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IEEE International Conference on Computational Science and Engineering, CSE

作者： Yong Lu Shaohe Lv Xiaodong Wang Xingming Zhou Science and Technology on Parallel and Distributed Processing Laboratory National University of Defense Technology Changsha Hunan China

ISBN: (纸本)9781479979820

In consideration of the continuous increasing demand of wireless data transmission, ultra-wideband spectrum sensing is crucial to support the cognitive communication in a ultra-wide frequency band. However, it is challenging to design ADCs that fulfill the Nyquist rate requirement for a ultra wide band. Spectrum sensing based on the sub-Nyquist sampling maybe the answer. We propose UWBSS: ultra-wideband spectrum sensing. With multiple sub-Nyquist sampling rates, UWBSS can reconstruct the occupied frequencies from the under sampled data directly without complex amplitudes reconstruction. Also We conduct an extensive study to characterize the effect on the accuracy of sub-Nyquist spectrum sensing of sampling rate, bandwidth resolution and the SNR of the original signal. The performance of UWBSS is verified by simulations.

关键词： Sensors Signal to noise ratio Ultra wideband technology Signal resolution Wideband Energy resolution

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Agent-Based Fault Tolerance Mechanism for distributed key-Value Database

Agent-Based Fault Tolerance Mechanism for Distributed Key-Va...

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International Conference on Digital Home (ICDH)

作者： Wu Hui-jun Lu Kai GenLi Gen Jiang Jin-fei Wang Shuang-xi Science and Technology on Parallel and Distributed Processing Laboratory National University of Defense Technology Changsha PR China

ISBN: (纸本)9781479942831

distributed key-value database is widely used in Web 2.0 applications and cloud computing environments. It overcomes the weak performance and bad scalability of traditional relational database. But fault in distributed system will lead to errors, then the high performance is useless. So we should build a fault tolerance mechanism. On the other hand, in many application scenarios, transactional operations are inevitable. Some existing key-value databases utilize two-phase commit protocol or optimistic concurrency control in transaction processing. But the problems are sing-node failure and high overhead in protocol processing. Meanwhile, users' programming becomes more error-prone. This paper designs a fault tolerance and recovery mechanism on DStageDB, which is a distributed key-value database. We design an agent-based transaction processing mechanism. The transaction processing speed is improved and less user intervention is needed.

关键词： Servers Fault tolerance Fault tolerant systems distributed databases Protocols Usability

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Hierarchical categorization of open source software by online profiles

Hierarchical categorization of open source software by onlin...

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作者： Wang, Tao Wang, Huaimin Yin, Gang Yang, Cheng Li, Xiang Zou, Peng Science and Technology on Parallel and Distributed Processing Laboratory National University of Defense Technology Changsha 410073 China Department of Computer Science University of Western Ontario London ON N6A 5B7 Canada Academy of Equipment Beijing 100000 China

The large amounts of freely available open source software over the Internet are fundamentally changing the traditional paradigms of software development. Efficient categorization of the massive projects for retrieving relevant software is of vital importance for Internet-based software development such as solution searching, best practices learning and so on. Many previous works have been conducted on software categorization by mining source code or byte code, but were verified on only relatively small collections of projects with coarse-grained categories or clusters. However, Internet-based software development requires finer-grained, more scalable and language-independent categorization approaches. In this paper, we propose a novel approach to hierarchically categorize software projects based on their online profiles. We design a SVMbased categorization framework and adopt a weighted combination strategy to aggregate different types of profile attributes from multiple repositories. Different basic classification algorithms and feature selection techniques are employed and compared. Extensive experiments are carried out on more than 21,000 projects across five repositories. The results show that our approach achieves significant improvements by using weighted combination. Compared to the previous work, our approach presents competitive results with more finer-grained and multi-layered category hierarchy with more than 120 categories. Unlike approaches that use source code or byte code, our approach is more effective for large-scale and languageindependent software categorization. In addition, experiments suggest that hierarchical categorization combined with general keyword-based searching improves the retrieval efficiency and accuracy. Copyright © 2014 The Institute of Electronics, Information and Communication Engineers.

关键词： Open source software

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A Discrete Data Dividing Approach for Erasure-Code-Based Storage Applications

A Discrete Data Dividing Approach for Erasure-Code-Based Sto...

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2014 IEEE 8th International Symposium on Service Oriented System Engineering

作者： Weidong Sun Yijie Wang Yongquan Fu Xiaoqiang Pei Science and Technology on Parallel and Distributed Processing Laboratory National University of Defense Technology Changsha Hunan P. R. China

Erasure codes are promising for improving the reliability of the storage system due to its space efficiency compared to the replication methods. Traditional erasure codes split data into equalsized data blocks and encode strips in different data blocks. This brings heavy repairing traffic when clients read parts of the data, since most strips read for repairing are not in the expected blocks. This paper proposes a novel discrete data dividing method to completely avoid this problem. The key idea is to encode strips from the same data block. We could see that for repairing failed blocks, the strips to be read are either in the same data block with corrupted strips or from the encoded strips. Therefore, no data is wasted. We design and implement this data layout into a HDFS-like storage system. Experiments over a small-scale testbed shows that the proposed discrete data divided method avoids downloading data blocks that are not needed for clients during the repairing operations.

关键词： Strips Decoding Encoding distributed databases Writing Reliability Magnetic heads

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Efficient parallel implementation of morphological operation on GPU and FPGA

Efficient parallel implementation of morphological operation...

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International Conference on Security, Pattern Analysis, and Cybernetics (SPAC)

作者： Teng Li Yong Dou Jingfei Jiang Jing Gao National Laboratory for Parallel & Distributed Processing National University of Defense and Technology Changsha China Information Management Department AIR CHINA LIMITED Beijing China

Morphological operation constitutes one of a powerful and versatile image and video applications applied to a wide range of domains, from object recognition, to feature extraction and to moving objects detection in computer vision where real-time and high-performance are required. However, the throughput of morphological operation is constrained by the convolutional characteristic. In this paper, we analysis the parallelism of morphological operation and parallel implementations on the graphics processing unit (GPU), and field programming gate array (FPGA) are presented. For GPU platform, we propose the optimized schemes based on global memory, texture memory and shared memory, achieving the throughput of 942.63 Mbps with 3×3 structuring element. For FPGA platform, we present an optimized method based on the traditional delay-line architecture. For 3×3 structuring element, it achieves a throughput of 462.64 Mbps.

关键词： Graphics processing units Morphological operations Field programmable gate arrays Throughput Optimization Instruction sets Random access memory

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MCHITS: Monte carlo based method for hyperlink induced topic search on networks

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Journal of Networks 2013年第10期8卷 2376-2382页

作者： Jin, Zhaoyan Shi, Dianxi Wu, Quanyuan Fan, Hua National Key Laboratory for Parallel and Distributed Processing School of Computer National University of Defense Technology Changsha 410073 China

Hyperlink Induced Topic Search (HITS) is the most authoritative and most widely used personalized ranking algorithm on networks. The HITS algorithm ranks nodes on networks according to power iteration, and has high complexity of computation. This paper models the HITS algorithm with the Monte Carlo method, and proposes Monte Carlo based algorithms for the HITS computation. Theoretical analysis and experiments show that the Monte Carlo based approximate computing of the HITS ranking reduces computing resources a lot while keeping higher accuracy, and is significantly better than related works. © 2013 ACADEMY PUBLISHER.

关键词： Monte Carlo methods

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Flexible Virtual Channel Power-Gating for High-Throughput and Low-Power Network-on-Chip

Flexible Virtual Channel Power-Gating for High-Throughput an...

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Euromicro Symposium on Digital System Design

作者： Feng Wang Xiantuo Tang Qinglin Wang Zuocheng Xing Hengzhu Liu Science and Technology on Parallel and Distributed Processing Laboratory National University of Defense Technology Changsha Hunan P. R. China

Power-gating is a representative circuit level technique to mitigate leakage power. While in low-power Network-on-Chip (NoC) design, the former fine-grained power-gating methods will decrease network performance due to serial wake-up latency and head-of-line blocking. Therefore, we propose a flexible Virtual Channel (VC) management scheme for fine-grained power-gating to achieve high throughput and low-power. The proposed power-gating method with the early wake-up is evaluated by using some synthetic workloads. When compared with an optimized early wake-up power-gating technique, it can improve performance effectively in medium and high network loads, and increases the network throughput by 15.7%~44.1% for different synthetic loads, while keeps network power consumption as low as the optimized method. For the PARSEC application traces of token based protocol, it can significantly decrease packet latency by 20.3% on average, however only increases less than 3.6% peak power when compared with the optimized method.

关键词： Throughput Radiation detectors Routing Process control Pipelines Power demand Ports (Computers)

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Synchronization Error Detection of MPI Programs by Symbolic Execution

Synchronization Error Detection of MPI Programs by Symbolic ...

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Asia-Pacific Conference on Software Engineering

作者： Xianjin Fu Zhenbang Chen Chun Huang Wei Dong Ji Wang College of Computer National University of Defense Technology Changsha China Science and Technology on Parallel and Distributed Processing Laboratory National University of Defense Technology Changsha China

ISBN: (纸本)9781479974276

Asynchrony based overlapping of computation and communication is commonly used in MPI applications. However, this overlapping introduces synchronization errors frequently in asynchronous MPI programming. In this paper, we propose a symbolic execution based method for detecting input-related synchronization errors. The path space of an MPI program is systematically explored, and the related operations of the synchronization errors in the program are checked specifically. In addition, two optimizations are proposed to improve the efficiency. We have implemented our method as a prototype tool based on the symbolic executor Cloud9. The results of the extensive experiments indicate the effectiveness of our method.

关键词： Synchronization Data communication Libraries Optimization Buffer storage Prototypes Schedules

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RAFlow: Read Ahead Accelerated I/O Flow through Multiple Virtual Layers

RAFlow: Read Ahead Accelerated I/O Flow through Multiple Vir...

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International Conference on Networking, Architecture, and Storage (NAS)

作者： Zhaoning Zhang Kui Wu Huiba Li Jinghua Feng Yuxing Peng Xicheng Lu National Key Laboratory for Parallel and Distributed Processing National University of Defense Technology China Computer Science Department University of Victoria B.C. Canada National Super Computing Center Tianjin China

Virtualization is the foundation for cloud computing, and the virtualization can not be achieved without software defined, elastic, flexible and scalable virtual layers. Unfortunately, if multiple virtual storage devices are chained together, the system may be subject to severe performance degradation. While the read-ahead (RA) mechanism in storage devices plays a very important role to improve I/O performance, RA may not be effective as expected for multiple virtualization layers, since it is originally designed for one layer only. When I/O requests are passed through a long I/O path, they may trigger a chain reaction and lead to unnecessary data transmission and thus bandwidth waste. In this paper, we study the dynamic behavior of RA through multiple I/O layers and demonstrate that if controlled well, RA can greatly accelerate I/O speed. We present RAFlow, a RA control mechanism, to effectively improve I/O performance by strategically expanding RA window at each layer. Our real-world experiments show that it can achieve 20% to 50% performance improvement in I/O paths with up to 8 virtualized storage devices.

关键词： Radio access networks Acceleration distributed databases Performance evaluation Synchronization Benchmark testing Degradation

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Accuracy evaluation of deep belief networks with fixed-point arithmetic

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Computer Modelling and New Technologies 2014年第6期18卷 7-14页

作者： Jiang, Jingfei Hu, Rongdong Mikel, Lujan Dou, Yong Science and Technology on Parallel and Distributed Processing Laboratory National University of Defense Technology ChangSha Hunan China University of Manchester Manchester United Kingdom

Deep Belief Networks (DBNs) are state-of-art Machine Learning techniques and one of the most important unsupervised learning algorithms. Training DBNs is computationally intensive which naturally leads to investigate FPGA acceleration. Fixed-point arithmetic can be used when implementing DBNs in FPGAs to reduce execution time, but it is not clear the implications for accuracy. Previous studies have focused only on accelerators using some fixed bit-widths. A contribution of this paper is to demonstrate the bit-width effect on various configurations of DBNs in a comprehensive way by experimental evaluation. Explicit performance changing points are found using various bit-widths. The impact of sigmoid function approximation, required part of DBNs, is evaluated. A solution of mixed bit-widths DBN is proposed, fitting the bit-widths of FPGA primitives and gaining similar performance to the software implementation. Our results provide a guide to inform the design choices on bit-widths when implementing DBNs in FPGAs documenting clearly the trade-off in accuracy.

关键词： Field programmable gate arrays (FPGA)

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