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Scalable unbiased sampling method based on multi-peer adaptive random walk

Ruan Jian Xue Bao/Journal of Software 2009年第3期20卷 630-643页

作者： Fu, Yong-Quan Wang, Yi-Jie Zhou, Jing National Key Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha 410073 China Staff Room of Computer Command Academy of the Corps of Engineers Xuzhou 221000 China

To deal with the scalable and fast unbiased sampling problems in unstructured P2P systems, a sampling method based on multi-peer adaptive random walk (SMARW) is proposed. In the method, based on the multi-peer random walk process, a set of provisional peers are selected as agents which start the sampling processes, by which the sampling process is speeded up with receiving a set of tunable number samples each time;Meanwhile, after receiving new samples earlier agents are replaced with these new samples which repeat the sampling process. With this simple replacement, it can be guaranteed with high probability that the system can reach the optimal load balance;furthermore, SMARW adopts an adaptive distributed random walk adjustment process to increase the convergence rate of the sampling process. A detailed theorical analysis and performance evaluation confirm that SMARW has a high level of unbiased sampling and near-optimal load balancing capability. © by Institute of Software, the Chinese Academy of Sciences. All rights reserved.

关键词： Peer to peer networks

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An example-based decoder for spoken language machine translation 6

An example-based decoder for spoken language machine transla...

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6th SIGHAN Workshop on Chinese Language processing, SIGHAN 2008

作者： Li, Zhou-Jun Chao, Wen-Han Chen, Yue-Xin National Laboratory for Parallel and Distributed Processing Changsha China School of Computer Science and Engineering Beihang University China

In this paper, we propose an example-based decoder for a statistical machine translation (SMT) system, which is used for spoken language machine translation. In this way, it will help to solve the re-ordering problem and other problems for spoken language MT, such as lots of omissions, idioms etc. Through experiments, we show that this approach obtains improvements over the baseline on a Chinese-English spoken language translation task. © IJCNLP 2008. All rights reserved.

关键词： Machine translation

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Automating software FMEA via formal analysis of dependence relations

Automating software FMEA via formal analysis of dependence r...

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32nd Annual IEEE International computer Software and Applications Conference, COMPSAC 2008

作者： Dong, Wei Wang, Ji Zhao, Changzhi Zhang, Xian Tian, Jie School of Computer National University of Defense Technology China National Laboratory for Parallel and Distributed Processing China

ISBN: (纸本)9780769532622

The paper presents the ongoing work of studying FMEA method for embedded safety critical software via formal analysis of various dependence relations among software elements, which can fairly improve the automation and precision of both system level and detailed level FMEA. These dependence relations are depicted by the formal models abstracted from software design and implementation, and the FMEA processes for both structural and object-oriented software are proposed respectively. The initial result of case study shows the effectiveness of the approach. I 2008 IEEE.

关键词： Safety engineering

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A distributed topology-aware overlays construction algorithm 08

A distributed topology-aware overlays construction algorithm

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15th ACM Mardi Gras Conference, MG '08

作者： Zhang, Xiaoming Li, Zhoujun Wang, Yijie School of Computer Science and Engineering Beihang University Beijing 100083 China National Laboratory for Parallel and Distributed Processing NUDT Changsha 410073 China

ISBN: (纸本)9781595938350

Peer-to-Peer (P2P) computing systems are rapidly growing in importance as the medium of choice for the mass storage. Peers in the most P2P systems randomly choose logical neighbors without any knowledge about underlying physical topology. This mechanism can cause a serious topology mismatch between the P2P overlay network and the underlying network. It greatly limits the performance gain from various search or routing techniques. In this paper, a distributed topology-aware overlays construction algorithm Taonet is proposed, in which the overlay network construction is based on the location information of underlying topology. The nodes that are close in the logical network are also close in terms of network latency. This leads to low latency stretch of the overlay network. This algorithm is scalable and distributed. Simulation results indicate that the latency of data location in these topology-aware P2P systems that are constructed with Taonet can be significantly decreased. Copyright © 2008 ACM.

关键词： Overlay networks

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Effective runtime scalability metric to measure productivity in high performance computing systems 08

Effective runtime scalability metric to measure productivity...

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2008 Conference on Computing Frontiers, CF'08

作者： Du, Jing Yang, Xuejun Wang, Zhiyuan National Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha Hunan 410073 China

ISBN: (纸本)9781605580777

Current high performance computing systems all rely on parallel processing techniques to achieve high performance. With the parallel computer systems scaling up, the new generation of high performance computers puts more emphasis on "high productivity" [1], rather than "high performance" as in the past. These new systems will not only meet the traditional requirements of computing performance, but also address the ongoing technical challenges in the current high-end computing domain regarding energy consumption, reliability, etc. For energy consumption, with the computer system scaling up, it increases dramatically [2]. High energy consumption means high maintenance cost and low system stability. For example, the peak energy consumption of the Earth Simulator and BlueGene/L is 18MW and 1.6MW respectively. For reliability, with the complexity of a computer system increasing, its meantimebetween-failure (MTBF) is becoming significantly shorter than what is required by many current high performance computing applications [3], such as BlueGene/L. Therefore, energy optimization techniques and fault tolerance techniques should be introduced to computer systems to achieve low energy consumption and high reliability. To improve the productivity of high performance computing systems, we need to find a proper way to measure it. Unfortunately, traditional measurement models can not evaluate the system productivity comprehensively and effectively [4]. To address this issue, this paper proposes an effective scalability metric for high performance computing systems based on Gustafson speedup law. The metric makes a good balance among runtime productivity factors including computing performance, energy consumption and reliability. The contribution of our work lies in the following three aspects. First, in order to measure the scalability of an energyconsumption optimized parallel program, we should consider not only whether the program computing performance is scalable, but also w

关键词： Energy utilization

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Optimistic data consistency maintenance method based on data dependence

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Jisuanji Xuebao/Chinese Journal of computers 2008年第5期31卷 741-753页

作者： Zhou, Jing Wang, Yi-Jie Li, Si-Kun National Key Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha 410073 China

This paper proposes an optimistic data consistency method according to the question about data dependence in data consistency. In the method, data object is partitioned into data blocks by fixed size as the basic unit of data management. Updates are compressed by Bloom filter technique and propagated in double-path. Negotiation algorithms detect and reconcile update conflicts, and dynamic data management algorithms accommodate dynamic data processing. The results of the performance evaluation show that it is an efficient method to achieve consistency, good dynamic property, and strong robustness when choosing the size of data block appropriately. At the same time, a feasible way is put forward on how to choose appropriate data block size.

关键词： Data processing

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Optimistic data consistency maintenance method based on key-attributes

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Ruan Jian Xue Bao/Journal of Software 2008年第8期19卷 2114-2126页

作者： Zhou, Jing Wang, Yi-Jie Li, Si-Kun National Key Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha 410073 China

The features of simple description, small updates item and weak dependence are the main characteristics of updates of key-attributes in P2P systems. Accordingly, an optimistic data consistency maintenance method based on key-attributes is proposed. In the method, the update of key-attributes is separated from user update requests. Key-Updates are propagated by latency-overlay update propagation model, that is, updates are always propagated to the nodes having maximum or minimum latency, and assured and uncertain propagation paths of updates are all taken into account. Based on classifying key-update conflicts, a double-level reconciling mechanism including buffer preprocessing and update-log processing is applied to detect and reconcile conflicts, and then conflicts are solved by policies as last-writer-win and divide-and-rule. Lastly, update-log management method and maintenance method brought by node failure and network partitioning are discussed for the above is deployed based on the information storied in update-log. Delaying key-attributes updates cannot occur by the optimistic disposal method, and then it cannot depress efficiency of resource location based on key-attributes, which adapts well to P2P systems for Internet. The simulation results show that it is an effective optimistic data consistency maintenance method, achieving good consistency overhead, resource location and resource access overhead, and having strong robustness.

关键词： Maintenance

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Symbolic Model Checking APSL

Symbolic Model Checking APSL

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第二届IFIP/IEEE软件工程理论基础国际研讨会(TASE 2008)(Second IFIP/IEEE International Symposium on Theoretical Aspects of Software engineering)

作者： Wanwei Liu Ji Wang Huowang Chen Xiaodong Ma National Laboratory for Parallel and Distributed Processing School of computer National University of Defense Technology China

PSL is a kind of temporal logic which uses SEREs as additional formula constructs. We present a variant of PSL, namely APSL, which replaces SEREs with finite automata. APSL and PSL are of the exactly same expressiveness. In this paper, we extend the LTL symbolic model checking algorithm to that of APSL, and present a tableau based APSL verification approach. Moreover, we show how to implement this algorithm via the BDD based symbolic approach.

关键词： Automata Logic Data structures Boolean functions Binary decision diagrams Software engineering Laboratories distributed processing Concurrent computing distributed computing

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Analyzing the Efficiency and Bottleneck of Scientific Programs on Imagine Stream Processor by Simulation

Analyzing the Efficiency and Bottleneck of Scientific Progra...

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International Symposium on parallel and distributed processing with Applications, ISPA

作者： Yonggang Che Chuanfu Xu Zhenghua Wang National Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha China

Imagine stream processor has shown high performance and efficiency for media applications. Its potential for scientific applications is of great interest to the high performance computing community. This paper investigates this subject from a new angle. It roughly classifies the scientific programs into three classes based on their computation to memory access ratios. For each class, typical programs are programmed with StreamC/KernelC stream language and simulated based on the cycle-accurate simulator of Imagine. In-depth analysis is carried out for the performance data, with special attentions on the performance bottlenecks. The performance data obtained on Imagine are compared against data on two general-purpose x86 processors. The results show that programs with no DRAM accesses attain high floating point performance and efficiencies on Imagine. These programs' performance is only restricted by limited ILP (Instruction-Level parallelism) and load imbalance across ALUs. Programs with computation to memory operation ratios O(n) attain absolute floating point performance on Imagine comparable to that obtained on general-purpose processors, but their floating-point efficiencies are not satisfactory. It is essential to optimize these programs for high SRF (Stream Register File) and LRF (Local Register File) reuse and high ILP on Imagine. Programs with lower computation to memory operation ratios attain much lower floating-point performance and efficiencies on Imagine, compared to those obtained on x86 processors.

关键词： Image analysis Streaming media Analytical models computer architecture Computational modeling High performance computing Bandwidth Arithmetic Application software Scientific computing

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Automating Software FMEA via Formal Analysis of Dependence Relations

Automating Software FMEA via Formal Analysis of Dependence R...

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IEEE Annual International computer Software and Applications Conference (COMPSAC)

作者： Wei Dong Ji Wang Changzhi Zhao Xian Zhang Jie Tian School of Computer National University of Defense Technology China National Laboratory for Parallel and Distributed Processing China

The paper presents the ongoing work of studying FMEA method for embedded safely critical software via formal analysis of various dependence relations among software elements, which can fairly improve the automation and precision of both system level and detailed level FMEA. These dependence relations are depicted by the formal models abstracted from software design and implementation, and the FMEA processes for both structural and object-oriented software are proposed respectively. The initial result of case study shows the effectiveness of the approach.

关键词： Software Unified modeling language Safety Aircraft Object oriented modeling Atmospheric modeling Software reliability

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