We consider a distributed computer system in Wardrop equilibrium, i.e., situations where no user can reduce its own response time by unilaterally choosing another path, if all the other users retain their present path...
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ISBN:
(纸本)0889865701
We consider a distributed computer system in Wardrop equilibrium, i.e., situations where no user can reduce its own response time by unilaterally choosing another path, if all the other users retain their present paths. The Braess paradox is a famous example of paradoxical cases where adding capacity to a network degrades the performance of all users. This study examines numerically some examples around the Braess-like paradox in a distributed computer system. We found that Braess's paradox can occur, namely in equilibrium the mean job response time in the network after adding a communication line for the sharing of jobs between nodes, for some system parameter setting, can be greater than the mean job response time in the network before adding the communication line. Indeed, two different types of paradox called weak and strong paradox have been characterized. In the range of parameter values examined, the worst case ratio of performance degradation obtained in the examined network model is about 75% and 65% for the cases of weak and strong paradox respectively.
The generic functionality of passive testing is detecting failures (fault manifestations) in a distributed system. We deal with one of the key functions of a passive tester - Trace Analysis (TA). The standard TA algor...
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ISBN:
(纸本)0889865701
The generic functionality of passive testing is detecting failures (fault manifestations) in a distributed system. We deal with one of the key functions of a passive tester - Trace Analysis (TA). The standard TA algorithms proceed by traversing a Reference Specification (RS), which is usually given in the form of a FSM automaton. The run-time performance of such algorithms is known to be poor for a large, nondeterministic RS (i.e. for real protocols). To improve this aspect of passive testing, instead of considering new TA algorithms, we try to increase the performance of existing algorithms, by changing the form of a RS to an Event Graph (EG). We define an EG and submit a detailed algorithm for its derivation. We then outline the EG-based algorithm for RS traversal. We report on the results of simulation experiments that clearly show considerable improvements in run-time performance of EG-based passive testing over previous approaches, while the functionality of failure detection is strictly retained.
We present our research findings on the practicality of using RFID for building context-aware homes in India. Our research is the result of an endeavor to bring this global trend of smart homes to India. Rather than s...
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ISBN:
(纸本)9780889866386
We present our research findings on the practicality of using RFID for building context-aware homes in India. Our research is the result of an endeavor to bring this global trend of smart homes to India. Rather than studying the effects of such an influence in its original form-building smart homes equipped with such high-end sensors as real-time, audio-video sensing, and sophisticated, environmental sensors as are popular in a typical smart home-we studied the viability of realizing ambient-intelligence using simple, low-cost, and robust RFID sensors, which we believe would be suitable to Indian dwellings in the near future. We describe the learning and prediction algorithm used in our study;we modeled time as fuzzy-sets and used Markov model for predicting the future locations of inhabitants wearing RFID bracelets. Our system provides context-aware reactive and proactive services. We modeled the uncertainties-involved in inferring users' activities from their location information-using Bayesian Belief networks or BBNs. This improved the accuracy of prediction considerably. Our experience showed that it is possible to develop cost-effective, easily deployable, context-aware homes using only RFID in India in the short-term before high-end sensing technologies mature and become commercially affordable in the longer run.
Peer-to-Peer computing has emerged in the last few years as an alternative to the traditional client/server model. The Blackboard Resource Discovery Mechanism (BRDM) facilitates the discovery of objects (files) in P2P...
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Peer-to-Peer computing has emerged in the last few years as an alternative to the traditional client/server model. The Blackboard Resource Discovery Mechanism (BRDM) facilitates the discovery of objects (files) in P2P network. We show in this paper that BRDM can also be used to find idle computers in a Peer-to-Peer network and exploits their CPU cycles to work together on solving a computational problem. We analyze the performance of BRDM in comparison with other searching algorithms. The simulations show that BRDM outperforms other algorithms discovering more idle peers than other approaches with fewer number of query messages.
For interconnection networks, designing shortest path routing algorithms is in general more difficult than designing simple routing algorithms. In this paper, we derive a shortest path routing algorithm for pyramid ne...
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For interconnection networks, designing shortest path routing algorithms is in general more difficult than designing simple routing algorithms. In this paper, we derive a shortest path routing algorithm for pyramid networks. The proposed algorithm takes O(l) time to determine a shortest path between any two nodes in a pyramid network. We also design a distributed routing algorithm such that an intermediate node takes O(1) time to confirm the next node along the shortest path without any centralized controller.
Moores law has meant that most households in the west countries own at least two perfectly functional computers. At the same time personal area networks are beginning to emerge, linking up mobile phones, PDAs,mp3/ogg,...
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ISBN:
(纸本)088986392X
Moores law has meant that most households in the west countries own at least two perfectly functional computers. At the same time personal area networks are beginning to emerge, linking up mobile phones, PDAs,mp3/ogg, Vobis players, etc. These two types of small, local, single owner/administrator networks need an appropriate model of functionality and management to provide the users with the highest degree of functionality. This paper describes an effort to create a heterogamous-networked system using Java and t JXTA project, model witch is based on clusters and grids concepts. The main function of the system is to allow central control of all peers from any peer and sharing of data resource. Another requirement is robustness and resilience to peer failure. The implementation and the test carried proved that a grid type model for home networking is a valid model.
In many distributed applications, identifying the sequence of event occurrence is useful. Doing so requires local clocks to be properly synchronized with each other. This paper presents a method of pseudo-synchronizat...
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ISBN:
(纸本)9780889867048
In many distributed applications, identifying the sequence of event occurrence is useful. Doing so requires local clocks to be properly synchronized with each other. This paper presents a method of pseudo-synchronization of clocks by making use of the occurrence time of events included in direct "happened-before" relations. The basic idea is to approximate the actual clock shift between two clocks using the minimum transmission delay of messages between a pair of hosts. Evaluation results suggest that non-base clocks are closely synchronized with a base clock without violating the direct "happened-before" relations.
The resource access and management is one of the most important key factors for grid computing. It requires a mechanism with automatically making decisions ability to support computing tasks collaborating and scheduli...
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The resource access and management is one of the most important key factors for grid computing. It requires a mechanism with automatically making decisions ability to support computing tasks collaborating and scheduling. The agent union's social activity model is one of the most suitable candidates for resource management in grid computer system. While there is no an efficient model and framework so far, this paper proposed a method for grid computing based on agent union. The method, which used agent union' s society activities as exchange and schedule foundation, has realized an efficient resource control and management framework in grid computing with media service, policy management and dynamic negotiation in agent union.
A monetary network cost issue in a parallelcomputing network with a homogeneous single-level tree topology is discussed. The monetary network cost, which is linearly dependent on the amount of divisible workload, is ...
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ISBN:
(纸本)9780889868113
A monetary network cost issue in a parallelcomputing network with a homogeneous single-level tree topology is discussed. The monetary network cost, which is linearly dependent on the amount of divisible workload, is composed of a communication cost and a computing cost. Through mathematical analysis for the monetary network cost in two different load distribution strategies (sequential distribution and simultaneous distribution), the issue of the relationship between the monetary network cost and ratio of network speed parameters is studied comprehensively. By introducing a new parameter, cost efficiency, a numerical network model suited for cost efficient parallel processing is examined. Simulation results yield insights for trends of network performance against network cost. The numerical analysis and simulation works here are worth being highlighted for high performance parallelcomputingnetworks under limited network cost.
We consider the problem of determining parallel complexity of solving banded triangular linear systems using substitution on a k-dimensional torus network. We present lower bounds on execution time for solving these s...
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ISBN:
(纸本)088986392X
We consider the problem of determining parallel complexity of solving banded triangular linear systems using substitution on a k-dimensional torus network. We present lower bounds on execution time for solving these systems, taking into account communication costs. Furthermore, optimal algorithms are designed.
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