Randomized on-line scheduling on two uniform machines

✍ Scribed by Leah Epstein; John Noga; Steve Seiden; Jiří Sgall; Gerhard Woeginger

• Publisher: Springer US
• Year: 2001
• Tongue: English
• Weight: 178 KB
• Volume: 4
• Category: Article
• ISSN: 1094-6136
• DOI: 10.1002/jos.60

✦ Synopsis

We study the problem of on-line scheduling on two uniform machines with speeds 1 and s*1. A +1.61803 competitive deterministic algorithm was already known. We present the "rst randomized results for this problem: We show that randomization does not help for speeds s*2, but does help for all s(2. We present a simple memoryless randomized algorithm with competitive ratio (4!s)(1#s)/4)1.56250. We analyse other randomized algorithms that demonstrate that the randomized competitive ratio is at most 1.52778 for any s. These algorithms are barely random, i.e. they use only a constant number of random bits. Finally, we present a 1#s/(s#s#1) competitive deterministic algorithm for the preemptive version of this problem. For any s, it is best possible even among randomized preemptive algorithms.