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Simulation-based evaluation of the Imagine stream processor with scientific programs

International Journal of High Performance Computing and Networking 2012年第2期7卷 99-110页

作者： Che, Yonggang Xu, Chuanfu Lu, Pingjing Wang, Zhenghua National Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha 410073 Hunan China

This paper evaluates the performance and efficiency of Imagine stream processor for scientific programs. It classifies scientific programs into three classes based on their computation to memory access ratios. Typical programs are selected and measured on a simulated Imagine and two general-purpose processors. Comparative analysis is made with special attentions on the computational efficiency, power efficiency and performance bottleneck. The results show that programs in Class 1 attain high performance and high computational efficiency on Imagine. Their performance is only restricted by limited ILP and load imbalance across ALUs. Programs in Class 2 attain moderate performance but non-satisfactory computational efficiency on Imagine due to limited LRF and SRF reuse. Programs in Class 3 attain extremely low performance on Imagine because most of the execution time is spent on DRAM accesses. The estimated power efficiency on Imagine is excellent except for programs in Class 3. Copyright © 2012 Inderscience Enterprises Ltd.

关键词： Computational efficiency

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Some critical problems of botnets

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Jisuanji Xuebao/Chinese Journal of Computers 2012年第6期35卷 1192-1208页

作者： Wang, Tian-Zuo Wang, Huai-Min Liu, Bo Shi, Pei-Chang Institute of Network and Information Security School of Computer Science National University of Defense Technology Changsha 410073 China National Laboratory for Parallel and Distributed Processing School of Computer Science National University of Defense Technology Changsha 410073 China

As a complex, flexible and effective platform for network attacking, the botnet spreads widely in the Internet. Botnets can provide the botmasters with the ability to launch large-scale malicious activities such as spamming and DDoS (distributed Denial of Service) attacks. Botnets are continuously bringing more and more severe threats, so that the study on botnets has already become one of the focuses in the field of network security. However, in recent years, some new developments of botnets are challenging the existing understanding on botnets. In this paper, according to the new conditions of botnets and the researches in existence, a definition of botnet is proposed based on the works of other researchers, taxonomies of botnets are introduced respectively from the views of network structure, dependency and delivery pattern of C&C (Command and Control) information. Then the techniques on detecting, measuring and restraining botnets are analyzed systematically. In the end, we give the evolution trends of botnets and the future research trends in this area.

关键词： Botnet

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UCBench: A user-centric benchmark suite for C code static analyzers

UCBench: A user-centric benchmark suite for C code static an...

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International Conference on Information science and technology (ICIST)

作者： Jiangchao Liu Liqian Chen Longming Dong Ji Wang National Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha China

In recent years, many C code static analyzers, with different abilities of bug detection, have appeared and been applied in various domains. There are so many choices that it becomes hard for programmers to know in detail the strengths as well as limitations of all these analyzers and to find the most suitable ones for their code. In this paper, we propose a benchmark for C code static analyzers, named UCBench, to provide quantitative and qualitative measurements for evaluating analyzers. Being different from other benchmarks, UCBench concentrates more on users' requirements rather than the improvements of bug detecting technique itself. The major components of UCBench include test case database, evaluation metrics and harness. We classify test cases into several groups according to their attributes and design various user-centric evaluation metrics. Besides, we develop some harness to automate the evaluation process. Finally, we demonstrate our benchmark suite over four C code static analyzers: Flawfinder, Cppcheck, Uno and Splint.

关键词： Benchmark testing Libraries Measurement Computer bugs Databases Standards Monitoring

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Precise pointer analysis for list-manipulating programs based on quantitative separation logic

Precise pointer analysis for list-manipulating programs base...

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International Conference on Information science and technology (ICIST)

作者： Longming Dong Liqian Chen Jiangchao Liu Renjian Li National Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha China

Full precise pointer analysis has been a challenging problem, especially when dealing with dynamically-allocated memory. Separation logic can describe pointer alias formally, but cannot describe the quantitative reachability between pointers. In this paper, we present a symbolic framework for analyzing the reachability between pointers in list-manipulating programs. The precise points-to relations of pointers in lists are described by formulae of quantitative separation logic (QSL), and the analysis framework is based on the operational and rearrangement rules about the assignments of pointers. The fixpoint calculus and the counter symbolic abstraction are used to find loop invariants. We can get precise relations between pointers at each point of list-manipulating programs. In the end, several initial examples about list-manipulating programs are given to show that the approach can get precise pointer analysis for list-manipulating programs.

关键词： Radiation detectors Shape Instruments Calculus Semantics Data structures Argon

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Invalid Pointer Dereferences Detection for CPS Software Based on Extended Pointer Structures

Invalid Pointer Dereferences Detection for CPS Software Base...

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International Conference on Secure Software Integration and Reliability Improvement Companion (SSIRI-C)

作者： Longming Dong Wei Dong Liqian Chen National Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha China

Invalid pointer dereferences, such as null pointer dereferences, dangling pointer dereferences and double frees, are a prevalent source of software bugs in CPS software, due to flexible dereferencing pointers along various pointer fields. Existing tools have high overhead or are incomplete, thereby limiting their efficiency in checking the kind of CPS software with shared and mutable memory. In this paper, we present a novel extended pointer structure for detecting all invalid pointer dereferences in this kind of CPS software. We propose an invalid pointer dereferences detection algorithm based on the uniform transformation of abstract heap states. Experimental evaluation about a set of large C benchmark programs shows that the proposed approach is sufficiently efficient in detecting invalid pointer dereferences of CPS software with shared and mutable memory.

关键词： Abstracts Software Frequency modulation Semantics Switches Detection algorithms Runtime

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SMP-SIM: An event-driven performance simulator for SMP

SMP-SIM: An event-driven performance simulator for SMP

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International Conference on Systems and Informatics (ICSAI)

作者： Xin Zhang Yuhua Tang Yufei Lin Xinhai Xu Xiaowei Guo Xiaoguang Ren National Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha Hunan China

Performance prediction for the high performance computer system is of great importance for designing, implementing, and optimizing system. As a widely used technique for predicting performance, simulation method attracts more and more attention from the research community. Based on analyzing the problems in the current performance simulation techniques, we present a key idea of the performance simulator for SMP system based on event-driven. We propose the framework of SMP-SIM and implement it based on MPICH2. The simulation results show that, our simulation technique has the advantages of high accuracy and simulation performance.

关键词： Computational modeling Switches Clocks Educational institutions Computers Predictive models Analytical models

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Bodhi: Detecting Buffer Overflows with a Game

Bodhi: Detecting Buffer Overflows with a Game

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International Conference on Secure Software Integration and Reliability Improvement Companion (SSIRI-C)

作者： Jie Chen Xiaoguang Mao School of Computer National University of Defense Technology Changsha China National Laboratory for Parallel and Distributed Processing Changsha China

Buffer overflow is one of the most dangerous and common vulnerabilities in CPS software. Despite static and dynamic analysis, manual analysis is still heavily used which is useful but costly. Human computation harness humans' time and energy in a way of playing games to solve computational problems. In this paper we propose a human computation method to detect buffer overflows that does not ask a person whether there is a potential vulnerability, but rather a random person's idea. We implement this method as a game called Bodhi in which each player is shown a piece of code snippet and asked to choose whether their partner would think there is a buffer overflow vulnerability at a given position in the code. The purpose of the game is to make use of the rich distributed human resource to increase effectiveness of manual detection for buffer overflows. The game has been proven to be efficient and enjoyable in practice.

关键词： Games Buffer overflow Humans Software Servers Manuals Programming

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DMSS: A Dynamic Memory Scheduling System in Server Consolidation Environments

DMSS: A Dynamic Memory Scheduling System in Server Consolida...

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IEEE International Symposium on Object/Component/Service-Oriented Real-Time distributed Computing Workshops (ISORCW)

作者： Lanzheng Liu Rui Chu Yongchun Zhu Pengfei Zhang Liufeng Wang National Laboratory for Parallel and Distributed Processing National University of Defense Technology Changsha China Systems and Technology Group IBM China Beijing China

As the foundation of cloud computing, Server consolidation allows multiple computer infrastructures running as virtual machines in a single physical node. It improves the utilization of most kinds of resource but memory under x86 architecture. Because of inaccurate memory usage estimate and the lack of memory resource management, there is much service performance degradation in data centers, even though they have occupied a large amount of memory. Furthermore, memory becomes insufficient for a physical server when a lot of virtual machines depend on it. In order to improve this, we present a dynamic memory scheduling system called DMSS, which can manage memory resources in server consolidation environments and allocate memory among virtual machines on demand. We have designed and implemented the corresponding memory scheduling policy based on Xen virtualization platform to enhance memory efficiency and achieve service level agreement. The benchmark shows that DMSS can make an accurate and rapid response to memory changes and save more than 30% physical memory with less than 5% performance degradation. DMSS actually brings in economic benefits to cloud service providers because more virtual machines can be accommodated at lower costs.

关键词： Memory management Virtual machine monitors Monitoring Resource management Servers Dynamic scheduling Degradation

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Reduced complexity tree-structured conditional random field for all-words word sense disambiguation

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Journal of Computational Information Systems 2012年第3期8卷 1177-1186页

作者： Zhou, Yun Wang, Ting Wang, Zhiyuan Xie, Songxian Computer School National University of Defense Technology Changsha 410073 China National Key Laboratory for Parallel and Distributed Processing National University of Defense Technology Changsha 410073 China

In this paper, we apply tree-structured conditional random field (TCRF) to all-words word sense disambiguation (WSD), where the graphical structure of TCRF is the dependency syntax tree produced by Minipar. The extremely large label space and high time complexity of TCRF hinders its application in semantic parsing, especially in all-words WSD, and we focus on reducing the time complexity of TCRF in this paper. The running time of TCRF is reduced significantly by edge feature selection and parallelization in training phase and beam search strategy in decoding phase. We evaluate the TCRF method on the English all-words task of Senseval-3, and the F1 value of TCRF method is 0.668, which outperforms the best result 0.652 in Senseval-3. For convenience of comparison, our training set only includes a part of Semcor, which reserves the space for improvement. Furthermore, the practical problem in the fields of information retrieval and natural language processing, often has a large label space and tree-structured information, which can also be solved by the TCRF method proposed in this paper. 1553-9105/Copyright © 2012 Binary Information Press.

关键词： Semantics

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A malicious code detection method based on statistical analysis

A malicious code detection method based on statistical analy...

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International Conference on Fuzzy Systems and Knowledge Discovery (FSKD)

作者： Yunlong Wu Chen Chen Huiquan Wang Jie Zhou Xinhai Xu National Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha Hunan 410073 China National Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha Hunan P. R. China School of Computer National University of Defense Technology Changsha Hunan 410073 China

The malicious code detection based on behaviors has proved effective. But there are high false positives and high false negatives when using this method. Because the behaviors are always out-of-order and redundant. To solve these problems, this paper proposes a detection method based on statistical analysis. Firstly, this method uses association rules to sort out the behaviors, and then we can get the integrated and accurate behavior sequences. Secondly, by using the association algorithm we can pick up the signatures of behavior sequences. In addition, this method can detect the signatures to judge the threat based on statistical analysis. Experimental results indicate that it can reduce both the false positives and the false negatives effectively.

关键词： Mathematical model Statistical analysis Equations Association rules Educational institutions Algorithm design and analysis Estimation

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