An O(n3log n) deterministic and an O(n3) Las Vegs isomorphism test for trivalent graphs

  • Authors:
  • Zvi Galil;Christoph M. Hoffmann;Eugene M. Luks;Claus P. Schnorr;Andreas Weber

  • Affiliations:
  • Columbia Univ., New York, NY and Tel-Aviv Univ., Tel-Aviv, Israel;Purdue Univ., West Lafayette, IN;Univ. of Oregon, Eugene;Univ. of Frankfurt, Frankfurt, W. Germany;Univ. of Frankfurt, Frankfurt, W. Germany

  • Venue:
  • Journal of the ACM (JACM)
  • Year:
  • 1987

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Abstract

This paper describes an O(n3logn) deterministic algorithm and an O(n3) Las Vegas algorithm for testing whether two given trivalent graphs on n vertices are isomorphic. In fact, the algorithms construct the set of all isomorphisms between two such graphs, presenting, in particular, generators for the group of all automorphisms of a trivalent graph. The algorithms are based upon the original polynomial-time solution to these problems by Luks but they introduce numerous speedups. These include improved permutation-group algorithms that exploit the structure of the underlying 2-groups. A remarkable property of the Las Vegas algorithm is that it computes the set of all isomorphisms between two trivalent graphs for the cost of computing only those isomorphisms that map a specified edge to a specified edge.