Optimal Time-Space Trade-Offs for Sorting

  • Authors:
  • Jakob Pagter;Theis Rauhe

  • Affiliations:
  • -;-

  • Venue:
  • FOCS '98 Proceedings of the 39th Annual Symposium on Foundations of Computer Science
  • Year:
  • 1998

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Abstract

We study the fundamental problem of sorting in a sequential model of computation and in particular consider the time-space trade-off (product of time and space) for this problem.Beame has shown a lower bound of $\Omega(n^2)$ for this product leaving a gap of a logarithmic factor up to the previously best known upper bound of $O(n^2\log n)$ due to Frederickson. Since then, no progress has been made towards tightening this gap.The main contribution of this paper is a comparison based sorting algorithm which closes the gap by meeting the lower bound of Beame. The time-space product $O(n^2)$ upper bound holds for the full range of space bounds between $\log n$ and $n/\log n$. Hence in this range our algorithm is optimal for comparison based models as well as for the very powerful general models considered by Beame.