Minimizing weighted flow time

  • Authors:
  • Nikhil Bansal;Kedar Dhamdhere

  • Affiliations:
  • IBM T.J. Watson Research, Yorktown, NY;Google Inc., Mountain View, CA

  • Venue:
  • ACM Transactions on Algorithms (TALG)
  • Year:
  • 2007

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Abstract

We consider the problem of minimizing the total weighted flow time on a single machine with preemptions. We give an online algorithm that is O(k)-competitive for k weight classes. This implies an O(log W)-competitive algorithm, where W is the maximum to minimum ratio of weights. This algorithm also implies an O(log n + log P)-approximation ratio for the problem, where P is the ratio of the maximum to minimum job size and n is the number of jobs. We also consider the nonclairvoyant setting where the size of a job is unknown upon its arrival and becomes known to the scheduler only when the job meets its service requirement. We consider the resource augmentation model, and give a (1 + ϵ)-speed, (1 +1/ϵ)-competitive online algorithm.