Speed is as powerful as clairvoyance

  • Authors:
  • Bala Kalyanasundaram;Kirk Pruhs

  • Affiliations:
  • Univ. of Pittsburgh, Pittsburgh, PA;Univ. of Pittsburgh, Pittsburgh, PA

  • Venue:
  • Journal of the ACM (JACM)
  • Year:
  • 2000

Quantified Score

Hi-index 0.01

Visualization

Abstract

We introduce resource augmentation as a method for analyzing online scheduling problems. In resource augmentation analysis the on-line scheduler is given more resources, say faster processors or more processors, than the adversary. We apply this analysis to two well-known on-line scheduling problems, the classic uniprocessor CPU scheduling problem 1 |ri, pmtn|&Sgr; Fi, and the best-effort firm real-time scheduling problem 1|ri, pmtn| &Sgr; wi( 1- Ui). It is known that there are no constant competitive nonclairvoyant on-line algorithms for these problems. We show that there are simple on-line scheduling algorithms for these problems that are constant competitive if the online scheduler is equipped with a slightly faster processor than the adversary. Thus, a moderate increase in processor speed effectively gives the on-line scheduler the power of clairvoyance. Furthermore, the on-line scheduler can be constant competitive on all inputs that are not closely correlated with processor speed. We also show that the performance of an on-line scheduler is best-effort real time scheduling can be significantly improved if the system is designed in such a way that the laxity of every job is proportional to its length.