Efficient sketches for the set query problem

  • Authors:
  • Eric Price

  • Affiliations:
  • MIT CSAIL

  • Venue:
  • Proceedings of the twenty-second annual ACM-SIAM symposium on Discrete Algorithms
  • Year:
  • 2011

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Abstract

We develop an algorithm for estimating the values of a vector x ε Rn over a support S of size k from a randomized sparse binary linear sketch Ax of size O(k). Given Ax and S, we can recover x' with ||x' -- xS||2 ≤ ε || x -- xS||2 with probability at least 1 − k−Ω(1). The recovery takes O(k) time. While interesting in its own right, this primitive also has a number of applications. For example, we can: 1. Improve the linear k-sparse recovery of heavy hitters in Zipfian distributions with O(k log n) space from a 1 + ε approximation to a 1 + o(1) approximation, giving the first such approximation in O(k log n) space when k ≤ O(n1-ε). 2. Recover block-sparse vectors with O(k) space and a 1 +ε approximation. Previous algorithms required either ω(k) space or ω(1) approximation.