Hierarchical bin buffering: Online local moments for dynamic external memory arrays

  • Authors:
  • Daniel Lemire;Owen Kaser

  • Affiliations:
  • Université du Québec à Montréal, Montréal, Canada;University of New Brunswick, Saint John, Canada

  • Venue:
  • ACM Transactions on Algorithms (TALG)
  • Year:
  • 2008

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Abstract

For a massive I/O array of size n, we want to compute the first N local moments, for some constant N. Our simpler algorithms partition the array into consecutive ranges called bins, and apply not only to local-moment queries, but also to algebraic queries. With N buffers of size &sqrt;n, time complexity drops to O(&sqrt;n). A more sophisticated approach uses hierarchical buffering and has a logarithmic time complexity (O(b logb n)), when using N hierarchical buffers of size n/b. Using overlapped bin buffering, we show that only one buffer is needed, as with wavelet-based algorithms, but using much less storage.