TY - GEN

T1 - The competitiveness of on-line assignments

AU - Azar, Yossi

AU - Naor, Joseph

AU - Rom, Raphael

N1 - Funding Information:
*DEC Systems Research Center, 130 Lytton Ave. Palo-Alto, CA 943o1. A portion of this work was done while the author was in the department of Computer Science, Stanford University, CA 94305-2140, and supported by a Weizrnann fellowship and contract ONR NOO014-88-K-0166. t Computer Science Department, ford, CA 94305-2140. Supported K-0166. i Sun Microsystems,

PY - 1992/9/1

Y1 - 1992/9/1

N2 - Consider the on-line problem where a number of servers are ready to provide service to a set of customers. Each customer's job can be handled by any of a subset of the servers. Customers arrive one-by-one and the problem is to assign each customer to an appropriate server in a manner that will balance the load on the servers. This problem can be modeled in a natural way by a bipartite graph where the vertices of one side (customers) appear one at a time and the vertices of the other side (servers) are known in advance. We derive tight bounds on the competitive ratio in both deterministic and randomized cases. Let n denote the number of servers. In the deterministic case we provide an on-line algorithm that achieves a competitive ratio of κ = [log2 n] (up to an additive 1) and prove that this is the best competitive ratio that can be achieved by any deterministic on-line algorithm. In a similar way we prove that the competitive ratio for the randomized case is κ' = ln(n) (up to an additive 1). We conclude that for this problem, randomized algorithms differ from deterministic ones by precisely a constant factor.

AB - Consider the on-line problem where a number of servers are ready to provide service to a set of customers. Each customer's job can be handled by any of a subset of the servers. Customers arrive one-by-one and the problem is to assign each customer to an appropriate server in a manner that will balance the load on the servers. This problem can be modeled in a natural way by a bipartite graph where the vertices of one side (customers) appear one at a time and the vertices of the other side (servers) are known in advance. We derive tight bounds on the competitive ratio in both deterministic and randomized cases. Let n denote the number of servers. In the deterministic case we provide an on-line algorithm that achieves a competitive ratio of κ = [log2 n] (up to an additive 1) and prove that this is the best competitive ratio that can be achieved by any deterministic on-line algorithm. In a similar way we prove that the competitive ratio for the randomized case is κ' = ln(n) (up to an additive 1). We conclude that for this problem, randomized algorithms differ from deterministic ones by precisely a constant factor.

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AN - SCOPUS:84902101004

T3 - Proceedings of the Annual ACM-SIAM Symposium on Discrete Algorithms

SP - 203

EP - 210

BT - Proceedings of the 3rd Annual ACM-SIAM Symposium on Discrete Algorithms. SODA 1992

PB - Association for Computing Machinery

Y2 - 27 January 1992 through 29 January 1992

ER -