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Online Choice of Online Algorithms Yossi Azar \Lambda Andrei Z. Broder \Lambda Mark S. Manasse \Lambda

Summary: Chapter 1
On­line Choice of On­line Algorithms
Yossi Azar \Lambda Andrei Z. Broder \Lambda Mark S. Manasse \Lambda
Let fA1 ; A2 ; : : : ; Amg be a set of on­line algorithms for
a problem P with input set I. We assume that P can
be represented as a metrical task system. Each A i has
a competitive ratio a i with respect to the optimum off­
line algorithm, but only for a subset of the possible inputs
such that the union of these subsets covers I. Given this
setup, we construct a generic deterministic on­line algorithm
and a generic randomized on­line algorithm for P that are
competitive over all possible inputs. We show that their
competitive ratios are optimal up to constant factors. Our
analysis proceeds via an amusing card game.
1 Introduction
A common trick of the trade in algorithm design is to
combine several algorithms using round robin execution.
The basic idea is that, given a set of m algorithms
for a problem P , one can simulate them one at a


Source: Azar, Yossi - School of Computer Science, Tel Aviv University


Collections: Computer Technologies and Information Sciences