Testing graph isomorphism

  • Authors:
  • Eldar Fischer;Arie Matsliah

  • Affiliations:
  • Israel institute of technology, Technion City, Haifa, Israel;Israel institute of technology, Technion City, Haifa, Israel

  • Venue:
  • SODA '06 Proceedings of the seventeenth annual ACM-SIAM symposium on Discrete algorithm
  • Year:
  • 2006

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Abstract

We deal with the question of how many queries are required to distinguish between the case that two graphs G and H on n vertices are isomorphic, and the case that they are ε-far, that is they differ in more than ε(n2) pairs for all possible bijections of their vertices. Querying is defined as probing the adjacency matrix of any one of the two graphs, i.e. asking if a pair of vertices forms an edge of the graph or not.We investigate both one-sided error and two-sided error testers under two possible settings: The first setting is where both graphs need to be queried; and the second setting is where one of the graphs is known to the algorithm in advance.We prove that the query complexity of the one-sided error testing problem is Θ(n3/2) if both graphs need to be queried, and that it is Θ(n) if one of the graphs is known in advance (where the Θ notation hides polylogarithmic factors in the upper bounds). For the two-sided error testers we prove that the query complexity is Θ(√n when one of the graphs is known in advance, and we show that the query complexity lies between Ω(n) and Õ(n5/4) if both G and H need to be queried. All of our algorithms are additionally non-adaptive, while all of our lower bounds apply for adaptive testers as well as non-adaptive ones.