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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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Using redundant threads for fault tolerance of OpenMP programs

Using redundant threads for fault tolerance of OpenMP progra...

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2010 International Conference in Information Science and Applications, ICISA 2010

作者： Fu, Hongyi Ding, Yan Key Laboratory of Science and Technology for National Defence of Parallel and Distributed Processing National University of Defence Tech. Changsha Hunan 410073 China School of Computer National University of Defence Tech. Changsha Hunan 410073 China

ISBN: (纸本)9781424459438

As the wide application of multi-core processor architecture in the domain of high performance computing, fault tolerance for shared memory parallel programs becomes a hot spot of research. For years, checkpointing has been the dominant fault tolerance technology in this field, and recently, many research works have been engaged with it. However, to those programs which deal with large amount of data, checkpointing may induce massive I/O transfer, which will adversely affect scalability. To deal with such a problem, this paper proposes a fault tolerance approach, making use of redundancy, for shared memory parallel programs. Our scheme avoids saving and restoring computational state during the program's execution, hence does not involve I/O operations, so presents explicit advantage over checkpointing in scalability. In this paper, we introduce our approach and the related compiler tool in detail, and give the experimental evaluation result. ©2010 IEEE.

关键词： Fault tolerance

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Routing with uncertainty in wireless mesh networks

Routing with uncertainty in wireless mesh networks

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2010 IEEE 18th International Workshop on Quality of Service, IWQoS 2010

作者： Chen, Fajun Liu, Jiangchuan Li, Zongpeng Wang, Yijie Key Laboratory of Science and Technology for National Defence of Parallel and Distributed Processing School of Computer National University of Defense Technology China School of Computing Science Simon Fraser University Canada Department of Computer Science University of Caglary Canada

ISBN: (纸本)9781424459889

Existing routing protocols for Wireless Mesh Networks (WMNs) are generally optimized with statistical link measures, while not addressing on the intrinsic uncertainty of wireless links. We show evidence that, with the transient link uncertainties at PHY and MAC layers, a pseudo-deterministic routing protocol that relies on average or historic statistics can hardly explore the full potentials of a multi-hop wireless mesh. We study optimal WMN routing using probing-based online anypath forwarding, with explicit consideration of transient link uncertainties. We show the underlying connection between WMN routing and the classic Canadian Traveller Problem (CTP) [1]. Inspired by a stochastic recoverable version of CTP (SRCTP), we develop a practical SRCTP-based online routing algorithm under link uncertainties. We study how dynamic next hop selection can be done with low cost, and derive a systematic selection order for minimizing transmission delay. We conduct simulation studies to verify the effectiveness of the SRCTP algorithms under diverse network configurations. In particular, compared to deterministic routing, reduction of end-to-end delay (51:15∼73:02%) and improvement on packet delivery ratio (99:76%) are observed.

关键词： Routing protocols

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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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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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SemanticCast: Content-Based Data Distribution over Self-Organizing Semantic Overlay Networks

SemanticCast: Content-Based Data Distribution over Self-Orga...

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IEEE International Conference on parallel and distributed Computing, Applications and Technologies (PDCAT)

作者： Zhong Zheng Yijie Wang National Key Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha China

Many applications demand distributing data with different contents efficiently in the network environment with unreliable links and a high node churn. Existing approaches mostly focus on optimizing either efficiency or robustness of data distribution, and fail to ensure both of them simultaneously. In this paper, we propose Semantic Cast - a content-based data distribution approach over self-organizing semantic overlay networks. Semantic Cast maintains a self-organizing semantic overlay based on view exchange (called Crowd). In Crowd, each node seeks neighbors with more similar interests by periodically exchanging its neighbor list (called view) with a chosen neighbor. Through these nodes' self-organizing behavior, various interest communities emerge in the overlay. For data distribution over Crowd, Semantic Cast adopts random walk to route data between interest communities, and adopts flooding to disseminate data inside the interested communities. The experimental results show that compared to existing approaches, Semantic Cast can support efficient content-based data distribution in the unreliable and highly dynamic network environment.

关键词： Semantics Peer to peer computing Communities Routing Robustness Convergence Subscriptions

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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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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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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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