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作者： Häubl, Christian Wimmer, Christian Mössenböck, Hanspeter Institute for System Software Christian Doppler Laboratory for Automated Software Engineering Johannes Kepler University Linz Austria

In several Java VMs, strings consist of two separate objects: metadata such as the string length are stored in the actual string object, while the string characters are stored in a character array. This separation causes an unnecessary overhead. Each string method must access both objects, which leads to a bad cache behavior and reduces the execution speed. We propose to merge the character array with the string's metadata object at run time. This results in a new layout of strings with better cache performance, fewer field accesses, and less memory overhead. We implemented this optimization for Sun Microsystems' Java HotSpot™ VM, so that the optimization is performed automatically at run time and requires no actions on the part of the programmer. The original class String is transformed into the optimized version and the bytecodes of all methods that allocate string objects are rewritten. All these transformations are performed by the Java HotSpot™ VM when a class is loaded. Therefore, the time overhead of the transformations is negligible. Benchmarks show an improved performance as well as a reduction of the memory usage. The performance of the SPECjbb2005 benchmark increases by 8%, and the average used memory after a full garbage collection is reduced by 19%. The peak performance of SPECjvm98 is improved by 8% on average, with a maximum speedup of 62%.© 2010 Elsevier B.V.

关键词： Metadata

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Trace-based compilation for the Java HotSpot virtual machine 11

Trace-based compilation for the Java HotSpot virtual machine

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9th International Conference on Principles and Practice of Programming in Java, PPPJ 2011

作者： Ḧaubl, Christian Mössenböck, Hanspeter Institute for System Software Christian Doppler Laboratory for Automated Software Engineering Johannes Kepler University Linz Austria

ISBN: (纸本)9781450309356

Traditional method-based just-in-time (JIT) compilation translates whole methods to optimized machine code. Trace-based compilation only generates machine code for frequently executed paths, so-called traces, that may span multiple methods. In this paper, we present our implementation of a trace-based JIT compiler in which we modified the mature, method-based Java HotSpot client compiler. To simplify trace recording, we added a bytecode preprocessing step that detects and directly marks loops within the bytecodes. We duplicated the existing bytecode interpreter and instrumented it for trace recording. In our implementation, traces can be anchored both at loop headers and at method entries. When a trace anchor has been executed frequently enough, trace recording is started. After several times of trace recording, our modified JIT compiler merges the recorded traces into a structure suitable for compilation. During compilation, trace-specific optimizations are applied and guarded with runtime checks if necessary. The generated machine code is then invoked by the interpreter or by already compiled traces. If a method part must be executed that was not covered by traces and therefore not compiled, or if a runtime guard fails, execution falls back to the interpreter. Benchmarks show an improved performance, less generated machine code and faster compilation compared to the methodbased Java HotSpot client compiler. The peak performance of the SPECjvm2008 benchmarks is increased by 9% on average, while 29% less machine code is generated. Similarly, the performance of the SPECjbb2005 benchmark is increased by 13% and the DaCapo 9.12 Bach benchmarks show a peak performance increase of 5% on average. © 2011 ACM.

关键词： Virtual machine

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Composition mechanisms classified by their contributor provision characteristics

Composition mechanisms classified by their contributor provi...

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2012 IEEE 10th Jubilee International Symposium on Intelligent systems and Informatics, SISY 2012

作者： Löberbauer, M. Wolfinger, R. Jahn, M. Mössenböck, H. Christian Doppler Laboratory for Automated Software Engineering Institute for System Software Johannes Kepler University Linz Austria

ISBN: (纸本)9781467347518

Composition is the process, which assembles a program from components by matching the requests of host with the provisions of contributors. The way in which contributors are provided differs, depending on the used composition mechanism. This paper defines a classification of composition mechanisms and describes what provision characteristics are typical for them. This classification is preparatory work for research in testing of component-based software, where the typical defects for composition mechanisms will be investigated. © 2012 IEEE.

关键词： software testing

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Robust Dynamic Broadcasting for Multi-Hop Wireless Networks Under Time-Varying Connectivity and Dynamic SINR

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IEEE Transactions on Mobile Computing 2025年

作者： Tian, Xiang Yu, Jiguo Luo, Chuanwen Yu, Dongxiao Wang, Guijuan Feng, Bin Jinan250353 China Shandong Fundamental Research Center for Computer Science Shandong Provincial Key Laboratory of Industrial Network and Information System Security Jinan250353 China University of Electronic Science and Technology of China School of Information and Software Engineering Chengdu610054 China Qilu University of Technology Big Data Institute Jinan250353 China Beijing Forestry University School of Information Science and Technology Beijing100083 China Shandong University School of Computer Science and Technology Shandong Qingdao266237 China Taishan University School of Information Science and Technology 271000 China

Throughput-optimal dynamic broadcasting is an essential cornerstone for the efficient operation of Multi-hop Wireless Networks (MWNs). Most existing algorithms for this problem were developed assuming static interference environments and network connectivity. However, wireless interference environments and network connectivity are inherently time-varying in real-world scenarios, primarily due to uncontrollable interference sources and unreliable links. Such time-varying characteristics make these existing algorithms less robust. In this paper, we study the robust throughput-optimal dynamic broadcasting for MWNs with multi-dimensional time-varying characteristics in terms of interference environments, network connectivity, and data arrival. We model the time-varying link existence states using a random process and characterize the time-varying interference environments through a dynamic variant of the classical Signal-to-Interference-plus-Noise-Ratio (SINR) model. In this variant, the SINR model parameters are dynamically adjusted over time by an adversary. Based on this, we first design a Robust Throughput-optimal Dynamic Broadcast (RTDB) algorithm which makes efficient slot-based max-weight link scheduling, power allocation, and data forwarding decisions in each time slot. We then prove its throughput-optimality in time-varying acyclic directed MWNs under the dynamic SINR model. The effectiveness of RTDB is validated via numerous simulations. © 2002-2012 IEEE.

关键词： Signal to noise ratio

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Hierarchical Clustering of Complex Symbolic Data and Application for Emitter Identification

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Journal of Computer Science & Technology 2018年第4期33卷 807-822页

作者： Xin Xu Jiaheng Lu Wei Wang Laboratory of Science and Technology on Information System Engineering Nanjing Research Institute of Electronics Engineering Nanjing 21000~ China Department of Computer Science University of Helsinki Helsinki 00014 Finland State Key Laboratory for Novel Software and Technology Nanjing University Nanjing 210046 China

It is well-known that the values of symbolic variables may take various forms such as an interval, a set of stochastic measurements of some underlying patterns or qualitative multi-values and so on. However, the majority of existing work in symbolic data analysis still focuses on interval values. Although some pioneering work in stochastic pattern based symbolic data and mixture of symbolic variables has been explored, it still lacks flexibility and computation efficiency to make full use of the distinctive individual symbolic variables. Therefore, we bring forward a novel hierarchical clustering method with weighted general Jaccard distance and effective global pruning strategy for complex symbolic data and apply it to emitter identification. Extensive experiments indicate that our method has outperformed its peers in both computational efficiency and emitter identification accuracy.

关键词： symbolic data analysis stochastic pattern fuzzy interval hierarchical clustering emitter identification

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A Novel Rolling Bearing Vibration Impulsive Signals Detection Approach Based on Dictionary Learning

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IEEE/CAA Journal of Automatica Sinica 2021年第6期8卷 1188-1198页

作者： Chuan Sun Hongpeng Yin Yanxia Li Yi Chai School of Big Data&Software Engineering Chongqing UniversityChongqing 401331China Key Laboratory of Complex System Safety and Control Ministry of EducationChongqing UniversityChongqing 400044China

The localized faults of rolling bearings can be diagnosed by its vibration impulsive ***,it is always a challenge to extract the impulsive feature under background noise and non-stationary *** paper investigates impulsive signals detection of a single-point defect rolling bearing and presents a novel data-driven detection approach based on dictionary *** overcome the effects harmonic and noise components,we propose an autoregressive-minimum entropy deconvolution model to separate harmonic and deconvolve the effect of the transmission *** address the shortcomings of conventional sparse representation under the changeable operation environment,we propose an approach that combines K-clustering with singular value decomposition(K-SVD)and split-Bregman to extract impulsive components *** experiments on synthetic signals and real run-to-failure signals,the excellent performance for different impulsive signals detection verifies the effectiveness and robustness of the proposed ***,a comparison with the state-of-the-art methods is illustrated,which shows that the proposed approach can provide more accurate detected impulsive signals.

关键词： Dictionary learning impulsive signals detection Kclustering with singular value decomposition(K-SVD) minimum entropy deconvolution rolling bearing signal processing

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Pinning consensus analysis of multi-agent networks with arbitrary topology

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Chinese Physics B 2013年第9期22卷 183-189页

作者：纪良浩廖晓峰陈欣 State Key Laboratory of Power Transmission Equipment & System Security and New Technology College of Computer ScienceChongqing University Chongqing key Laboratory of Computational Intelligence (Chongqing University of Posts and Telecommunications) School of Software Engineering Chongqing University

In this paper the pinning consensus of multi-agent networks with arbitrary topology is investigated. Based on the properties of M-matrix, some criteria of pinning consensus are established for the continuous multi-agent network and the results show that the pinning consensus of the dynamical system depends on the smallest real part of the eigenvalue of the matrix which is composed of the Laplacian matrix of the multi-agent network and the pinning control gains. Meanwhile, the relevant work for the discrete-time system is studied and the corresponding criterion is also obtained. Particularly, the fundamental problem of pinning consensus, that is, what kind of node should be pinned, is investigated and the positive answers to this question are presented. Finally, the correctness of our theoretical findings is demonstrated by some numerical simulated examples.

关键词： multi-agent pinning control consensus synchronization

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Optimized instrumentation of runtime verification

Optimized instrumentation of runtime verification

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2nd International Conference on Precision Mechanical Instruments and Measurement Technology, ICPMIMT 2014

作者： Gu, Wen Di Luo, Yi Gui Laboratory of Embedded System School of Software Engineering Tongji University Shanghai 201804 China

ISBN: (纸本)9783038351948

Runtime verification checks whether one system execution conforms to a group of specific requirements. One of the many problems concerned is how to lower the costly instrumentation overhead, because the performance is as important as correctness. The solutions to cope with the problem include static checking, and hardware based instrumentation. What makes a difference to our approach is that it takes into account the modular structure of the observed run, and our approach makes a tradeoff between observability and cost by means of simulated annealing algorithm. The paper gives a definition of instrumentation observability in detail. The simulated annealing approach works out an optimized instructive instrumentation solution containing part of all the observing points. An experiment is conducted on the LwIP protocol stack to prove the effect of our observing strategy. © (2014) Trans Tech Publications, Switzerland.

关键词： Simulated annealing

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Supporting Various Top-k Queries over Uncertain Datasets

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Wuhan University Journal of Natural Sciences 2014年第1期19卷 84-92页

作者： LI Wenfeng FU Zufa WANG Liwei LI Deyi PENG Zhiyong State Key Laboratory of Software Engineering Wuhan University School of Computer Wuhan University International School of Software Wuhan University Institute of Electronic System Engineering of China

There have been many researches and semantics in answering top-k queries on uncertain data in various applications. However, most of these semantics must consume much of their time in computing position probability. Our approach to support various top-k queries is based on position probability distribution （PPD） sharing. In this paper, a PPD-tree structure and several basic operations on it are proposed to support various top-k queries. In addition, we proposed an approximation method to improve the efficiency of PPD generation. We also verify the effectiveness and efficiency of our approach by both theoretical analysis and experiments.

关键词： top-k queries uncertain data position probability distribution

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Optimized strings for the Java HotSpot virtual machine 08

Optimized strings for the Java HotSpot virtual machine

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6th International Conference on Principles and Practice of Programming in Java, PPPJ 2008

ISBN: (纸本)9781605582238

In several Java VMs, strings consist of two separate objects: metadata like the string length are stored in the actual string object, while the string characters are stored in a character array. This separation causes an unnecessary overhead. Each string method must access both objects, which leads to a bad cache behavior and reduces the execution speed. We propose to merge the character array with the string's metadata object at run time. This results in a new layout of strings with better cache performance, fewer field accesses, and less memory overhead. We implemented this optimization for Sun Microsystems' Java HotSpot VM, so that the optimization is performed automatically at run time and requires no actions on the part of the programmer. The original class String is transformed into the optimized version and the bytecodes of all methods that allocate string objects are rewritten. All these transformations are performed by the Java HotSpot VM when a class is loaded. Therefore, the time overhead of the transformations is negligible. Benchmarks show a reduction of the average used memory after a full garbage collection and an improved performance. The performance of the SPECjbb2005 benchmark increases by 8%, and the average used memory after a full garbage collection is reduced by 19%. The peak performance of SPECjvm98 is improved by 8% on average, with a maximum speedup of 62%. © 2008 ACM.

关键词： Metadata

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