Streaming algorithms for some problems in log-space

  • Authors:
  • Ajesh Babu;Nutan Limaye;Girish Varma

  • Affiliations:
  • Tata Institute of Fundamental Research, Mumbai, India;Tata Institute of Fundamental Research, Mumbai, India;Tata Institute of Fundamental Research, Mumbai, India

  • Venue:
  • TAMC'10 Proceedings of the 7th annual conference on Theory and Applications of Models of Computation
  • Year:
  • 2010

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Abstract

In this paper, we give streaming algorithms for some problems which are known to be in deterministic log-space, when the number of passes made on the input is unbounded If the input data is massive, the conventional deterministic log-space algorithms may not run efficiently We study the complexity of the problems when the number of passes is bounded. The first problem we consider is the membership testing problem for deterministic linear languages, DLIN Extending the recent work of Magniez et al.[11](to appear in STOC 2010), we study the use of fingerprinting technique for this problem We give the following streaming algorithms for the membership testing of DLIN s: a randomized one pass algorithm that uses O(logn) space (one-sided error, inverse polynomial error probability), and also a p-pass O(n/p)-space deterministic algorithm We also prove that there exists a language in DLIN, for which any p-pass deterministic algorithm for membership testing, requires Ω(n/p) space We also study the application of fingerprinting technique to visibly pushdown languages, VPL s. The other problem we consider is, given a degree sequence and a graph, checking whether the graph has the given degree sequence, Deg-Seq We prove that, any p-pass deterministic algorithm that takes as its input a degree sequence, followed by an adjacency list of a graph, requires Ω(n/p) space to decide Deg-Seq However, using randomness, for a more general input format: degree sequence, followed by a list of edges in any arbitrary order, Deg-Seq can be decided in O(logn) space We also give a p-pass, O(n/p)-space deterministic algorithm for Deg-Seq.