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Parallel and Distributed Systems, IEEE Transactions on

Issue 7 • Date July 2012

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Displaying Results 1 - 23 of 23
  • [Front cover]

    Page(s): c1
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  • [Inside front cover]

    Page(s): c2
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  • Distributed Evidence Propagation in Junction Trees on Clusters

    Page(s): 1169 - 1177
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    Evidence propagation is a major step in exact inference, a key problem in exploring probabilistic graphical models. In this paper, we propose a novel approach for parallelizing evidence propagation in junction trees on clusters. Our proposed method explores structural parallelism in a given junction tree. We decompose a junction tree into a set of subtrees, each consisting of one or multiple leaf-root paths in the junction tree. In evidence propagation, we first perform evidence collection in these subtrees concurrently. Then, the partially updated subtrees exchange data for junction tree merging, so that all the cliques in the junction tree can be fully updated for evidence collection. Finally, evidence distribution is performed in all the subtrees to complete evidence propagation. Since merging subtrees requires communication across processors, we propose a technique called bitmap partitioning to explore the tradeoff between bandwidth utilization efficiency and the overhead due to the startup latency of message passing. We implemented the proposed method using Message Passing Interface (MPI) on a state-of-the-art Myrinet cluster consisting of 128 processors. Compared with a baseline method, our technique results in improved scalability. View full abstract»

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  • Distributed Packet Buffers for High-Bandwidth Switches and Routers

    Page(s): 1178 - 1192
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    High-speed routers rely on well-designed packet buffers that support multiple queues, provide large capacity and short response times. Some researchers suggested combined SRAM/DRAM hierarchical buffer architectures to meet these challenges. However, these architectures suffer from either large SRAM requirement or high time-complexity in the memory management. In this paper, we present scalable, efficient, and novel distributed packet buffer architecture. Two fundamental issues need to be addressed to make this architecture feasible: 1) how to minimize the overhead of an individual packet buffer; and 2) how to design scalable packet buffers using independent buffer subsystems. We address these issues by first designing an efficient compact buffer that reduces the SRAM size requirement by (k-1)/k. Then, we introduce a feasible way of coordinating multiple subsystems with a load-balancing algorithm that maximizes the overall system performance. Both theoretical analysis and experimental results demonstrate that our load-balancing algorithm and the distributed packet buffer architecture can easily scale to meet the buffering needs of high bandwidth links and satisfy the requirements of scale and support for multiple queues. View full abstract»

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  • DRAGON: Detection and Tracking of Dynamic Amorphous Events in Wireless Sensor Networks

    Page(s): 1193 - 1204
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    Wireless sensor networks may be deployed in many applications to detect and track events of interest. Events can be either point events with an exact location and constant shape, or region events which cover a large area and have dynamic shapes. While both types of events have received attention, no event detection and tracking protocol in existing wireless sensor network research is able to identify and track region events with dynamic identities, which arise when events are created or destroyed through splitting and merging. In this paper, we propose DRAGON, an event detection and tracking protocol which is able to handle all types of events including region events with dynamic identities. DRAGON employs two physics metaphors: event center of mass, to give an approximate location to the event; and node momentum, to guide the detection of event merges and splits. Both detailed theoretical analysis and extensive performance studies of DRAGON's properties demonstrate that DRAGON's execution is distributed among the sensor nodes, has low latency, is energy efficient, is able to run on a wide array of physical deployments, and has performance which scales well with event size, speed, and count. View full abstract»

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  • Embedded Transitive Closure Network for Runtime Deadlock Detection in Networks-on-Chip

    Page(s): 1205 - 1215
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    Interconnection networks with adaptive routing are susceptible to deadlock, which could lead to performance degradation or system failure. Detecting deadlocks at runtime is challenging because of their highly distributed characteristics. In this paper, we present a deadlock detection method that utilizes runtime transitive closure (TC) computation to discover the existence of deadlock-equivalence sets, which imply loops of requests in networks-on-chip (NoCs). This detection scheme guarantees the discovery of all true deadlocks without false alarms in contrast with state-of-the-art approximation and heuristic approaches. A distributed TC-network architecture, which couples with the NoC infrastructure, is also presented to realize the detection mechanism efficiently. Detailed hardware realization architectures and schematics are also discussed. Our results based on a cycle-accurate simulator demonstrate the effectiveness of the proposed method. It drastically outperforms timing-based deadlock detection mechanisms by eliminating false detections and, thus, reducing energy wastage in retransmission for various traffic scenarios including real-world application. We found that timing-based methods may produce two orders of magnitude more deadlock alarms than the TC-network method. Moreover, the implementations presented in this paper demonstrate that the hardware overhead of TC-networks is insignificant. View full abstract»

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  • Exploring Peer-to-Peer Locality in Multiple Torrent Environment

    Page(s): 1216 - 1226
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    The fast-growing traffic of Peer-to-Peer (P2P) applications, most notably BitTorrent (BT), is putting unprecedented pressure to Internet Service Providers (ISPs). P2P locality has, therefore, been widely suggested to mitigate the costly inter-ISP traffic. In this paper, we for the first time examine the existence and distribution of the locality through a large-scale hybrid PlanetLab-Internet measurement. We find that even in the most popular Autonomous Systems (ASes), very few individual torrents are able to form large enough local clusters of peers, making state-of-the-art locality mechanisms for individual torrents quite inefficient. Inspired by peers' multiple torrent behavior, we develop a novel framework that traces and recovers the available contents at peers across multiple torrents, and thus effectively amplifies the possibilities of local sharing. We address the key design issues in this framework, in particular, the detection of peer migration across the torrents. We develop a smart detection mechanism with shared trackers, which achieves 45 percent success rate without any tracker-level communication overhead. We further demonstrate strong evidence that the migrations are not random, but follow certain patterns with correlations. This leads to torrent clustering, a practical enhancement that can increase the detection rate to 75 percent, thus greatly facilitating locality across multiple torrents. The simulation results indicate that our framework can successfully reduce the cross-ISP traffic and minimize the possible degradation of peers' downloading experiences. View full abstract»

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  • Flash Crowd in P2P Live Streaming Systems: Fundamental Characteristics and Design Implications

    Page(s): 1227 - 1239
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    Peer-to-peer (P2P) live video streaming systems have recently received substantial attention, with commercial deployment gaining increased popularity in the internet. It is evident from our practical experiences with real-world systems that, it is not uncommon for hundreds of thousands of users to choose to join a program in the first few minutes of a live broadcast. Such a severe flash crowd phenomenon in live streaming poses significant challenges in the system design. In this paper, for the first time, we develop a mathematical model to: 1) capture the fundamental relationship between time and scale in P2P live streaming systems under a flash crowd, and 2) explore the design principle of population control to alleviate the impact of the flash crowd. We carry out rigorous analysis that brings forth an in-depth understanding on effects of the gossip protocol and peer dynamics. In particular, we demonstrate that there exists an upper bound on the system scale with respect to a time constraint. By trading peer startup delays in the initial stage of a flash crowd for system scale, we design a simple and flexible population control framework that can alleviate the flash crowd without the requirement of otherwise costly server deployment. View full abstract»

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  • Formal Semantics, Compilation and Execution of the GALS Programming Language DSystemJ

    Page(s): 1240 - 1254
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    The paper presents a programming language, DSystemJ, for dynamic distributed Globally Asynchronous Locally Synchronous (GALS) systems, its formal model of computation, formal syntax and semantics, its compilation and implementation. The language is aimed at dynamic distributed systems, which use socket based communication protocols for communicating between components. DSystemJ allows the creation and control at runtime of asynchronous processes called clock-domains, their mobility on a distributed execution platform, as well as the runtime reconfiguration of the system's functionality and topology. As DSystemJ is based on a GALS model of computation and has a formal semantics, it offers very safe mechanisms for implementation of distributed systems, as well as potential for their formal verification. The details and principles of its compilation, as well as its required runtime support are described. The runtime support is implemented in the SystemJ GALS language that can be considered as a static subset of DSystemJ. View full abstract»

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  • Large-Scale Transient Stability Simulation of Electrical Power Systems on Parallel GPUs

    Page(s): 1255 - 1266
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    This paper proposes large-scale transient stability simulation based on the massively parallel architecture of multiple graphics processing units (GPUs). A robust and efficient instantaneous relaxation (IR)-based parallel processing technique which features implicit integration, full Newton iteration, and sparse LU-based linear solver is used to run the multiple GPUs simultaneously. This implementation highlights the combination of coarse-grained algorithm-level parallelism with fine-grained data-parallelism of the GPUs to accelerate large-scale transient stability simulation. Multithreaded parallel programming makes the entire implementation highly transparent, scalable, and efficient. Several large test systems are used for the simulation with a maximum size of 9,984 buses and 2,560 synchronous generators all modeled in detail resulting in matrices that are larger than 20, 000 × 20, 000. View full abstract»

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  • On the Design and Deployment of RFID Assisted Navigation Systems for VANETs

    Page(s): 1267 - 1274
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    In this paper, we propose a systematic approach to designing and deploying a RFID Assisted Navigation System (RFID-ANS) for VANETs. RFID-ANS consists of passive tags deployed on roads to provide navigation information while the RFID readers attached to the center of the vehicle bumper query the tag when passing by to obtain the data for navigation guidance. We analyze the design criteria of RFID-ANS and present the design of the RFID reader in detail to support vehicles at high speeds. We also jointly consider the scheduling of the read attempts and the deployment of RFID tags based on the navigation requirements to support seamless navigations. The estimation of the vehicle position and its accuracy are also investigated. View full abstract»

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  • On the Hop Count Statistics in Wireless Multihop Networks Subject to Fading

    Page(s): 1275 - 1287
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    Consider a wireless multihop network where nodes are randomly distributed in a given area following a homogeneous Poisson process. The hop count statistics, viz. the probabilities related to the number of hops between two nodes, are important for performance analysis of the multihop networks. In this paper, we provide analytical results on the probability that two nodes separated by a known euclidean distance are k hops apart in networks subject to both shadowing and small-scale fading. Some interesting results are derived which have generic significance. For example, it is shown that the locations of nodes three or more hops away provide little information in determining the relationship of a node with other nodes in the network. This observation is useful for the design of distributed routing, localization, and network security algorithms. As an illustration of the application of our results, we derive the effective energy consumption per successfully transmitted packet in end-to-end packet transmissions. We show that there exists an optimum transmission range which minimizes the effective energy consumption. The results provide useful guidelines on the design of a randomly deployed network in a more realistic radio environment. View full abstract»

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  • Performance and Reliability of Non-Markovian Heterogeneous Distributed Computing Systems

    Page(s): 1288 - 1301
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    Average service time, quality-of-service (QoS), and service reliability associated with heterogeneous parallel and distributed computing systems (DCSs) are analytically characterized in a realistic setting for which tangible, stochastic communication delays are present with nonexponential distributions. The departure from the traditionally assumed exponential distributions for event times, such as task-execution times, communication arrival times and load-transfer delays, gives rise to a non-Markovian dynamical problem for which a novel age dependent, renewal-based distributed queuing model is developed. Numerical examples offered by the model shed light on the operational and system settings for which the Markovian setting, resulting from employing an exponential-distribution assumption on the event times, yields inaccurate predictions. A key benefit of the model is that it offers a rigorous framework for devising optimal dynamic task reallocation (DTR) policies systematically in heterogeneous DCSs by optimally selecting the fraction of the excess loads that need to be exchanged among the servers, thereby controlling the degree of cooperative processing in a DCSs. Key results on performance prediction and optimization of DCSs are validated using Monte-Carlo (MC) simulation as well as experiments on a distributed computing testbed. The scalability, in the number of servers, of the age-dependent model is studied and a linearly scalable analytical approximation is derived. View full abstract»

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  • Quantitative Measurement and Design of Source-Location Privacy Schemes for Wireless Sensor Networks

    Page(s): 1302 - 1311
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    Wireless sensor networks (WSNs) have been widely used in many areas for critical infrastructure monitoring and information collection. While confidentiality of the message can be ensured through content encryption, it is much more difficult to adequately address source-location privacy (SLP). For WSNs, SLP service is further complicated by the nature that the sensor nodes generally consist of low-cost and low-power radio devices. Computationally intensive cryptographic algorithms (such as public-key cryptosystems), and large scale broadcasting-based protocols may not be suitable. In this paper, we first propose criteria to quantitatively measure source-location information leakage in routing-based SLP protection schemes for WSNs. Through this model, we identify vulnerabilities of some well-known SLP protection schemes. We then propose a scheme to provide SLP through routing to a randomly selected intermediate node (RSIN) and a network mixing ring (NMR). Our security analysis, based on the proposed criteria, shows that the proposed scheme can provide excellent SLP. The comprehensive simulation results demonstrate that the proposed scheme is very efficient and can achieve a high message delivery ratio. We believe it can be used in many practical applications. View full abstract»

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  • Relaxed Concurrency Control in Software Transactional Memory

    Page(s): 1312 - 1325
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    Some of today's TM systems implement the two-phase-locking (2PL) algorithm which aborts transactions every time a conflict occurs. 2PL is a simple algorithm that provides fast transactional operations. However, it limits concurrency in benchmarks with high contention because it increases the rate of aborts. We propose the use of a more relaxed concurrency control algorithm to provide better concurrency. This algorithm is based on the conflict-serializability (CS) model. Unlike 2PL, it allows some transactions to commit successfully even when they make conflicting accesses. We implement this algorithm in a STM system and evaluate its performance on 16 cores using standard benchmarks. Our evaluation shows that the algorithm improves the performance of applications with long transactions and high abort rates. Throughput is improved by up to 2.99 times despite the overheads of testing for CS at runtime. These improvements come with little additional implementation complexity and require no changes to the transactional programming model. We also propose an adaptive approach that switches between 2PL and CS to mitigate the overhead in applications that have low abort rates. View full abstract»

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  • Reliable and Energy-Efficient Multipath Communications in Underwater Sensor Networks

    Page(s): 1326 - 1335
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    Weak reliability and low energy efficiency are the inherent problems in Underwater Sensor Networks (USNs) characterized by the acoustic channels. Although multiple-path communications coupled by Forward Error Correction (FEC) can achieve high performance for USNs, the low probability of successful recovery of received packets in the destination node significantly affects the overall Packet Error Rate (PER) and the number of multiple paths required, which in turn becomes a critical factor for reliability and energy consumption. In this paper, a novel Multiple-path FEC approach (M-FEC) based on Hamming Coding is proposed for improving reliability and energy efficiency in USNs. A Markovian model is developed to formulate the probability of M-FEC and calculate the overall PER for the proposed decision and feedback scheme, which can reduce the number of the multiple paths and achieve the desirable overall PER in M-FEC. Compared to the existing multipath communication scheme, extensive simulation experiments show that the proposed approach achieves significantly lower packet delay while consuming only 20-30 percent of energy in multiple-path USNs with various Bit Error Rates (BER). View full abstract»

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  • Ship Detection with Wireless Sensor Networks

    Page(s): 1336 - 1343
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    Surveillance is a critical problem for harbor protection, border control or the security of commercial facilities. The effective protection of vast near-coast sea surfaces and busy harbor areas from intrusions of unauthorized marine vessels, such as pirates smugglers or, illegal fishermen is particularly challenging. In this paper, we present an innovative solution for ship intrusion detection. Equipped with three-axis accelerometer sensors, we deploy an experimental Wireless Sensor Network (WSN) on the sea's surface to detect ships. Using signal processing techniques and cooperative signal processing, we can detect any passing ships by distinguishing the ship-generated waves from the ocean waves. We design a three-tier intrusion detection system with which we propose to exploit spatial and temporal correlations of an intrusion to increase detection reliability. We conduct evaluations with real data collected in our initial experiments, and provide quantitative analysis of the detection system, such as the successful detection ratio, detection latency, and an estimation of an intruding vessel's velocity. View full abstract»

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  • Topology Enhancements in Wireless Multihop Networks: A Top-Down Approach

    Page(s): 1344 - 1357
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    Contemporary traffic demands call for efficient infrastructures capable of sustaining increasing volumes of social communications. In this work, we focus on improving the properties of wireless multihop networks with social features through network evolution. Specifically, we introduce a framework, based on inverse Topology Control (iTC), for distributively modifying the transmission radius of selected nodes, according to social paradigms. Distributed iTC mechanisms are proposed for exploiting evolutionary network churn in the form of edge/node modifications, without significantly impacting available resources. We employ continuum theory for analytically describing the proposed top-down approach of infusing social features in physical topologies. Through simulations, we demonstrate how these mechanisms achieve their goal of reducing the average path length, so as to make a wireless multihop network scale like a social one, while retaining its original multihop character. We study the impact of the proposed topology modifications on the operation and performance of the network with respect to the average throughput, delay, and energy consumption of the induced network. View full abstract»

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  • Take the CS Library wherever you go! [advertisement]

    Page(s): 1358
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    Page(s): 1359
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  • IEEE Computer Society OnlinePlus Tutorial Video

    Page(s): 1360
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  • [Inside back cover]

    Page(s): c3
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  • [Back cover]

    Page(s): c4
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Aims & Scope

IEEE Transactions on Parallel and Distributed Systems (TPDS) is published monthly. It publishes a range of papers, comments on previously published papers, and survey articles that deal with the parallel and distributed systems research areas of current importance to our readers.

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Meet Our Editors

Editor-in-Chief
David Bader
College of Computing
Georgia Institute of Technology