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Symposia and Workshops on Ubiquitous, Autonomic and Trusted Computing, UIC-ATC

作者： Yanrong Ding Xiaodong Wang Hu Shen Pengyu Guo National Key Laboratory for Parallel and Distributed Processing Changsha China

Nested Circular Directional MAC, a modified medium access control protocol of DMAC protocol, is proposed in this paper to support both directional antennas and omni-directional antennas simultaneously in one Ad Hoc network. Omni-directional antennas follow the RTS/CTS mechanism which is multi-hop and directional antennas follow the DRTS/DCTS mechanism, ensuring the asymmetric communication effectively. In order to resolve new deafness problem and hidden terminal problem, the directional antennas also use circular DRTS and nested antenna circumrotation. Simulation results show that NCDMAC supports hybrid antennas effectively and is better than MMAC and Circular-MAC in terms of increasing throughput, but it also increases the communication delay.

关键词： Delay Deafness Directive antennas Throughput Directional antennas Media Access Protocol

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A load balancing-supported constant degree DHT ID assignment method

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Tien Tzu Hsueh Pao/Acta Electronica Sinica 2010年第11期38卷 2649-2654页

作者： Wang, Xiao-Hai Peng, Yu-Xing Li, Dong-Sheng Key Laboratory of Science and Technology for Parallel and Distributed Processing National University of Defense Technology Changsha Hunan 410073 China

A Load Balancing-Supported ID assignment method is the foundation to implement and maintain DHT overlays, realized constant degree DHTs usually use simple pure centralized or distributed ID management strategies, which cannot resolve the contradiction between cost of maintaining topologies' information and topologies' balance. Analyzing the universal tree structures in the topologies, an ID Assignment method RFIDAM based on the internal structure Routing Forest is proposed, which regularly aggregates local balancing information to guide new nodes' joining for overall balance. The experimental results show, with low maintenance and routing message overhead, the system's loading balance is efficiently ensured with the length of IDs differ by at most 2.

关键词： Topology

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The composability problem of events and threads in distributed systems

ICETC 2010 - 2010 2nd International Conference on Education ...

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ICETC 2010 - 2010 2nd International Conference on Education Technology and Computer 2010年 4卷 V4311-V4315页

作者： Li, Huiba Peng, Yuxing Lu, Xicheng National Laboratory for Parallel and Distributed Processing National University of Defense Technology Changsha 410073 China

ISBN: (纸本)9781424463688

Event-driven programming has been a relatively hot topic in distributed systems development. Having worked on these systems for years, we now believe that it is not the best choice. Besides the well-known "stack ripping" problem, we argue that it greatly influences the composability of software modules. Preemptive threads are also short of composability because of data-races and locks. Lacking of composability can result in systems with little vitality. Cooperative threading (or coroutine), on the contrary, is almost free of this problem, so we advocate it as the primary concurrency model for most distributed systems. © 2010 IEEE.

关键词： distributed computer systems

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Simulation research of communication networks based on prim algorithm

Simulation research of communication networks based on prim ...

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International Forum on Information Technology and Applications

作者： Yang, Chenghui Ren, ChuanJun College of Electrical Engineering Northwest University for Nationalities Lanzhou 730030 China National Laboratory for Parallel and Distributed Processing College of Computer Science National University of Defense Technology Changsha 410073 China

ISBN: (纸本)9780769541150

In order to improve the efficiency of the communication networks, we used the Kruskal algorithm and the Prim algorithm through algorithm comparison and analysis methods of data structure. A dynamic framework for the communication network installed system is built. Moreover, according to the actual framework of the communication network specific issues, the module chooses the Minimum Cost Spanning Tree Prim algorithm ultimately. The assumptions process and outcomes simulation have proper analysis and certification by C language. Experimental results show that the Minimum Cost Spanning Tree of Prim algorithm on the installed system for communication networks dynamic planning process have the advantage of speed and effectively reduce the waste of resources, which not only can ensure efficiency but also can effectively improve communication networks installed cost. © 2010 IEEE.

关键词： Costs

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Two improved GPU acceleration strategies for force-directed graph layout

Two improved GPU acceleration strategies for force-directed ...

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International Conference on Computer Application and System Modeling (ICCASM)

作者： Yong-Xian Wang Zong-Zhe Li Lu Yao Wei Cao Zheng-Hua Wang National Key Laboratory of Parallel and Distributed Processing National University of Defense Technology Changsha China National Key Laboratory for Parallel and Distributed Processing National University of Defense Technology Changsha China

Force directed approach is one of the most widely used methods in graph drawing research. However, the running time is increased intolerablely along with the enlargement of the graph size, which restricts the algorithm's practicability. By the aid of GPU (graphics processing unit) computing platform, we can speed-up the graph layout with low cost, but the existing GPU implementation mainly employees an “one-by-one” style to update the vertex' coordination per iteration, which has a lower convergent rate than the “batch” style which is instead used commonly in traditional CPU implementation. As a result, the aesthetics of graph layout would be decreased if the total running time is restricted. It is hard to achieve both a high speedup factor of GPU over CPU and a high convergent rate in existing GPU computing implementation. In order to solve this problem partially, this paper presents two new strategies to implement the large-scale graph layout on CPU+GPU heteromerous platform to accelerate the force directed layout for graph drawing problem. The numerical computation results show that our GPU implementation can dramatically improve the performance of force-direct layout and is 20 times on a NVIDIA GeForce 9800 GT GPU at 1.44 GHz faster than the one on single-CPU core of Intel Pentium 4 PC at 3.0 GHz for the graph layout with moderate size (typically 1000 vertices).

关键词： Graphics processing unit Gallium nitride Heating

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Towards building efficient content-based publish/subscribe systems over structured P2P overlays

Towards building efficient content-based publish/subscribe s...

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International Conference on parallel processing

作者： Zhang, Shengdong Wang, Ji Shen, Rui Xu, Jie National Laboratory for Parallel and Distributed Processing National University of Defense Technology Changsha 410073 China School of Computing University of Leeds Leeds LS2 9JT United Kingdom

ISBN: (纸本)9780769541563

In this paper, we introduce a generic model to deal with the event matching problem of content-based publish/ subscribe systems over structured P2P overlays. In this model, we claim that there are three methods (eventoriented, subscription-oriented and hybrid) to make all the matched pairs (event, subscription) meet in a system. By theoretically analyzing the inherent problem of both eventoriented and subscription-oriented methods, we propose PEM (Popularity-based Event Matching), a variant of hybrid method. PEM can achieve better trade-off between event processing load and subscription storage load of a system. PEM has been verified through both mathematical and simulation-based evaluation. © 2010 IEEE.

关键词： Message passing

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Mapping OpenMP Concepts to the Stream Programming Model

Mapping OpenMP Concepts to the Stream Programming Model

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The 5th International Conference on Computer Science & Education(第五届国际计算机新技术与教育学术研讨会 ICCSE'10)

作者： Tao Tang Yisong Lin Xiaoguang Ren National Laboratory for Parallel and Distributed Processing National University of Defense Technology Changsha China

OpenMP is a widely used parallel programming model on traditional multi-core processors. Generally, OpenMP is used to develop fine-grained parallelism through a multithread model. Stream programming model is a new kind of parallel programming model for stream architectures. OpenMP bears a resemblance to the stream programming model at some level. The transformation between the two models has attracted much attention from the research community, since it is the foundation of porting programs between the two architectures. Most related researches focus on the efficiency of porting existing parallel programs to the new architectures such as GPUs. Very few of these studies, however, focus on the portative problem systematically, namely, what kind of parallel programs can be or should be transplanted into stream programs and mapped to run on the stream processors. In this paper, we study the mapping relationship of parallel mechanism in OpenMP to the stream programming model, and point out those parallel mechanisms in OpenMP that are infeasible or undesirable for stream programs. By analyzing two typical benchmarks, we draw the conclusion that a majority of scientific applications are suitable to be mapped to the stream programming model. Our conclusion effectively validates the idea of accelerating scientific applications with the stream processors.

关键词： OpenMP:stream programming model:parallel mechanism:mapping

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Nexus: Speculative Execution for Event-Driven Networking Programs

Nexus: Speculative Execution for Event-Driven Networking Pro...

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International Conference on parallel and distributed Systems (ICPADS)

作者： Huiba Li Xicheng Lu Yuxing Peng National Laboratory of Parallel and Distributed Processing National University of Defense Technology Changsha China

The efficiency of communication is a key factor to the performance of networking applications, and concurrent communication is an important approach to the efficiency of communication. However, many concurrency opportunities are very difficult to exploit because they depend on some undeterministic conditions. If these conditions are highly predictable, speculative execution can be a very effective approach to cope with the uncertainties. Existing researches on speculation seldom target at networking systems, and none of them can handle the event-driven model that is very popular in such systems. In this paper, we propose Nexus, a novel speculation scheme that supports event-driven networking applications. Nexus analyzes the dependence relationship of events, and performs speculation according to the duality of events and threads. Evaluation on a prototype implementation of nexus shows that this approach can significantly reduces the time needed to complete an event-driven program.

关键词： Containers Internet Prototypes Instruction sets Benchmark testing Protocols Programming

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Automatic Concurrency Management for distributed applications

Automatic Concurrency Management for distributed application...

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IEEE Symposium on Computers and Communications (ISCC)

作者： Huiba Li Shengyun Liu Yuxing Peng Dongsheng Li National Laboratory for Parallel and Distributed Processing National University of Defense Technology Changsha China

ISBN: (纸本)9781424477548;9781424477555

Building distributed applications is difficult mostly because of concurrency management. Existing approaches primarily include events and threads. Researchers and developers have been debating for decades to prove which is superior. Although the conclusion is far from obvious, this long debate clearly shows that neither of them is perfect. One of the problems is that they are both complex and error-prone. Both events and threads need the programmers to explicitly manage concurrency, and we believe it is just the source of difficulties. In this paper, we propose a novel approach-automatic concurrency management by the runtime system. It dynamically analyzes the programs to discover potential concurrency opportunities; and it dynamically schedules the communication and the computation tasks, resulting in automatic concurrent execution. This approach is inspired by the instruction scheduling technologies used in modern microprocessors, which dynamically exploits instruction-level parallelism. However, hardware scheduling algorithms do not fit software in many aspects, thus we have to design a new scheme completely from scratch. automatic concurrency management is a runtime technique with no modification to the language, compiler or byte code, so it is good at backward compatibility. It is essentially a dynamic optimization for networking programs.

关键词： Concurrent computing Dynamic scheduling Semantics Out of order Runtime Virtual machining

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Personalized reputation model in cooperative distributed systems

Personalized reputation model in cooperative distributed sys...

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16th IEEE International Conference on parallel and distributed Systems, ICPADS 2010

作者： Liu, Wei Tang, Yang-Bin Wang, Huai-Min School of Computer National Univ. of Defense Technology Changsha Hunan China Institute of Science National Univ. of Defense Technology Changsha Hunan China National Laboratory for Parallel and Distributed Processing Changsha Hunan China

ISBN: (纸本)9780769543079

Reputation systems provide a promising way to build trust relationships between users in distributed cooperation systems, such as file sharing, streaming, distributed computing and social network, through which a user can distinguish good services or users from malicious ones and cooperate with them. However, most reputation models mainly focus on evaluating the quality of services in one dimension, but care less about the preferences of different users. This paper proposes a personalized reputation model which provides each user a personalized trust view on others according to his preferences. In our approach, we aggregate the users' preferences with collaborative filtering method and qualify it with user similarity which is integrated into the computing of reputation value. The experimental results suggest that our model can resist possible kinds of malicious behaviors efficiently. © 2010 IEEE.

关键词： distributed computer systems

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