A Study on Efficient Online Scheduling Algorithms

• Main Authors: Tsung-Chien Wu, 吳宗謙
• Other Authors: Dr. Jen-Chun Chang
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/36744735116164154974

碩士 === 國立臺北大學 === 資訊工程學系 === 103 === We study the bounded-delay model for Qualify-of-Service buffer management. Time is discrete. There is a buffer. Unit-length jobs (also called packets) arrive at the buffer over time. Each packet has an integer release time, an integer deadline, and a positive real value. A packet’s characteristics are not known to an online algorithm until the packet actually arrives. So it is a classic online algorithm problem. In each time step, at most one packet can be sent out of the buffer. If the packet cannot be sent until its deadline, the packet would be abandon from buffer. So algorithm’s object is to maximize the total value of the packets sent by their respective deadlines in an online manner. An online algorithm’s performance is usually measured in terms of competitive ratio, when this online algorithm is compared with an optimal algorithm achieving the maximum total value. If an online algorithm’s total value is no less than 1/c what an optimal algorithm sent, we can call this algorithm is c-competitive. In this paper, we propose a new online algorithm call VRα by improving modified greedy algorithm. We give a proof that VRα obtains 2- competitive for any 1 ≤ α ≤ 2.