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| 1 | 一种MongoDB应用优化策略显示文摘为了解决不断增长的文件存储需求,和高流量高并发的访问量,增强系统的响应性能,提出一种Web应用优化策略,通过MongoDB Grid FS对网站文件存储容量、可用性和可靠性进行扩展,并且通过Nginx和Keepalived,对后台访问进行负载均衡和双机热备,优化并发性能.实验表明,当并发访问数上升至80以上时,平均访问响应时间缩短9%.文件通过Nginx Gridfs进行高并发上传时非常稳定,在较大文件下载时比直接通过本地文件系统EXT4下载速度更高. | 卢至彤 李翀 柯勇 孙健英 | 2017 | 计算机系统应用2017，26，5： | 4 |
| 2 | Validation concurrency control protocol in parallel real-time database systems显示文摘In parallel real-time database systems, concurrency control protocols must satisfy time constraints as well as the integrity constraints. The authors present a validation concurrency control(VCC) protocol, which can enhance the performance of real-time concurrency control mechanism by reducing the number of transactions that might miss their deadlines, and compare the performance of validation concurrency control protocol with that of HP2PL(High priority two phase locking) protocol and OCC-TI-WAIT-50(Optimistic concurrency control-time interval-wait-50) protocol under shared-disk architecture by simulation. The simulation results reveal that the protocol the author presented can effectively reduce the number of transactions restarting which might miss their deadlines and performs better than HP2PL and OCC-TI-WAIT-50. It works well when arrival rate of transaction is lesser than threshold. However, due to resource contention the percentage of missing deadline increases sharply when arrival rate is greater than the threshold. | LEI Xiang-dong(雷向东) YUAN Xiao-li(袁晓莉) | 2002 | Journal of Central South University of Technology2002，9，3： | 3 |
| 3 | Improving Performance of a Distributed File System Using a Speculative Semantics-Based Algorithm显示文摘File-sharing semantics is used by the file systems for sharing data among concurrent client processes in a consistent manner. Session semantics is a widely used file-sharing semantics in Distributed File Systems(DFSs). The main disadvantage of session semantics is that writes to an open file are visible to the concurrent client processes only during their next session. Recently, 'linearizability semantics' was introduced in Blob Seer DFS, in which a Read Client Process(RCP) can read only a previous version of a binary large object(blob), while update operations are carried out on that blob in a concurrent manner. In this paper, we propose a new type of file-sharing semantics, namely 'speculative semantics', which permits writes to an open file to be visible to other concurrent processes provided that data consistency is not affected. In addition, we propose a new read algorithm for DFSs based on speculative semantics and a new performance measurement metric called Currency. The experimental results obtained using Blob Seer DFS indicate that the proposed read algorithm performs better than the existing read algorithm of Blob Seer DFS. | Talluri Lakshmi Siva Rama Krishna Thirumalaisamy Ragunathan Sudheer Kumar Battula | 2015 | Tsinghua Science and Technology2015，20，6： | 2 |
| 4 | System architecture for high-performance permissioned blockchains显示文摘Blockchain(BC),as an emerging distributed database technology with advanced security and reliability,has attracted much attention from experts who devoted to efinance,intellectual property protection,the internet of things(IoT)and so forth.However,the inefficient transaction processing speed,which hinders the BC’s widespread,has not been well tackled yet.In this paper,we propose a novel architecture,called Dual-Channel Parallel Broadcast model(DCPB),which could address such a problem to a greater extent by using three methods which are dual communication channels,parallel pipeline processing and block broadcast strategy.In the dual-channel model,one channel processes transactions,and the other engages in the execution of BFT.The parallel pipeline processing allows the system to operate asynchronously.The block generation strategy improves the efficiency and speed of processing.Extensive experiments have been applied to BeihangChain,a simplified prototype for BC system,illustrates that its transaction processing speed could be improved to 16K transaction per second which could well support many real-world scenarios such as BC-based energy trading system and Micro-film copyright trading system in CCTV. | Libo FENG Hui ZHANG Wei-Tek TSAI Simeng SUN | 2019 | Frontiers of Computer Science2019，13，6： | 2 |
| 5 | Polychronous automata and their use for formal validation of AADL models显示文摘This paper investigates how state diagrams can be best represented in the polychronous model of computation (MoC) and proposes to use this model for code validation of behavior specifications in architecture analysis & design language (AADL). In this relational MoC, the basic objects are signals, which are related through dataflow equations. Signals are associated with logical clocks, which provide the capability to describe systems in which components obey multiple clock rates. We propose a model of finite-state automata, called polychronous automata, which is based on clock relationships. A specificity of this model is that an automaton is submitted to clock constraints, which allows one to specify a wide range of control-related configurations, being either reactive or restrictive with respect to their control environment. A semantic model is defined for these polychronous automata, which relies on boolean algebra of clocks. Based on a previously defined modeling method for AADL software architectures using the polychronous MoC, the proposed model is used as a formal model for the AADL behavior annex. This is illustrated with a case study involving an adaptive cruise control system. | Thierry GAUTIER Clement GUY Alexandre HONORAT Paul LE GUERNIC Jean-Pierre TALPIN Loic BESNARD | 2019 | Frontiers of Computer Science2019，13，4： | 1 |
| 6 | CRF:A Scheduling of Multi-Granularity Locks in Object-Oriented Database Systems显示文摘This paper introduces a multi-granularity locking model (MGL) for concurrency control in object-oriented database system briefiy, and presents a MGL model formally. Four lockingscheduling algorithms for MGL are proposed in the paper. The ideas of single queue scheduling(SQS) and dual queue scheduling (DQS) are proposed and the algorithm and the performance evaluation for these two scheduling are presented in some paper. This paper describes a new idea of thescheduling for MGL, compatible requests first (CRF). Combining the new idea with SQS and DQS,we propose two new scheduling algorithms called CRFS and CRFD. After describing the simulationmodel, this paper illustrates the comparisons of the performance among these four algorithms. Asshown in the experiments, DQS has better performance than SQS, CRFD is better than DQS, CRFSperforms better than SQS, and CRFS is the best one of these four scheduling algorithms. | Qin Xiao & Pang Liping(Department of Computer Science, Huazhong University of Science and Technology,Wuhan 430074, P. R. China) | 1998 | Journal of Systems Engineering and Electronics1998，9，4： | 0 |
| 7 | Weak Serializable Concurrency Control in Real-time Broadcast Environments显示文摘Given the asymmetric communication capabilities in mobile real time environments, traditional serializability based approaches are too restrictive, unnecessary, and impractical. Thus propose the use of a new weaker correctness criterion is proposed. This paper first formally defines the new notion of correctness called weak serializability. After the necessary and sufficient conditions for weak serializability are shown, corresponding concurrency control protocol based on this criterion is outlined for real time broadcast environments. Finally, the simulation results confirmed that the proposed techniques help mobile transactions to meet their deadlines and improve query response time. | 刘云生 Dang Depeng | 2002 | High Technology Letters2002，8，4： | 0 |
| 8 | 三角形中三线共点的求证方法新探 | 魏致远 | 2018 | 好家长(创新教育)2018，0，32： | 0 |
| 9 | Optimistic Transaction Processing in Deterministic Database显示文摘Deterministic databases can improve the performance of distributed workload by eliminating the distributed commit protocol and reducing the contention cost.Unfortunately,the current deterministic scheme does not consider the performance scalability within a single machine.In this paper,we describe a scalable deterministic concurrency control,Deterministic and Optimistic Concurrency Control(DOCC),which is able to scale the performance both within a single node and across multiple nodes.The performance improvement comes from enforcing the determinism lazily and avoiding read-only transaction blocking the execution.The evaluation shows that DOCC achieves 8x performance improvement than the popular deterministic database system,Calvin. | Zhi-Yuan Dong Chu-Zhe Tang Jia-Chen Wang Zhao-Guo Wang Hai-Bo Chen Bin-Yu Zang | 2020 | Journal of Computer Science & Technology2020，35，2： | 0 |
| 10 | Labeled Network Stack: A High-Concurrency and Low-Tail Latency Cloud Server Framework for Massive IoT Devices显示文摘Internet of Things(IoT)applications have massive client connections to cloud servers,and the number of networked IoT devices is remarkably increasing.IoT services require both low-tail latency and high concurrency in datacenters.This study aims to determine whether an order of magnitude improvement is possible in tail latency and concurrency in mainstream systems by proposing a hardware-software codesigned labeled network stack(LNS)for future datacenters.The key innovation is a cross-layered payload labeling mechanism that distinguishes different requests by payload across the full network stack,including application,TCP/IP,and Ethernet layers.This type of design enables prioritized data packet processing and forwarding along the full datapath,such that latency-insensitive requests cannot significantly interfere with high-priority requests.We build a prototype datacenter server to evaluate the LNS design against a commercial X86 server and the mTCP research,using a cloud-supported IoT application scenario.Experimental results show that the LNS design can provide an order of magnitude improvement in tail latency and concurrency.A single datacenter server node can support over 2 million concurrent long-living connections for IoT devices as a 99-percentile tail latency of 50 ms is maintained.In addition,the hardware-software codesign approach remarkably reduces the labeling and prioritization overhead and constrains the interference of high-priority requests to low-priority requests. | Wen-Li Zhang Ke Liu Yi-Fan Shen Ya-Zhu Lan Hui Song Ming-Yu Chen Yuan-Fei Chen | 2020 | Journal of Computer Science & Technology2020，35，1： | 0 |
| 11 | TRANSACTION MANAGEMENT IN DISTRIBUTED DATABASE SYSTEM C-POREL显示文摘This paper covers the transaction management of C-POREL, i. e. the distributed rela-tional data base management system on a microcomputer network. Presented in the pa-per are the concurrency control strategy of transactions in C-POREL, the mechanism ofthe local and global recovery, the reliable state control protocol RSC for getting the ro-bustness of the network and the protocol for processing distributed multisite transactions,and the outline of the architecture of the transaction manager TM of C-POREL. | 周龙骧 | 1989 | Science China Mathematics1989，32，2： | 0 |
| 12 | Study on Agent Based Methods for Concurrency Control in CSCW显示文摘Concurrency control is a critical technology and one of the problems in CSCW systems. With the development of agent based technology, it has also been applied to research and development of CSCW systems. An Agent based method for concurrency control in CSCW is explored in this paper. This new way is achieved by making use of the thoughts of AOP (Agent Oriented Programming) to improve traditional locking method, on the basis of researching characteristics and functional requirements of concurrency control in CSCW, and analyzing various usually used concurrency control methods. All amendments to locking method are done on the basis of the analysis of limitations brought by locking. In this paper, a new algorithm supporting queue of locking request for Agent based concurrency control is also presented. All above aspects are discussed in some detail in this paper. | Li Hu, Yao Shu zhen, Liu Chang hui Department of Computer Science, Beijing University of Aeronautics and Astronautics, Beijing 100083, China | 2001 | Wuhan University Journal of Natural Sciences2001，6，Z1： | 0 |
| 13 | Petri nets semantics ofπ-calculus显示文摘As π-calculus based on the interleaving semantics cannot depict the true concurrency and has few supporting tools,it is translated into Petri nets.π-calculus is divided into basic elements,sequence,concurrency,choice and recursive modules.These modules are translated into Petri nets to construct a complicated system.Petri nets semantics for π-calculus visualize system structure as well as system behaviors.The structural analysis techniques allow direct qualitative analysis of the system properties on the structure of the nets.Finally,Petri nets semantics for π-calculus are illustrated by applying them to mobile telephone systems. | Zhenhua YU Yuanli CAI Haiping XU | 2008 | Frontiers of Electrical and Electronic Engineering in China2008，3，3： | 0 |
| 14 | Supervisory control of concurrent discrete-event systems显示文摘Concurrency is a common feature in most industrial systems,where several components can execute different actions simultaneously.In this paper,we first introduce a new feasible nonblocking concurrent supervisory control map for a concurrent system,and subsequently,new concepts of concurrent controllability and concurrent observability.Then we present a sufficient and necessary condition for the existence of a feasible nonblocking concurrent supervisory controlmap to achieve a given concurrent language.After introducing a new concept of prefix-closed concurrent normality,we show that the supremal concurrently controllable and prefix-closed concurrently normal sublanguages exist and are computable.Our emphasis here is not to address the computational efficiency of solving concurrent supervisory control problems,which is still a technical challenge,but to show that the commonly used Ramadge–Wonham asynchronous control is simply a special case of our proposed concurrent control framework by providing an insightful treatment on compound events. | R.Su | 2015 | Journal of Control and Decision2015，2，2： | 0 |
| 15 | Urban Growth Management through Travel Demand Modeling in Washington and Oregon显示文摘Among the fast growing states in the USA,the States of Washington and Oregon have enacted legislative land use and transportation concurrency/balancing planning policies for orderly urban growth management since 1990 and 1991,respectively.Regional or urban travel demand forecasting models play an instrumental role in implementing the Washington GMA(Growth Management Act)and the Oregon TPR(Transportation Planning Rule).Both program-and project-level modeling approaches to urban land use/transportation system management are evaluated through the selected cities in Washington and Oregon. | Jinxiang Ren | 2018 | Journal of Traffic and Transportation Engineering2018，6，6： | 0 |
| 16 | Remaining Time Prediction for Business Processes with Concurrency Based on Log Representation显示文摘Remaining time prediction of business processes plays an important role in resource scheduling and plan making.The structural features of single process instance and the concurrent running of multiple process instances are the main factors that affect the accuracy of the remaining time prediction.Existing prediction methods does not take full advantage of these two aspects into consideration.To address this issue,a new prediction method based on trace representation is proposed.More specifically,we first associate the prefix set generated by the event log to different states of the transition system,and encode the structural features of the prefixes in the state.Then,an annotation containing the feature representation for the prefix and the corresponding remaining time are added to each state to obtain an extended transition system.Next,states in the extended transition system are partitioned by the different lengths of the states,which considers concurrency among multiple process instances.Finally,the long short-term memory(LSTM)deep recurrent neural networks are applied to each partition for predicting the remaining time of new running instances.By extensive experimental evaluation using synthetic event logs and reallife event logs,we show that the proposed method outperforms existing baseline methods. | Rui Cao Weijian Ni Qingtian Zeng Faming Lu Cong Liu Hua Duan | 2021 | China Communications2021，18，11： | 0 |
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