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Embedded DHT overlays in virtual computing environments

Science China(Information Sciences) 2010年第3期53卷 483-493页

作者： ZHANG YiMing, LU XiCheng & LI DongSheng 1.0} {1.oratory for parallel and distributed processing (PDL), Changsha 41.073, China 2School of Computer, national University of Defense Technology, Changsha 41.073, China 1. National Laboratory for Parallel and Distributed Processing (PDL) Changsha 410073 China

With the rapid development of computing and networking technologies, people propose to build harmonious, trusted and transparent Internet-based virtual computing environments (iVCE). The overlay-based organization of dynamic Internet resources is an important approach for iVCE to realizing efficient resource sharing. DHT-based overlays are scalable, low-latency and highly available; however, the current DHT overlay (SKY) in iVCE cannot satisfy the "trust" requirements of Internet applications. To address this problem, in this paper we modify SKY and propose TrustedSKY, an embedded DHT overlay technique in iVCE which supports applications to select trusted nodes to form a "trusted subgroup" in the base overlay and realize secure and trusted DHT routing.

关键词： Internet-based virtual computing environment (iVCE) DHT overlay TrustedSKY

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SCautz:a high performance and fault-tolerant datacenter network for modular datacenters

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Science China(Information Sciences) 2012年第7期55卷 1493-1508页

作者： HUANG Feng,LU XiCheng,LI DongSheng & ZHANG YiMing national {1. for parallel and distributed processing,School of Computer,national University of Defense Technology,Changsha 41.073,China 1. National Lab for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha 410073 China

Modular datacenters (MDCs) use shipping containers,encapsulating thousands of servers,as large pluggable building blocks for mega *** MDC’s "service-free" model poses stricter demand on fault-tolerance of the modular datacenter network (MDCN).Based on the "scale-out" principle,in this paper we propose SCautz,a novel hybrid intra-container network for *** comprises a base Kautz topology,created by interconnecting servers,and a small number of COTS (commercial off-the-shelf) ***,each switch connects a specific number of servers forming "clusters",which,as logical nodes,form multiple higher-level logical Kautz ***’s hybrid structure has several ***,it supports multiple running modes for the MDC,while its full structure increases network capacity ***,it retains the throughput for processing one-to-x traffic in the presence of ***,it achieves much more graceful network performance degradation than computation and storage capacity *** from theoretical analysis and simulations show that SCautz is more viable for intra-container networks.

关键词： modular datacenter network container Kautz fault-tolerant

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Superscalar communication: A runtime optimization for distributed applications

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Science China(Information Sciences) 2010年第10期53卷 1931-1946页

作者： LI HuiBa , LIU ShengYun, PENG YuXing, LI DongSheng, ZHOU HangJun & LU XiCheng national {1.oratory for parallel and distributed processing, national University of Defense Technology, Changsha 41.073, China 1. National Laboratory for Parallel and Distributed Processing National University of Defense Technology Changsha 410073 China

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 concurrencies, and we believe it is just the source of difficulties. In this paper, we propose a novel approach—superscalar communication, in which concurrencies are automatically managed 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 idea of superscalar technology in modern microprocessors, which dynamically exploits instruction-level {1.ism. However, hardware superscalar algorithms do not fit software in many aspects, thus we have to design a new scheme completely from scratch. Superscalar communication is a runtime extension with no modification to the language, compiler or byte code, so it is good at backward compatibility. Superscalar communication is likely to begin a brand new research area in systems software, which is characterized by dynamic optimization for networking programs.

关键词： network programming concurrency event thread superscalar

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MPtostream:an OpenMP compiler for CPU-GPU heterogeneous parallel systems

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Science China(Information Sciences) 2012年第9期55卷 1961-1971页

作者： YANG XueJun,TANG Tao ,WANG GuiBin,JIA Jia & XU XinHai national {1.oratory for parallel and distributed processing,national University of Defense Technology,Changsha 41.073,China 1. National Laboratory for Parallel and Distributed Processing National University of Defense Technology Changsha 410073 China

In light of GPUs’ powerful floating-point operation capacity,heterogeneous parallel systems incorporating general purpose CPUs and GPUs have become a highlight in the research field of high performance computing(HPC).However,due to the complexity of programming on GPUs,porting a large number of existing scientific computing applications to the heterogeneous parallel systems remains a big *** OpenMP programming interface is widely adopted on multi-core CPUs in the field of scientific *** effectively inherit existing OpenMP applications and reduce the transplant cost,we extend OpenMP with a group of compiler directives,which explicitly divide tasks among the CPU and the GPU,and map time-consuming computing fragments to run on the GPU,thus dramatically simplifying the *** have designed and implemented MPtoStream,a compiler of the extended OpenMP for AMD’s stream processing *** experimental results show that programming with the extended directives deviates from programming with OpenMP by less than 1.% modification and achieves significant speedup ranging from 3.1.to 1..3 on a heterogeneous system,incorporating an Intel Xeon E5405 CPU and an AMD FireStream 9250 GPU,over the execution on the Xeon CPU alone.

关键词： GPGPU stream OpenMP compiler

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A fast successive over-relaxation algorithm for force-directed network graph drawing

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Science China(Information Sciences) 2012年第3期55卷 677-688页

作者： WANG YongXian & WANG ZhengHua national Key {1.oratory for parallel and distributed processing, national University of Defense Technology, Changsha 41.073, China 1. National Key Laboratory for Parallel and Distributed Processing National University of Defense Technology Changsha 410073 China

Force-directed approach is one of the most widely used methods in graph drawing research. There are two main problems with the traditional force-directed algorithms. First, there is no mature theory to ensure the convergence of iteration sequence used in the algorithm and further, it is hard to estimate the rate of convergence even if the convergence is satisfied. Second, the running time cost is increased intolerablely in drawing largescale graphs, and therefore the advantages of the force-directed approach are limited in practice. This paper is focused on these problems and presents a sufficient condition for ensuring the convergence of iterations. We then develop a practical heuristic algorithm for speeding up the iteration in force-directed approach using a successive over-relaxation (SOR) strategy. The results of computational tests on the several benchmark graph datasets used widely in graph drawing research show that our algorithm can dramatically improve the performance of force-directed approach by decreasing both the number of iterations and running time, and is 1.5 times faster than the latter on average.

关键词： graph drawing graph layout successive over-relaxation force-directed algorithm

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Towards estimating expected sizes of probabilistic skylines

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Science China(Information Sciences) 2011年第12期54卷 2574-2584页

作者： YANG YongTao & WANG YiJie national Key {1.oratory for parallel and distributed processing, School of Computer, national University of Defense Technology, Changsha 41.073, China 1. National Key Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha 410073 China

We consider the maximal vector problem on uncertain data, which has been recently posed by the study on processing skyline queries over a probabilistic data stream in the database context. Let D n be a set of n points in a d-dimensional space and q (0 < q 1. be a probability threshold; each point in D n has a probability to occur. Our problem is concerned with how to estimate the expected size of the probabilistic skyline, which consists of all the points that are not dominated by any other point in D n with a probability not less than q. We prove that the upper bound of the expected size is O(min{n, (- ln q)(ln n) d-1.}) under the assumptions that the value distribution on each dimension is independent and the values of the points along each dimension are distinct. The main idea of our proof is to find a recurrence about the expected size and solve it. Our results reveal the relationship between the probability threshold q and the expected size of the probabilistic skyline, and show that the upper bound is poly-logarithmic when q is not extremely small.

关键词： probabilistic skyline probabilistic data streams expected size

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A logistic regression model for Semantic Web service matchmaking

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Science China(Information Sciences) 2012年第7期55卷 1715-1720页

作者： WEI DengPing 1.,WANG Ting 1.& WANG Ji 2 1.School of Computer,national University of Defense Technology,Changsha 41.073,China 2 national laboratory for parallel and distributed processing,Changsha 41.073,China 1. School of Computer National University of Defense Technology Changsha 410073 China2. National Laboratory for Parallel and Distributed Processing Changsha 410073 China

Semantic Web service matchmaking,as one of the most challenging problems in Semantic Web services (SWS),aims to filter and rank a set of services with respect to a service query by using a certain matching *** this paper,we propose a logistic regression based method to aggregate several matching strategies instead of a fixed integration (e.g.,the weighted sum) for SWS *** logistic regression model is trained on training data derived from binary relevance assessments of existing test collections,and then used to predict the probability of relevance between a new pair of query and service according to their matching values obtained from various matching *** are then ranked according to the probabilities of relevance with respect to each *** method is evaluated on two main test collections,SAWSDL-TC2 and Jena Geography Dataset(JGD).Experimental results show that the logistic regression model can effectively predict the relevance between a query and a service,and hence can improve the effectiveness of service matchmaking.

关键词： Semantic Web service matchmaking logistic regression

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Survey of DHT topology construction techniques in virtual computing environments

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Science China(Information Sciences) 2011年第11期54卷 2221-2235页

作者： ZHANG YiMing 1.2,LU XiCheng 1.2 & LI DongSheng 1.21.national {1.oratory for parallel and distributed processing (PDL),Changsha 41.073,China 2 School of Computer,national University of Defense Technology,Changsha 41.073,China 1. National Laboratory for Parallel and Distributed Processing (PDL) Changsha 410073 China2. School of Computer National University of Defense Technology Changsha 410073 China

The Internet-based virtual computing environment (iVCE) is a novel network computing *** characteristics of growth,autonomy,and diversity of Internet resources present great challenges to resource sharing in *** DHT overlay (DHT for short) technique has various advantages such as high scalability,low latency,and desirable availability,and is thus an important approach to realizing efficient resource *** construction is a key technique for structured overlays that realizes basic overlay functions including dynamic maintenance and message *** this paper,we first introduce the traditional techniques of DHT topology construction,focusing mainly on dynamic maintenance and message routing of typical DHTs,DHT indexing techniques for complex queries,and DHT grouping techniques for matching domain *** then present recent advances in DHT topology construction techniques in iVCE taking advantage of the characteristics of Internet ***,we discuss the future of DHT topology construction techniques.

关键词： virtual computing environments DHT overlays topology construction distributed indexing flexible routing

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