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Online Algorithms Susanne Albers

Summary: Online Algorithms
Susanne Albers
University of Freiburg, Germany
1 Introduction
This book chapter reviews fundamental concepts and results in the area of
online algorithms. We first address classical online problems and then study
various applications of current interest.
Online algorithms represent a theoretical framework for studying prob-
lems in interactive computing. They model, in particular, that the input in
an interactive system does not arrive as a batch but as a sequence of input
portions and that the system must react in response to each incoming por-
tion. Moreover, they take into account that at any point in time future input
is unknown. As the name suggests, online algorithms consider the algorith-
mic aspects of interactive systems: We wish to design strategies that always
compute good output and keep a given system in good state. No assumptions
are made about the input stream. The input can even be generated by an
adversary that creates new input portions based on the system's reactions to
previous ones. We seek algorithms that have a provably good performance.
Formally, an online algorithm receives a sequence of requests
= (1), . . . , (m). These requests must be served in the order of occur-


Source: Albers, Susanne - Institut für Informatik, Humboldt-Universität zu Berlin


Collections: Computer Technologies and Information Sciences