Non-clairvoyant Weighted Flow Time Scheduling on Different Multi-processor Models

• Published in: Approximation and Online Algorithms Vol. 7164; pp. 137 - 149
• Main Authors: Zhu, Jianqiao, Chan, Ho-Leung, Lam, Tak-Wah
• Format: Book Chapter
• Language: English
• Published: Germany Springer Berlin / Heidelberg 2012; Springer Berlin Heidelberg
• Series: Lecture Notes in Computer Science
• Subjects: Competitive Algorithm; Heterogeneous Processor; Online Algorithm; Online Scheduler; Weighted Flow Time
• ISBN: 9783642291159; 3642291155
• ISSN: 0302-9743; 1611-3349
• DOI: 10.1007/978-3-642-29116-6_12

We study non-clairvoyant scheduling to minimize weighted flow time on two different multi-processor models. In the first model, processors are all identical and jobs can possibly be speeded up by running on several processors in parallel. Under the non-clairvoyant model, the online scheduler has no information about the actual job size and degree of speed-up due to parallelism during the execution of a job, yet it has to determine dynamically when and how many processors to run the jobs. The literature contains several O(1)-competitive algorithms for this problem under the unit-weight multi-processor setting [9,10] as well as the weighted single-processor setting [2]. This paper shows the first O(1)-competitive algorithm for weighted flow time in the multi-processor setting. In the second model, we consider processors with different functionalities and only processors of the same functionality can work on the same job in parallel to achieve some degree of speed up. Here a job is modeled as a sequence of non-clairvoyant demands of different functionalities. This model is derived naturally from the classical job shop scheduling; but as far as we know, there is no previous work on scheduling to minimize flow time under this multi-processor model. In this paper we take a first step to study non-clairvoyant scheduling on this multi-processor model. Motivated by the literature on 2-machine job shop scheduling, we focus on the special case when processors are divided into two types of functionalities, and we show a non-clairvoyant algorithm that is O(1)-competitive for weighted flow time.