The capacitated K-center problem is a basic facility location problem, where we are asked to locate K facilities in a graph and to assign vertices to facilities, so as to minimize the maximum distance from a vertex to the facility to which it is assigned. Moreover, each facility may be assigned at most L vertices. This problem is known to be NP-hard. We give polynomial time approximation algorithms for two different versions of this problem that achieve approximation factors of 5 and 6. We also study some generalizations of this problem.

/pdf/the-capacitated-k-center-problem-1h2iz1qo3a.pdf

The Capacitated K -Center Problem

How to Allocate Network Centers

The importance of file migration is increasing because of its potential to improve the performance of distributed office, manufacturing and hospital information systems. To encourage research in the file migration problem, the authors summarize accomplishments of researchers of the problem, provide a detailed comparison of file migration and dynamic file allocation problems, and identify important areas of research to support the development of effective file migration policies.

/pdf/dynamic-file-migration-in-distributed-computer-systems-1e59nrlaij.pdf

Dynamic file migration in distributed computer systems

This paper investigates the optimal placement of proxies of a Web server on the Internet, with the consideration of both read and update operations to the data on the Web server. We first study the problem of optimal placement of k proxies in a system to minimize the total access cost to the Web server. Then, for an unknown number of proxies, we find the optimal number of proxies required in the system. The problems are formulated by using the dynamic programming method and the optimal solutions are obtained. Simulations have been conducted to evaluate the performance of the proposed algorithms and to demonstrate how the effectiveness of proxy placement is affected by various factors, such as network traffic load, number of proxies, read‐write ratio and proxy hit ratio.

http://www.cs.cityu.edu.hk/~jia/research/compJour2.pdf

Placement of Web-server proxies with consideration of read and update operations on the Internet

Achieving optimal data storage position in wireless sensor networks

In this paper, we are going to examine the problem of optimal file allocation In arbitrary computer networks This problem has been shown to be NP-complete [CHAHD76, ESWAR74] Several authors TCHU69, CASEY72, CHAND76, MAHMD76] have stud3ed this problem using analytical, heurlstlc and lmearInteger programmlng methods But these techniques only tend to demonstrate their relative efficiencies in fIndIng solutions to known problems and for small values of the number of nodes In the network They did not provide any mathematical analysis of the worst case sltuatlon of their techniques Hence, they falled to establish bounds on the devlatlon of their solutions In terms of exact solutions for problems with no known optimal solutlons They also did not establish the time and space complexltles of their algorithms This has motivated us to develop a polynomial appro,;'at:on algorithm which guarantees a reallstlc worst case bound

M. S. Krishnamoorthy

Papers

An approximation algorithm to the file allocation problem in computer networks