 
Summary: New OnLine Algorithms for the Page Replication Problem
Susanne Albersy Hisashi Kogaz
Abstract
We present improved competitive online algorithms for the page replication problem and
concentrate on important network topologies for which algorithms with a constant compet
itive ratio can be given. We develop an optimal randomized online replication algorithm
for trees and uniform networks; its competitive ratio is approximately 1.58. This perfor
mance holds against oblivious adversaries. We also give a randomized memoryless replica
tion algorithm for trees and uniform networks that is 2competitive against adaptive online
adversaries. Furthermore we consider online replication algorithms for rings and present
general techniques that transform ccompetitive algorithms for trees into 2ccompetitive al
gorithms for rings. As a result we obtain a randomized online algorithm for rings that is
3.16competitive. We also derive two 4competitive online algorithms for rings which are
either deterministic or randomized and memoryless. Again, the randomized results hold
against oblivious adversaries. Apart from these techniques, we nally give a randomized
memoryless replication algorithm for rings that is 4competitive against adaptive online
adversaries.
1 Introduction
This paper deals with problems that arise in the memory management of large multiprocessor
systems. Such multiprocessing environments typically consist of a network of processors, each
