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Independent global constraints-aware web service composition optimization

Information Technology Journal 2009年第2期8卷 181-187页

作者： Fang, Xianwen Jiang, Changjun Fan, Xiaoqin Department of Computer Science and Technology Tongji University Shanghai 201804 China Key Lab of Embedded System and Service Computing Ministry of Education Shanghai 201804 China Department of Information and Computer Science Anhui University of Science and Technology Huainan Anhui 232001 China

In semi-automatic service composition, developers should construct the process model according to concrete application requirement and then the instance services are bound automatically for every abstract task and make the composite service with optimal performance. This study presents independent global constrains-aware Web service composition method based on associate Petri net (APN) and genetic algorithm (GA). Firstly, an APN modeling methods which can describe multi-attribute multi-constraint relations and associate relation between component services is proposed. Secondly, combining with the properties of APN, GA is used to search a legal firing sequence with the biggest trust value in the APN model and the composite service corresponding to the legal firing sequence is the optimal solution. Finally, the experimental simulation is given out. Theoretical analysis and experimental results indicate that this method owns both lower computation cost and higher success ratio of service composition. © 2009 Asian Network for Scientific Information.

关键词： Web services

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Robust analog precoding designs for millimeter wave MIMO transceivers 20

Robust analog precoding designs for millimeter wave MIMO tra...

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20th International ITG Workshop on Smart Antennas, WSA 2016

作者： Xia, Pengfei Heath, Robert W. Prelcic, Nuria Gonzalez Key Lab of Embedded System and Service Computing Tongji University Shanghai China University of Texas at Austin AustinTX United States University of Vigo Vigo Pontevedra Spain

ISBN: (纸本)9783800741779

Millimeter wave communication provides high data rates thanks to large arrays at the transmitter and receiver, coupled with large bandwidth channels. Exploiting the arrays is challenging due to the need to configure precoding at the transmitter based on the large frequency selective channel. In this paper we exploit the power iteration principle and propose a robust analog precoding training algorithm that can be applied in both frequency division duplex transmission (FDD) systems and time division duplex transmission (TDD) systems with or without RF calibration. We further analyze the convergence of the proposed algorithm and show how it converges to the singular value decomposition optimality exponentially. We propose null space projection on top of the power iteration to form multiple orthogonal beams at the transmitter and receiver. Strongest tap selection with proper energy pruning is used to collect as much precoding gain as possible from a frequency selective fading channel. The exponential effective SINR mapping performance is evaluated and demonstrates that the overall approach works effectively. Numerical simulation results demonstrate algorithm robustness and the algorithm works effectively not only for the simplified millimeter wave directional channels, but also for more general rich scattering channels. © VDE VERLAG GMBH · Berlin · Offenbach, Germany.

关键词： Millimeter waves

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Description and verification of dynamic software architectures for distributed systems

Journal of Software

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Journal of Software 2010年第7期5卷 721-728页

作者： Xu, Hongzhen Zeng, Guosun Chen, Bo Department of computer Science and Technology Tongji University Shanghai 201804 China Department of Computer Science and Technology East China Institute of Technology Fuzhou Jiangxi Province 344000 China Embedded System and Service Computing Key Lab of Ministry of Education Shanghai 201804 China

Continuing growth and increasing complexity of distributed software systems make them be more flexible, adaptive and easily extensible. Dynamic evolution or reconfiguration of distributed software systems is one possible solution to meet these demands. However, there are some challenges for building dynamically evolving distributed software systems at runtime, where dynamic software architectures for them is one of the most crucial problems. In this paper, we proposed a formal method of describing and verifying dynamic software architectures for distributed systems using hypergraph grammars. We firstly gave out reconfiguration production rules and operations for software architectures based on hypergraph grammars, and then described dynamic reconfiguration of software architectures for distributed systems according to those rules. At last we verified the invariant property of dynamic software architectures for those systems using model checking, and gave out corresponding verification algorithms. © 2010 ACADEMY PUBLISHER.

关键词： Dynamic models

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A Novel Frequency Selective Sounding Scheme for TDD LTE-Advanced systems

A Novel Frequency Selective Sounding Scheme for TDD LTE-Adva...

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IEEE Global Communications Conference

作者： Shengjie Zhao Baolong Zhou Daqiang Zhang Key Lab of Embedded System and Service Computing Ministry of Education Tongji University

ISBN: (纸本)9781479935130

In this paper we propose a novel Frequency Selective SRS (FS-SRS) scheme to improve the quality of CSI. According to the CQIs (channel quality indications), which are periodically reported by each user, and the bandwidth requirement of each user, BSs dynamically schedule each user to send SRSs only on the requisite bandwidth with best CQIs instead of on full bandwidth or on specified sub-bandwidth as in the current LTE TDD systems. Simulation results show that the proposed FS-SRS scheme outperforms the current schemes in estimation accuracy for various frequency-selective and/or time-selective fading channels. In addition, the proposed FS-SRS scheme offers unique advantages over the current schemes. Firstly, it is robust to frequency selective channels. Secondly, it is hardly impacted by timing offset. Thirdly, it is adaptive to the change of the underlying scheduler. Fourthly, it can increase SRS capacity. Finally, it can be extended to multi-user MIMO (multiple-input multiple-output) systems, called extended FS-SRS scheme. Moreover, the proposed schemes are applicable to the uplink SRS design in LTE-Advanced systems.

关键词： Channel estimation error Frequency selective Long Term Evolution (LTE) Sounding Time division duplex (TDD)

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DAG-Aware Joint Task Scheduling and Cache Management in Spark Clusters

DAG-Aware Joint Task Scheduling and Cache Management in Spar...

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International Symposium on Parallel and Distributed Processing (IPDPS)

作者： Yinggen Xu Liu Liu Zhijun Ding The Key Lab of Embedded System and Service Computing Tongji University Shanghai China

ISBN: (数字)9781728168760

ISBN: (纸本)9781728168777

Data dependency, often presented as directed acyclic graph (DAG), is a crucial application semantics for the performance of data analytic platforms such as Spark. Spark comes with two built-in schedulers, namely FIFO and Fair scheduler, which do not take advantage of data dependency structures. Recently proposed DAG-aware task scheduling approaches, notably GRAPHENE, have achieved significant performance improvements but paid little attention to cache management. The resulted data access patterns interact poorly with the built-in LRU caching, leading to significant cache misses and performance degradation. On the other hand, DAG-aware caching schemes, such as Most Reference Distance (MRD), are designed for FIFO scheduler instead of DAG-aware task *** this paper, we propose and develop a middleware Dagon, which leverages the complexity and heterogeneity of DAGs to jointly execute task scheduling and cache management. Dagon relies on three key mechanisms: DAG-aware task assignment that considers dependency structure and heterogeneous resource demands to reduce potential resource fragmentation, sensitivity-aware delay scheduling that prevents executors from long waiting for tasks insensitive to locality, and priority-aware caching that makes the cache eviction and prefetching decisions based on the stage priority determined by DAG-aware task assignment. We have implemented Dagon in Apache Spark. Evaluation on a testbed shows that Dagon improves the job completion time by up to 42% and CPU utilization by up to 46% respectively, compared to GRAPHENE plus MRD.

关键词： Task analysis Delays Sparks Data analysis Graphene Complexity theory Sensitivity

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Construct pairwise test suites based on the Bak-Sneppen model of biological evolution

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World Academy of Science, Engineering and Technology 2009年 35卷 224-229页

作者： Yuan, Jianjun Jiang, Changjun Department of Computer Science and Technology The Key Lab. of 'Embedded System and Service Computing' Ministry of Education of China Tongji University Shanghai 201804 China

Pairwise testing, which requires that every combination of valid values of each pair of system factors be covered by at lease one test case, plays an important role in software testing since many faults are caused by unexpected 2-way interactions among system factors. Although meta-heuristic strategies like simulated annealing can generally discover smaller pairwise test suite, they may cost more time to perform search, compared with greedy algorithms. We propose a new method, improved Extremal Optimization (EO) based on the Bak-Sneppen (BS) model of biological evolution, for constructing pairwise test suites and define fitness function according to the requirement of improved EO. Experimental results show that improved EO gives similar size of resulting pairwise test suite and yields an 85% reduction in solution time over SA.

关键词： Simulated annealing

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Real-time action recognition with enhanced motion vector CNNs

Real-time action recognition with enhanced motion vector CNN...

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2016 IEEE Conference on Computer Vision and Pattern Recognition, CVPR 2016

作者： Zhang, Bowen Wang, Limin Wang, Zhe Qiao, Yu Wang, Hanli Shenzhen Key Lab of Comp. Vis. and Pat. Rec. Shenzhen Institutes of Advanced Technology CAS China Key Laboratory of Embedded System and Service Computing Ministry of Education Tongji University Shanghai China Computer Vision Lab ETH Zurich Switzerland

ISBN: (纸本)9781467388511

The deep two-stream architecture [23] exhibited excellent performance on video based action recognition. The most computationally expensive step in this approach comes from the calculation of optical flow which prevents it to be real-time. This paper accelerates this architecture by replacing optical flow with motion vector which can be obtained directly from compressed videos without extra calculation. However, motion vector lacks fine structures, and contains noisy and inaccurate motion patterns, leading to the evident degradation of recognition performance. Our key insight for relieving this problem is that optical flow and motion vector are inherent correlated. Transferring the knowledge learned with optical flow CNN to motion vector CNN can significantly boost the performance of the latter. Specifically, we introduce three strategies for this, initialization transfer, supervision transfer and their combination. Experimental results show that our method achieves comparable recognition performance to the state-of-the-art, while our method can process 390.7 frames per second, which is 27 times faster than the original two-stream method.

关键词： Pattern recognition

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A comprehensive QoS determination model for Infrastructure-as-a-service clouds

A comprehensive QoS determination model for Infrastructure-a...

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2013 IEEE International Conference on Automation Science and Engineering, CASE 2013

作者： Xia, Yunni Zhou, Mengchu Luo, Xin Zhu, Qingsheng Software Theory and Technology Chongqing Key Lab Chongqing University Chongqing 400030 China Key Laboratory of Embedded System and Service Computing Ministry of Education Tongji University Shanghai 201804 China Department of Electrical and Computer Engineering New Jersey Institute of Technology Newark NJ 07102 United States

ISBN: (纸本)9781479915156

Cloud computing is a recently developed new technology for complex systems with massive service sharing, which is different from the resource sharing of the grid computing systems. In a cloud environment, service requests from users go through numerous provider specific steps from the instant it is submitted to when the service is fully delivered. Quality modeling and analysis of clouds are not easy tasks because of the complexity of the provisioning mechanism and the dynamic cloud environment. This study proposes an analytical modelbased approach for quality evaluation of Infrastructure-as-a-service cloud and consider expected request completion time, rejection probability, and system overhead rate as key QoS metrics. It also features with the modeling of different warming and cooling strategies of machines and the ability to identify the optimal balance between system overhead and performance. © 2013 IEEE.

关键词： Quality control

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Safe Reinforcement Learning with Dead-Ends Avoidance and Recovery

arXiv

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arXiv 2023年

作者： Zhang, Xiao Zhang, Hai Zhou, Hongtu Huang, Chang Zhang, Di Ye, Chen Zhao, Junqiao The Department of Computer Science and Technology Tongji University China The MOE Key Lab of Embedded System and Service Computing Tongji University China

Safety is one of the main challenges in applying reinforcement learning to realistic environmental tasks. To ensure safety during and after training process, existing methods tend to adopt overly conservative policy to avoid unsafe situations. However, overly conservative policy severely hinders the exploration, and makes the algorithms substantially less rewarding. In this paper, we propose a method to construct a boundary that discriminates safe and unsafe states. The boundary we construct is equivalent to distinguishing dead-end states, indicating the maximum extent to which safe exploration is guaranteed, and thus has minimum limitation on exploration. Similar to Recovery Reinforcement Learning, we utilize a decoupled RL framework to learn two policies, (1) a task policy that only considers improving the task performance, and (2) a recovery policy that maximizes safety. The recovery policy and a corresponding safety critic are pretrained on an offline dataset, in which the safety critic evaluates upper bound of safety in each state as awareness of environmental safety for the agent. During online training, a behavior correction mechanism is adopted, ensuring the agent to interact with the environment using safe actions only. Finally, experiments of continuous control tasks demonstrate that our approach has better task performance with less safety violations than state-of-the-art algorithms. Copyright © 2023, The Authors. All rights reserved.

关键词： Reinforcement learning

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How to Fine-tune the Model: Unified Model Shift and Model Bias Policy Optimization

arXiv

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arXiv 2023年

作者： Zhang, Hai Yu, Hang Zhao, Junqiao Zhang, Di Huang, Chang Zhou, Hongtu Zhang, Xiao Ye, Chen Department of Computer Science Tongji University Shanghai China MOE Key Lab of Embedded System and Service Computing Tongji University Shanghai China

Designing and deriving effective model-based reinforcement learning (MBRL) algorithms with a performance improvement guarantee is challenging, mainly attributed to the high coupling between model learning and policy optimization. Many prior methods that rely on return discrepancy to guide model learning ignore the impacts of model shift, which can lead to performance deterioration due to excessive model updates. Other methods use performance difference bound to explicitly consider model shift. However, these methods rely on a fixed threshold to constrain model shift, resulting in a heavy dependence on the threshold and a lack of adaptability during the training process. In this paper, we theoretically derive an optimization objective that can unify model shift and model bias and then formulate a fine-tuning process. This process adaptively adjusts the model updates to get a performance improvement guarantee while avoiding model overfitting. Based on these, we develop a straightforward algorithm USB-PO2 (Unified model Shift and model Bias Policy Optimization). Empirical results show that USB-PO achieves state-of-the-art performance on several challenging benchmark tasks. © 2023, CC BY.

关键词： Benchmarking

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