obtained and numerical results are provided to illustrate the effectiveness and the spectral accuracy.

关键词： Generalized Jacobi polynomials Spectral method - Jacobi-Sobolev orthogonal basis functions Elliptic boundary value problems Error analysis

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Improving accuracy and coverage in an internet-deployed reputation mechanism

Improving accuracy and coverage in an internet-deployed repu...

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2010 IEEE 10th International Conference on Peer-to-Peer Computing, P2P 2010

作者： Delaviz, Rahim Andrade, Nazareno Pouwelse, Johan A. Parallel and Distributed Systems Group Department of Computer Science Delft University of Technology Netherlands

ISBN: (纸本)9781424471416

P2P systems can benefit from reputation mechanisms to promote cooperation and help peers to identify good service providers. However, in spite of a large number of proposed reputation mechanisms, few have been investigated in real situations. BarterCast is a distributed reputation mechanism used by our Internet-deployed Bittorent-based file-sharing client Tribler. In BarterCast, each peer uses messages received from other peers to build a weighted, directed subjective graph that represents the upload and download activity in the system. A peer calculates the reputations of other peers by applying the maxflow algorithm to its subjective graph. For efficiency reasons, only paths of at most two hops are considered in this calculation. In this paper, we identify and assess three potential modifications to BarterCast for improving its accuracy and coverage (fraction of peers for which a reputation value can be computed). First, a peer executes maxflow from the perspective of the node with the highest betweenness centrality in its subjective graph instead of itself. Second, we assume a gossiping protocol that gives each peer complete information about upload and download activities in the system, and third, we lift the path length restriction in the maxflow algorithm. To assess these modifications, we crawl the Tribler network and collect the upload and download actions of the peers for three months. We apply BarterCast with and without the modifications on the collected data and measure accuracy and coverage. ©2010 IEEE.

关键词： Peer to peer networks

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Large-scale virtual machines provisioning in clouds： challenges and approaches

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Frontiers of Computer science 2016年第1期10卷 2-18页

作者： Zhaoning ZHANG Dongsheng LI Kui WU National Laboratory for Parallel and Distributed Processing School of Computer Science National University of Defense Technology Changsha 410073 China Computer Science Department University of Victoria Victoria V8W 2Y2 Canada

The scale of global data center market has been explosive in recent years. As the market grows, the demand for fast provisioning of the virtual resources to support elas- tic, manageable, and economical computing over the cloud becomes high. Fast provisioning of large-scale virtual ma- chines （VMs）, in particular, is critical to guarantee quality of service （QoS）. In this paper, we systematically review the existing VM provisioning schemes and classify them in three main categories. We discuss the features and research status of each category, and introduce two recent solutions, VMThunder and VMThunder＋, both of which can provision hundreds of VMs in seconds.

关键词： cloud computing IaaS large scale virtual ma-chine provisioning

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Constructing neighbor-joining phylogenetic trees with reduced redundancy computation

Constructing neighbor-joining phylogenetic trees with reduce...

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12th IEEE International Conference on Electronics, Circuits and Systems, ICECS 2005

作者： Chen, Ningtao Shi, Baochang Wang, Nengchao School of Computer Science and Technology Huazhong University of Science and Technology Wuhan 430074 China Parallel Computing Institute Huazhong University of Science and Technology Wuhan 430074 China

ISBN: (纸本)9789972611001

A fast algorithm for constructing Neighbor-Joining phylogenetic trees has been developed. The CPU time is drastically reduced as compared with Saitou and Nei's algorithm (SN) [4] and Studier and Kepler's algorithm (SK) [5]. The new algorithm includes three techniques: Firstly, a linear array A[N] is introduced to store the sum of every row of the distance matrix (the same as SK), which can eliminate many repeated (redundancy) computations. Secondly, the value of A[i] are computed only once at the beginning of the algorithm, and are updated by three elements in the iteration. Thirdly, a very compact formula for the sum of all the branch lengths of OTUs (Operational Taxonomic Units) i and j has been designed. The results show that our algorithm is from tens to hundreds times faster than SN and about two times faster than SK when N increases, constructing the tree with 2000 OTUs in 3 minutes on our desktop computer (CPU: Intel Celeron 2.4GHz, RAM: 256MB and OS: Windows 2000 Professional).

关键词： Trees (mathematics)

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A clustering-based approach for mining dockerfile evolutionary trajectories

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science China(Information sciences) 2019年第1期62卷 211-213页

作者： Yang ZHANG Huaimin WANG Vladimir FILKOV Key Laboratory of Parallel and Distributed Computing National University of Defense Technology College of Computer National University of Defense Technology DECAL Lab University of California Computer Science Department University of California

Dear editor,Docker1), as a de-facto industry standard [1], enables the packaging of an application with all its dependencies and execution environment in a light-weight, self-contained unit, i.e., *** launching the container from Docker image, developers can easily share the same operating system, libraries, and binaries [2]. As the configuration file, the dockerfile plays an important role,

关键词： A clustering-based approach for mining dockerfile evolutionary trajectories

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BitTorrent's dilemma: Enhancing reciprocity or reducing inequity

BitTorrent's dilemma: Enhancing reciprocity or reducing ineq...

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2011 IEEE Consumer Communications and Networking Conference, CCNC'2011

作者： Jia, Adele L. D'Acunto, Lucia Meulpolder, Michel Pouwelse, Johan A. Epema, Dick H. J. Parallel and Distributed Systems Group Department of Computer Science Delft University of Technology Netherlands

ISBN: (纸本)9781424487905

Enhancing reciprocity has been one of the primary motivations for the design of incentive policies in BitTorrent-like P2P systems. Reciprocity implies that peers need to contribute their bandwidth to other peers if they want to receive bandwidth in return. However, the over-provisioning that characterizes today's BitTorrent communities and the development of many next-generation P2P systems with real-time constraints (e.g., for live and on-demand streaming) suggest that more effort can be devoted to reducing the inequity (i.e., the difference of service received) among peers, rather than only enhancing reciprocity. Inspired by this observation, in this work we analyze in detail several incentive mechanisms that are used in BitTorrent systems, and explore several strategies that influence the balance between reciprocity and equity. Our study shows that (i) reducing inequity leads to a better overall system performance, and (ii) the behavior of seeders (i.e., peers that hold a complete copy of the file and upload it for free) influences whether reciprocity is enhanced or inequity reduced. © 2011 IEEE.

关键词： Bandwidth

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Collaborative search in large-scale unstructured peer-to-peer networks

Collaborative search in large-scale unstructured peer-to-pee...

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36th International Conference on parallel Processing in Xi'an, ICPP

作者： Zhang, Yiming Li, Dongsheng Chen, Lei Lu, Xicheng National Laboratory for Parallel and Distributed Processing NUDT Department of Computer Science Hong Kong University of Science and Technology

ISBN: (纸本)076952933X

Searching in large-scale unstructured peer-to-peer networks is challenging due to the lack of effective hint information to guide queries. In this paper, we propose POP, a parallel, cOllaborative and Probabilistic search mechanism, in which query messages are viewed as search units to collaborate with each other and aggregate the distributed hints during the search process. A scheme called Distributed Bloom Filter (DBF) is presented to propagate the hints with a bandwidth-aware manner, in which a node divides the received Bloom filter vector into subvectors and disseminates the fragments to its neighbors according to their bandwidth capacity. The effectiveness of POP is demonstrated through theoretical analysis and extensive simulations. © 2007 IEEE.

关键词： Bandwidth

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The evolving generation and fast algorithms of walsh transforms

The evolving generation and fast algorithms of walsh transfo...

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12th IEEE International Conference on Electronics, Circuits and Systems, ICECS 2005

作者： Chen, Ningtao Wang, Nengchao Shi, Baochang School of Computer Science and Technology Huazhong University of Science and Technology Wuhan 430074 China Parallel Computing Institute Huazhong University of Science and Technology Wuhan 430074 China

ISBN: (纸本)9789972611001

Six orderings of Walsh function are derived evolutionally by means of "row copy" and "block copy". Two (Walsh-and Paley-ordering) are generated by row copy and other four (Hadamard-, X-, XT- and G-ordering) are generated by block copy. XT- and G-ordering are deduced by extending the concept of up-down shift symmetry to that of up-down mirror image symmetry. XT-ordering is the transposed X-ordering, which is not symmetric as X-ordering;G-ordering is symmetric as the three known ones (Walsh- and Paley- and Hadamard-ordering). The four symmetric orderings construct an exactly symmetric Walsh function system. At last, two fast algorithms are proposed for G-ordering Walsh transform. The approaches introduced are applicable to other orderings Walsh transforms. Both algorithms have a regular recursive structure and are easy to be implemented on parallel computers. Furthermore, the method serves as a frame to design fast algorithms for discrete transforms.

关键词： Walsh transforms

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Distributed Aggregation Algorithms for Mobile Sensor Networks with Group Mobility Model

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Tsinghua science and technology 2012年第5期17卷 512-520页

作者： Qianqian Ren Longjiang Guo Jinghua Zhu Meirui Ren Junqing Zhu School of Computer Science and Technology Heilongjiang UniversityHarbin 150080China Key Laboratory of Database and Parallel Computing of Heilongjiang Province Harbin 150080China

In many applications of mobile sensor networks, such as water flow monitoring and disaster rescue, the nodes in the network can move together or separate temporarily. The dynamic network topology makes traditional spanning-tree-based aggregation algorithms invalid in mobile sensor networks. In this paper, we first present a distributed clustering algorithm which divides mobile sensor nodes into several groups, and then propose two distributed aggregation algorithms, Distance-AGG （Aggregation based on Distance）, and Probability-AGG （Aggregation based on Probability）. Both of these two algorithms conduct an aggregation query in three phases： query dissemination, intra-group aggregation, and inter-group aggregation. These two algorithms are efficient especially in mobile networks. We evaluate the performance of the proposed algorithms in terms of aggregation accuracy, energy efficiency, and query delay through ns-2 simulations. The results show that Distance-AGG and Probability-AGG can obtain higher accuracy with lower transmission and query delay than the existing aggregation algorithms.

关键词： mobile sensor networks data aggregation group mobility model distributed algorithms

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Labelwalking nonnegative matrix factorization 40

Labelwalking nonnegative matrix factorization

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40th IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP 2015

作者： Lan, Long Guan, Naiyang Zhang, Xiang Huang, Xuhui Luo, Zhigang Science and Technology on Parallel and Distributed Processing Laboratory College of Computer National University of Defense Technology Changsha China

ISBN: (纸本)9781467369978

Semi-supervised learning (SSL) utilizes plenty of unlabeled examples to boost the performance of learning from limited labeled examples. Due to its great discriminant power, SSL has been widely applied to various real-world tasks such as information retrieval, pattern recognition, and speech separa- tion. Label propagation (LP) is a popular SSL method which propagates labels through the dataset along high density areas defined by unlabeled examples, LP assumes nearby examples should share the same label, thus, it unavoidably pushes the labels to the wrong examples, especially when different la- beled examples are not strictly separated. Seed K-means uses labeled examples to initialize class centers, and avoid getting stuck in poor local optima comparing to traditional K-means, however the hard constraint of each example's membership makes Seed K-means failed in many real world applications. This paper proposes a novel label walking nonnegative matrix factorization method (LWNMF) to handle labeled examples in SSL based on the framework of NMF. LWNMF decomposes the whole dataset into the product of a basis matrix and a coefficient matrix, and to travel labels to unlabeled examples, LWNMF regards the class indicators of labeled examples as their coefficients and iteratively updates both basis matrix and coefficients of unlabeled examples. Since LWNMF learns comprehensive class centroids, labels iteratively walk to unlabeled examples through these significant centroids. © 2015 IEEE.

关键词： K-means Label propagation Nonnegative matrix factorization Semisupervised learning

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