Consistency is an important issue in distributed Shared Memory (DSM) systems. These systems share a set of objects or virtual memory pages. The data sharing enables the applications in workloads to access the data con...
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ISBN:
(纸本)0769523129
Consistency is an important issue in distributed Shared Memory (DSM) systems. These systems share a set of objects or virtual memory pages. The data sharing enables the applications in workloads to access the data concurrently. But, these concurrent accesses can generate some inconsistencies in the shared data state. The consistency models are responsible for managing consistency of shared data for the workloads. In this work, we propose, present and analyze a reconfigurable consistency model for object based DSMs. We called this consistency model ROCoM (Reconfigurable Object Consistency Model). ROCoM behavior was represented using a reconfigurable algorithm (RA) and it analysis was made using a simulation tool (ClusterSim - Cluster Simulation Tool). Our results show that ROCoM, on average, had 55% better performance than the other traditional consistency models.
Many of the world's most critical systems are distributed real-time embedded (ORE) systems, with mission-critical quality of service (QoS) requirements. However, because of their nature - heterogeneous nodes and l...
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ISBN:
(纸本)0769523129
Many of the world's most critical systems are distributed real-time embedded (ORE) systems, with mission-critical quality of service (QoS) requirements. However, because of their nature - heterogeneous nodes and links, shared and constrained resources, and deployment in dynamic environments - providing QoS requires coordinated QoS management throughout the system of multiple end-to-end application streams competing for shared resources. It requires dynamic resource allocation to these end-to-end application streams based on potentially changing mission requirements and shaping application behaviors to effectively use the resources that are allocated. In this paper, we describe the issues involved with providing end-to-end QoS management in DRE systems, an architecture we have designed to support system-wide end-to-end QoS management, and a multi-UAV surveillance and target tracking application we are using to evaluate these technologies.
Sequence comparison is a basic operation in DNA sequencing projects, and most of sequence comparison methods used are based on heuristics, which are faster but there are no guarantees that the best alignments will be ...
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ISBN:
(纸本)0769523129
Sequence comparison is a basic operation in DNA sequencing projects, and most of sequence comparison methods used are based on heuristics, which are faster but there are no guarantees that the best alignments will be produced. On the other hand, the algorithm proposed by Smith-Waterman obtains the best local alignments at the expense of very high computing power and huge memory requirements. In this article, we present and evaluate our experiments with three strategies to run the Smith-Waterman algorithm in a cluster of workstations using a distributed Shared Memory System. Our results on an eight-machine cluster presented very good speedups and indicate that impressive improvements can be achieved, depending on the strategy used. Also, we present some theoretical remarks on how to reduce the amount of memory used.
In thin paper, we present, verify and analyze the performance of JSDESLib (Java Simple Discrete-Event Simulation Library). It is a simplified and easy-to-use Java-based library for the development of discreteevent sim...
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ISBN:
(纸本)0769523129
In thin paper, we present, verify and analyze the performance of JSDESLib (Java Simple Discrete-Event Simulation Library). It is a simplified and easy-to-use Java-based library for the development of discreteevent simulation tools of parallel systems. Our main objectives are: to propose, develop and implement JSDESLib: as a parallel event-oriented simulation library that simplifies the development of simulation tools;with a next earliest event mechanism and communication management between entities. Other main objectives are: to verify and analyze the performance of JSDESLib. A secondary objective is to present some simulation tools that were developed with that library. The main contributions of this work are: the proposal, implementation and performance analysis of JSDESLib;simplicity and ease usage of a parallel-optimized implementation of that library.
At present, saving energy consumption of modern processors and fault tolerance become major concerns due to the fact that high power consumption increases heat dissipation, which leads to decreased reliability of syst...
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ISBN:
(纸本)0769523129
At present, saving energy consumption of modern processors and fault tolerance become major concerns due to the fact that high power consumption increases heat dissipation, which leads to decreased reliability of systems. Similarly, the faults of running tasks also reduce the reliability of systems. The algorithms proposed in this paper are based on the policy of shortest-task-first and combined with other efficient techniques, such as shared slack reclamation and checkpoint. Consequently, not only real-time tasks can be completed before deadline, but also reduction of the global power consumption and fault-tolerance will be satisfied dynamically. In this paper, we present four algorithms to cope with scheduling independent task sets and task sets with precedence relationship in homogeneous and heterogeneous systems, respectively. Moreover, we present dynamic fault-tolerant algorithm. Compared to the efficient algorithms presented so far, our algorithms show lower communicational complexity and much better scheduling performance in terms of makespan and energy consumption.
The next generation of mobile systems with multimedia processing capabilities and wireless connectivity will be increasingly deployed in highly dynamic and distributed environments for multimedia playback and delivery...
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ISBN:
(纸本)0769523129
The next generation of mobile systems with multimedia processing capabilities and wireless connectivity will be increasingly deployed in highly dynamic and distributed environments for multimedia playback and delivery (e.g. video streaming, multimedia conferencing). The challenge is to meet the heavy resource demands of multimedia applications under the stringent energy, computational, and bandwidth constraints of mobile systems, while constantly adapting to the global state changes of the distributed environment. In this paper, we present our initiatives under the FORGE framework to address the issue of delivering high quality multimedia content in mobile environments. In order to cope with the resource intensive nature of multimedia applications and dynamically changing global state (e.g. node mobility, network congestion), an end-to-end approach to QoS aware power optimization is required. We present a framework for coordinating energy optimizing strategies across various layers of system implementation and functionality and discuss techniques that can be employed to achieve energy gains for mobile multimedia systems.
State-space based techniques represent a powerful analysis tool of discrete-event systems. One way to face the state-space explosion is the exploitation of behavioral symmetries of distributed systems. Well-Formed Col...
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ISBN:
(纸本)0769523129
State-space based techniques represent a powerful analysis tool of discrete-event systems. One way to face the state-space explosion is the exploitation of behavioral symmetries of distributed systems. Well-Formed Coloured Petri Nets (WN) allow the direct construction of a symbolic reachability graph (SRG) that captures symmetries suitably encoded in WN syntax. Most real systems however mix symmetric and asymmetric behaviors. The SRG, and more generally, all those approaches based on a static description of symmetries, have shown not to be effective in such cases. In this paper two quotient graphs are proposed as effective analysis frameworks for asymmetric systems. Both rely on WN syntax extended with relational operators. The first one is an extension of the SRG that exploits local symmetries. The second technique uses linear constraints and substate inclusion in order to aggregate states. An asymmetric distributed leader-election algorithm is used as running example.
In recent years, we have seen a dramatic increase in the use of data-centric distributed systems such as global grid infrastructures, sensor networks, network monitoring, and various puhlish-subscribe systems. The rea...
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ISBN:
(纸本)0769523129
In recent years, we have seen a dramatic increase in the use of data-centric distributed systems such as global grid infrastructures, sensor networks, network monitoring, and various puhlish-subscribe systems. The realization of this potential requires adequate support from middleware that could be used to deploy and support such systems. In this regard, we propose an integrated distributed indexing architecture that supports scalable handling of intense dynamic information flows. The architecture is geared towards providing timely responses to queries of different types while minimizing the use of network and computational resources. The underlying communication framework ensures scalability and load balancing of communication as well as adaptivity in presence of dynamic changes. We elaborate on database and content-based routing methodologies used in the integrated solution as well as non-trivial interaction between them, and thereby provide a valuable feedback to the designers of these techniques. We demonstrate the effectiveness of our architecture with performance results that we obtained using our prototype implementation on top of the Chord system simulator.
Network security breaches hinder the application of distributed computing systems manifested as the Grids, clusters, intranets, extranets, or P2P systems. A new integrated approach is presented for building future, ne...
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ISBN:
(纸本)0769523129
Network security breaches hinder the application of distributed computing systems manifested as the Grids, clusters, intranets, extranets, or P2P systems. A new integrated approach is presented for building future, network-based intrusion detection systems (NIDS). We integrate the Snort (a NIDS) with a custom-designed anomaly detection system (ADS) to yield a powerful cyber defense system, called CAIDS. This system detects known attacks through signature matching and reveals network anomalies by Internet traffic datamining. The CAIDS design integrates two different detection engines for alert correlation between intrusions and anomalies. We aim to automate signature generation into Snort database. The system was tested over an Internet trace of 24 millions of packets containing 200 attacks. Our simulation experiments result in a 75% detection rate on all attacks with a low 5% false alarm rate. The system generates alerts on both intrusive attacks to distributed resources and anomalies detected in the Internet, intranet, and extranet connections.
Architectures based on networked servers have become a de-facto standard for distributed Virtual Environment (DVE) systems. These systems allow a large number of remote users to share a single 3D virtual scene. In ord...
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ISBN:
(纸本)0769523129
Architectures based on networked servers have become a de-facto standard for distributed Virtual Environment (DVE) systems. These systems allow a large number of remote users to share a single 3D virtual scene. In order to provide quality of service in a DVE system, clients should be assigned to servers taking into account system throughput and system latency. This highly complex problem is known as the quality of service (QoS) problem. This paper proposes an elitist sexual genetic algorithm for solving the QoS problem in distributed Virtual Environment systems. Performance evaluation results show that, due to its ability of both finding good search paths and keeping diversity escaping from local minima, this nature inspired technique can provide significantly better solutions than other heuristic methods with shorter execution times. Therefore, the proposed implementation of GA search method can improve the QoS offered by DVE systems.
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