Metrical Task Systems ( 1992 ; Borodin , Linial ,
نویسنده
چکیده
Metrical task systems (MTS), introduced by Borodin, Linial, and Saks [5], is a cost minimization problem defined on a metric space (X, dX) and informally described as follows: A given system has a set of internal states X . The aim of the system is to perform a given sequence of tasks. The performance of each task has a certain cost that depends on the task and the state of the system. The system may switch states before serving the task, and the total cost for servicing the task is the sum of the service cost of the task in the new state and the distance between the states in a metric space defined on the set of states. Following Manasse, McGeoch, and Sleator [11], an extended model is considered here, in which the set of allowable tasks may be restricted.
منابع مشابه
Unfair Problems and Randomized Algorithms for Metrical Task Systems
Borodin, Linial, and Saks introduce a general model for online systems in [Borodin et al. 1992] called metrical task systems. In this paper, the unfair two state problem, a natural generalization of the two state metrical task system problem, is studied. A randomized algorithm for this problem is presented, and it is shown that this algorithm is optimal. Using the analysis of unfair two state p...
متن کاملRandomized Algorithms for Metrical Task Systems
Borodin, Linial, and Saks introduce a general model for online systems in BLS92] called task systems and show a deterministic algorithm which achieves a competitive ratio of 2n ?1 for any metrical task system with n states. We present a randomized algorithm which achieves a competitive ratio of e=(e?1)n?1=(e?1) 1:5820n?0:5820 for this same problem. For the uniform metric space, Borodin, Linial,...
متن کاملTopology Matters: Smoothed Competitiveness of Metrical Task Systems
We consider metrical task systems, a general framework to model online problems. Borodin, Linial and Saks [BLS92] presented a deterministic work function algorithm (WFA) for metrical task systems having a tight competitive ratio of 2n−1. We present a smoothed competitive analysis of WFA. Given an adversarial task sequence, we smoothen the request costs by means of a symmetric additive smoothing...
متن کاملThe influence of lookahead in competitive on-line algorithms
In the competitive analysis of on-line problems, an on-line algorithm is presented with a sequence of requests to be served. The on-line algorithm must satisfy each request without the knowledge of any future requests. We consider the question of lookahead in on-line problems: What improvement can be achieved in terms of competitiveness, if the on-line algorithm sees not only the present reques...
متن کاملOn Multi-threaded Metrical Task Systems
Traditionally, on-line problems have been studied under the assumption that there is a unique sequence of requests that must be served. This approach is common to most general models of on-line computation, such as Metrical Task Systems. However, there exist on-line problems in which the requests are organized in more than one independent thread. In this more general framework, at every moment ...
متن کامل