In this paper we deal with the problem of designing virtual path layouts in ATM networks when the hop-count is given and the load has to be minimized. We first prove a lower bound for networks with arbitrary topology ...
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In this paper we deal with the problem of designing virtual path layouts in ATM networks when the hop-count is given and the load has to be minimized. We first prove a lower bound for networks with arbitrary topology and arbitrary set of connection requests. This result is then applied to derive lower bounds for the following settings: (i) one-to-all (one node has to be connected to all other nodes of the network) in arbitrary networks;(ii) all-to-all (each node has to be connected to all other nodes in the network) in several classes of networks, including planar and k-separable networks and networks of bounded genus. We finally study the all-to-all setting on two-dimensional meshes and we design a virtual path layout for this problem. When the hop-count and the network degree are bounded by constants, our results show that the upper bounds proposed in this paper for the one-to-all problem in arbitrary networks and for the all-to-all problem in two-dimensional mesh networks are asymptotically optimal. Moreover, the general lower bound shows that the algorithm proposed in Gerstel (Ph.D. Thesis, Technion-Haifa, Israel, 1995) for the all-to-all problem in k-separable networks is also asymptotically optimal. The upper bound for mesh networks also shows that the lower bound presented in this paper for the all-to-all problem in planar networks is asymptotically tight. (C) 2002 Elsevier Science B.V. All rights reserved.
This paper presents a neural network approach with successful implementation for the robot task-sequencing problem. The problem addresses the sequencing of tasks comprising loading and unloading of parts into and from...
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This paper presents a neural network approach with successful implementation for the robot task-sequencing problem. The problem addresses the sequencing of tasks comprising loading and unloading of parts into and from the machines by a material-handling robot. The performance criterion is to minimize a weighted objective of the total robot travel time for a set of tasks and the tardiness of the tasks being sequenced. A three-phased parallel implementation of the neural network algorithm on Thinking Machine's CM-5 parallel computer is also presented which resulted in a dramatic increase in the speed of finding solutions. To evaluate the: performance of the neural network approach, a branch-and-bound method and a heuristic procedure have been developed for the problem. The neural network method is shown to give good results and is especially useful for solving large problems on a parallel-computing platform. (C) 2000 Elsevier Science Ltd. All rights reserved.
We present a simulation system which meets the requirements for practical application of inverse modeling in a professional environment. A tool interface for the integration of arbitrary simulation tools at the user l...
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We present a simulation system which meets the requirements for practical application of inverse modeling in a professional environment. A tool interface for the integration of arbitrary simulation tools at the user level is introduced and a methodology for the formation of simulation networks is described. A Levenberg-Marquardt optimizer automates the inverse modeling procedure. Strategics for the efficient execution of simulation tools are discussed. An example demonstrates the extraction of doping profile information on the basis of electrical measurements.
By using projections by a block of vectors in place of a single vector it is possible to parallelize the outer loop of iterative methods for solving sparse linear systems. We analyze such a scheme proposed by Coppersm...
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By using projections by a block of vectors in place of a single vector it is possible to parallelize the outer loop of iterative methods for solving sparse linear systems. We analyze such a scheme proposed by Coppersmith for Wiedemann's coordinate recurrence algorithm, which is based in part on the Krylov subspace approach. We prove that by use of certain randomizations on the input system the parallel speed up is roughly by the number of vectors in the blocks when using as many processors. Our analysis is valid for fields of entries that have sufficiently large cardinality. Our analysis also deals with an arising subproblem of solving a singular block Toeplitz system by use of the theory of Toeplitz-like matrices.
A general K -server queueing model with precedence constraints on customer services is considered. Such a system is characterized by bulk arrivals of size K , with one customer for each server, and synchronization c...
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A general K -server queueing model with precedence constraints on customer services is considered. Such a system is characterized by bulk arrivals of size K , with one customer for each server, and synchronization constraints between them and some of the previously arrived customers: Customer k (1 ≤ k ≤ K ) of the n th ( n ≥ 0) bulk arrival has to wait for the service completion of customer j (1 ≤ j ≤ K ) of the m th (0 ≤ m ≤ n ) arrival before starting its service, if there exists a precedence relation between these two customers. Such queueing systems arise naturally when modeling database concurrency control mechanisms based on “static” locking, as well as parallelcomputations where some processes may need results obtained by other processes for beginning their execution. Several performance aspects of this class of queueing systems are considered under various statistical assumptions. The stability condition, which yields the maximal system throughput, is analyzed together with the waiting and response times of individual customers, and the response times of bulks. These results are obtained from a set of recursive evolution equations which captures both the queueing and the synchronization mechanisms of the system. The stability condition is derived from a generalization of the schema of Loynes for G / G /1 queues. Integral functional equations are provided for both the transient and stationary distributions of the waiting and response times under renewal type assumptions. Various upper and lower bounds on the moments of these quantities are derived using either modifications of the precedence function or stochastic ordering techniques.
A solution to the following fundamental communication problem is presented. Suppose that n tokens are arbitrarily distributed among n processors with no processor having more than K tokens. The problem is to specify a...
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A solution to the following fundamental communication problem is presented. Suppose that n tokens are arbitrarily distributed among n processors with no processor having more than K tokens. The problem is to specify a bounded-degree network topology and an algorithm that can distribute the tokens uniformly among the processors.
The problem of efficient packet routing is central to the area of communication networks. The special case of permutation packet routing has been extensively studied in the past. While optimal algorithms for permutati...
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The problem of efficient packet routing is central to the area of communication networks. The special case of permutation packet routing has been extensively studied in the past. While optimal algorithms for permutation routing exist, they do not ‘scale up’ to give optimal solutions for the general case. Using a novel technique we obtain an optimal algorithm for the general packet routing problem. The core of our solution is an algorithm for a generalized version of the token distribution problem . This result has direct applications to the solution of the load balancing problem in distributed systems.
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