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parallel skyline queries over uncertain data streams in cloud computing environments

INTERNATIONAL JOURNAL OF WEB AND GRID SERVICES 2014年第1期10卷 24-53页

作者： Li, Xiaoyong Wang, Yijie Li, Xiaoling Wang, Yuan Natl Univ Def Technol Sch Comp Natl Key Lab Parallel & Distributed Proc Changsha 410073 Hunan Peoples R China

Skyline query processing over uncertain data streams has attracted considerable attention recently, due to its importance in helping users make intelligent decisions on complex data. Nevertheless, existing studies only focus on retrieving the skylines over data streams in a centralised environment typically with one processor, which limits the scalability and cannot meet the requirement for massive data analysis. Cloud computing provides unprecedentedly opportunities for supporting massive data management, which can be well adapted to the parallel skyline queries. In this paper, we extensively study the parallel skyline query problem over uncertain data streams in cloud computing environments. Particularly, three parallel models SPM, APM, and DPM are proposed to address the problem based on the sliding window partitioning. Additionally, an adaptive sliding granularity adjustment strategy and a load balance strategy are proposed to further optimise the queries. Extensive experiments are conducted to demonstrate the effectiveness and efficiency of the proposals.

关键词： uncertain data data streams skyline query parallel model cloud computing data management

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Resource allocation with multi-factor node ranking in data center networks

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FUTURE GENERATION COMPUTER SYSTEMS-THE INTERNATIONAL JOURNAL OF ESCIENCE 2014年第1期32卷 1-12页

作者： Li, Xiaoling Wang, Huaimin Ding, Bo Li, Xiaoyong Feng, Dawei Natl Univ Def Technol Coll Comp Natl Key Lab Parallel & Distributed Proc Changsha 410073 Hunan Peoples R China

In data center networks, resource allocation refers to mapping a large number of workloads to substrate networks. Existing heuristic mapping algorithms evaluate the resources of the nodes according to one resource factor or a product of resource factors, which will probably lead to an imbalance of the resource allocation. Furthermore, neglecting the hops of the substrate paths in the resource allocation may result in low resource utilization. In this paper, we adopt a top-k dominating model to rank the nodes, aiming at balancing these factors to improve resource allocation. Moreover, we propose a novel mapping algorithm TK-Match, which consists of a node mapping stage and link mapping stage. In the node mapping stage, TK-Match maps the virtual nodes to the substrate nodes in terms of the node ranking and the hops of the substrate paths. In the link mapping stage, TK-Match adopts the k-shortest path algorithm to map the virtual links. Extensive simulation experiments show that TK-Match can greatly increase the long-term average revenue and the acceptance ratio. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.

关键词： Resource allocation Data center network Workload Substrate network Top-k dominating

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A Contract-based Approach to Specifying and Verifying Safety Critical Systems

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ELECTRONIC NOTES IN THEORETICAL COMPUTER SCIENCE 2007年第2期176卷 89-103页

作者： Dong, Wei Chen, Zhenbang Wang, Ji Natl Lab Parallel & Distributed Proc Changsha Hunan Peoples R China

Light-weight formal method has been regarded as an important approach to development of component-based safety critical systems. The paper proposes an approach which can formally specify and verify the contract of static structure, dynamic behavior and refinement of component systems based on UML 2.0 superstructure. As results, the correctness of static contract can be obtained via type checking of interfaces and connectors. Dynamic contract can be verified through determining the cooperativeness of integrated components, whose contracts are depicted with interface protocol state machines and their semantics models, namely contract automata. The refinement relation between high level component and its implementation will be guaranteed through defining the alternating simulation between contract automata of components at different levels.

关键词： formal specification software verification component-based software development

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Efficient in-place update with grouped and pipelined data transmission in erasure-coded storage systems

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FUTURE GENERATION COMPUTER SYSTEMS-THE INTERNATIONAL JOURNAL OF ESCIENCE 2017年 69卷 24-40页

作者： Pei, Xiaoqiang Wang, Yijie Ma, Xingkong Xu, Fangliang Natl Univ Def Technol Natl Key Lab Parallel & Distributed Proc Coll Comp Changsha 410073 Hunan Peoples R China

distributed storage systems usually adopt erasure coding to achieve better tradeoff between the space efficiency and the data reliability. In-place updates are often used to overwrite the existing data rather than append the new data so as to ensure the data access efficiency. However, existing in-place update approaches either introduce significant I/O overhead or cause low update efficiency in erasure-coded storage systems due to the consistent update of parity blocks. In this paper, we propose a grouped and pipelined update scheme based on erasure codes, called Group-U, which comprises four key design features. (1) It groups the data nodes to complete the data transmission and dynamically adjusts the group size according to the update workload. (2) It pipelines the data transmission and distributes the update computation to all the participating nodes to improve the update efficiency. (3) It adopts the in-time update for data nodes and lazy-update for parity nodes to further reduce the update overhead. (4) It adjusts the occasion triggering the update to be compatible with the node failure. We design and implement Group-U on our Raid distributed Storage System (RDFS) and conduct testbed experiments on different update schemes under various parameter settings. The analysis and experimental results show that Group-U consumes 22% increase of update overhead compared with PUM and achieves 46% reduction of update overhead compared with PDP-P and PUS. Furthermore, Group-U achieves 69%, 34% and 21% reduction of update time on average compared with PUM, PDP-P and PUS respectively. (C) 2016 Elsevier B.V. All rights reserved.

关键词： In-place Update Grouping In-time Lazy-update

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TA-Update: An Adaptive Update Scheme with Tree-Structured Transmission in Erasure-Coded Storage Systems

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IEEE TRANSACTIONS ON parallel AND distributed SYSTEMS 2018年第8期29卷 1893-1906页

作者： Wang, Yijie Pei, Xiaoqiang Ma, Xingkong Xu, Fangliang Natl Univ Def Technol Coll Comp Natl Key Lab Parallel & Distributed Proc Changsha 410073 Hunan Peoples R China

Erasure coding has received considerable attentions due to the better tradeoff between the space efficiency and reliability. The frequent update of the stored data in the distributed storage systems has posed a new challenge for erasure codes: how to update the erasure-coded data in a general, efficient and adaptive way. However, existing update schemes of erasure codes are inadequate to meet these requirements, since their code-related update manners lead to a low generality, their star-structured data transmission manners lead to a low update efficiency, and their redo manners when encountering the node failure lead to a low adaptivity. In this paper, we propose an adaptive update scheme with the tree-structured transmission, called TA-Update, which consists of a code-independent update framework and three algorithms: the rack-aware tree construction algorithm, the top-down data processing algorithm and the rollback-based failure processing algorithm. For generality, we propose a code-independent update framework with the tree structure to support the MDS code with any coding parameter. For efficiency, a rack-aware tree construction algorithm is proposed to achieve the high available bandwidth, which organizes the data node and parity nodes as an update tree. Moreover, a top-down data processing algorithm is proposed to achieve the high transmission and computation efficiency, which pipelines the data transmission along the update tree and distributes the encoding computations among all the participating nodes. For adaptivity, we propose a rollback-based failure processing algorithm to achieve high adaptivity, which handles the node failure during update with the existing update tree in a rollback manner. To evaluate the performance of TA-Update, we conduct experiments on HDFS-RAID under various parameter settings on both 30 physical and 200 virtual machines. Extensive experiments confirm that TA-Update could support the various erasure codes with any parameter, i

关键词： distributed storage system data update update tree erasure codes

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A survey of queries over uncertain data

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KNOWLEDGE AND INFORMATION SYSTEMS 2013年第3期37卷 485-530页

作者： Wang, Yijie Li, Xiaoyong Li, Xiaoling Wang, Yuan Natl Univ Def Technol Sch Comp Natl Key Lab Parallel & Distributed Proc Changsha 410073 Hunan Peoples R China

Uncertain data have already widely existed in many practical applications recently, such as sensor networks, RFID networks, location-based services, and mobile object management. Query processing over uncertain data as an important aspect of uncertain data management has received increasing attention in the field of database. Uncertain query processing poses inherent challenges and demands non-traditional techniques, due to the data uncertainty. This paper surveys this interesting and still evolving research area in current database community, so that readers can easily obtain an overview of the state-of-the-art techniques. We first provide an overview of data uncertainty, including uncertainty types, probability representation models, and sources of probabilities. We next outline the current major types of uncertain queries and summarize the main features of uncertain queries. Particularly, we present and analyze several typical uncertain queries in detail, such as skyline queries, top- queries, nearest-neighbor queries, aggregate queries, join queries, range queries, and threshold queries over uncertain data. Finally, we present many interesting research topics on uncertain queries that have not yet been explored.

关键词： Uncertain data Uncertain queries Skyline query Top-k query Nearest-neighbor query Aggregate query

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QR decomposition architecture using the iteration look-ahead modified Gram-Schmidt algorithm

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IET CIRCUITS DEVICES & SYSTEMS 2016年第5期10卷 402-409页

作者： Liu, Cang Tang, Chuan Yuan, Luechao Xing, Zuocheng Zhang, Yang Natl Univ Def Technol Natl Lab Parallel & Distributed Proc Changsha Hunan Peoples R China

QR decomposition is extensively adopted in multiple-input-multiple-output orthogonal frequency-division multiplexing wireless communication systems, and is one of the performance bottlenecks in lots of high-performance wireless communication algorithms. To implement low processing latency QR decomposition with hardware, the authors propose a novel iterative look-ahead modified Gram-Schmidt (ILMGS) algorithm based on the traditional modified Gram-Schmidt (MGS) algorithm. They also design the corresponding triangular systolic array (TSA) architecture with the proposed ILMGS algorithm, which only needs n time slots for a n x n real matrix. For reducing the hardware overhead, they modify the TSA architecture into an iterative architecture. They also design a modified iterative architecture to further reduce the hardware overhead. The implementation results show that the normalised processing latency of the modified iterative architecture based on the proposed ILMGS algorithm is 1.36 times lower than the one based on the MGS algorithm. To the best of the authors' knowledge, the designed architecture achieves the superior latency performance than the existing works.

关键词： MIMO communication wireless channels iterative methods QR decomposition architecture wireless communication algorithms multiple-input-multiple-output orthogonal frequency-division multiplexing iterative look-ahead modified Gram-Schmidt algorithm modified Gram-Schmidt algorithm triangular systolic array

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Repairing multiple failures adaptively with erasure codes in distributed storage systems

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CONCURRENCY AND COMPUTATION-PRACTICE & EXPERIENCE 2016年第5期28卷 1437-1461页

作者： Pei, Xiaoqiang Wang, Yijie Ma, Xingkong Xu, Fangliang Natl Univ Def Technol Coll Comp Natl Key Lab Parallel & Distributed Proc Changsha 410073 Hunan Peoples R China

Repairs of multiple failures in distributed storage systems have posed the challenges for erasure coding: how to minimize the repair time with the least extra repair network traffic cost. However, existing repair schemes designed for single failure suffer from the high network traffic cost due to the serial repairs for multiple failures. Repair schemes designed for multiple failures suffer from long repair time due to the centralized repair structure. In this paper, we propose a decentralized adaptive repair scheme, called DARS, to minimize the repair time with the least extra network traffic cost. Specially, we propose a three-layer repair model to support the repairs for both the single and multiple failures. For low repair time, a bandwidth-aware node selection technique is proposed to guide the selection of nodes, and a line-structured data transmission technique is proposed to organize the data transmission between the providers and the newcomer. For the least extra network traffic cost, a core-based data distribution technique is proposed to organize the data transmission between the coordinator and other newcomers, and an intersection provider adjustment technique is proposed to adaptively adjust the number of intersection providers. Moreover, we adopt the lazy repair' within a stripe to further reduce the repair network traffic cost. We implement and evaluate DARS on our raid distributed storage system under various parameter settings with 30 physical machines and 200 virtual machines. Experimental results confirm that DARS reduces the repair time by 29% and 55% on average compared with tree-structured repair and CORE, respectively. Copyright (c) 2015 John Wiley & Sons, Ltd.

关键词： Repair Wound Healing traffic network Cache Memory System data transmission TIME TO REPAIR telecommunication traffic DARS gene multiple fault parameter setting

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An Area-Efficient Hybrid Polar Decoder With Pipelined Architecture

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IEEE ACCESS 2020年 8卷 68068-68082页

作者： Wang, Yu Wang, Qinglin Zhang, Yang Qiu, Shikai Xing, Zuocheng Natl Univ Def Technol Natl Lab Parallel & Distributed Proc Changsha 410073 Peoples R China

As the first kind of capacity-achieving forward error correction (FEC) codes, polar codes have attracted much research interest recently. Compared with traditional FEC codes, polar codes show better error correction performance when successive cancellation list (SCL) decoding with cyclic redundancy check is adopted. However, its serial decoding nature and high complexity of list management lead to its low throughput. Though the adaptive SCL decoding and hybrid decoding can improve the throughput, it comes at cost of implementation area. In this paper, we propose a pipelined hybrid decoding procedure and the corresponding hardware architecture to improve the area efficiency. In our design, the idle decoding cores are employed for successive cancellation (SC) decoding when SCL decoding is not working. The SCL decoding will be activated when the SC decoding fails. Different decoding cores work according to their own operation sequences and share one common processing array to improve the utilization ratio of processing elements. Constant receiving interval is supported with the design of input buffer to store all received codewords. A software platform is established to optimize the design parameters for each module of decoder. Moreover, the corresponding architecture is implemented using 65nm technology. Experimental results show that the proposed decoder can achieve a similar error correction performance with the SCL decoding with list size 16. Compared to the state-of-the-art available hybrid decoder, our proposed pipelined hybrid decoder is 3.07 x more area efficient.

关键词： Polar decoder hybrid decoding pipelined architecture area-efficient

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Scalable and elastic event matching for attribute-based publish/subscribe systems

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FUTURE GENERATION COMPUTER SYSTEMS-THE INTERNATIONAL JOURNAL OF ESCIENCE 2014年 36卷 102-119页

作者： Ma, Xingkong Wang, Yijie Qiu, Qing Sun, Weidong Pei, Xiaoqiang Natl Univ Def Technol Sch Comp Natl Key Lab Parallel & Distributed Proc Changsha 410073 Hunan Peoples R China

Due to the sudden change of the arrival live content rate and the skewness of the large-scale subscriptions, the rapid growth of emergency applications presents a new challenge to the current publish/subscribe systems: providing a scalable and elastic event matching service. However, most existing event matching services cannot adapt to the sudden change of the arrival live content rate, and generate a non-uniform distribution of load on the servers because of the skewness of the large-scale subscriptions. To this end, we propose SEMAS, a scalable and elastic event matching service for attribute-based pub/sub systems in the cloud computing environment. SEMAS uses one-hop lookup overlay to reduce the routing latency. Through a hierarchical multi-attribute space partition technique, SEMAS adaptively partitions the skewed subscriptions and maps them into balanced clusters to achieve high matching throughput. The performance-aware detection scheme in SEMAS adaptively adjusts the scale of servers according to the churn of workloads, leading to high performance-price ratio. A prototype system on an OpenStack-based platform demonstrates that SEMAS has a linear increasing matching capacity as the number of servers and the partitioning granularity increase. It is able to elastically adjust the scale of servers and tolerate a large number of server failures with low latency and traffic overhead. Compared with existing cloud based pub/sub systems, SEMAS achieves higher throughput in various workloads. (C) 2013 Elsevier B.V. All rights reserved.

关键词： Publish/subscribe Attribute-based Event matching Content space partitioning Cloud computing

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