Searching in random partially ordered sets

  • Authors:
  • R. Carmo;J. Donadelli;Y. Kohayakawa;E. Laber

  • Affiliations:
  • Departamento de Informática, Universidade Federal do Paraná, Centro Politécnico da UFPR, Curitiba and Instituto de Matemática e Estatística, Universidade de São Paulo ...;Departamento de Informática, Universidade Federal do Paraná, Centro Politécnico da UFPR, Curitiba, PR 81531-990, Brazil;Instituto de Matemática e Estatística, Universidade de São Paulo, Rua do Matdão 1010, São Paulo SP 05508-090, Brazil;Departamento de Informática Pontificia Univ. Católica do Rio de Janeiro, R. Marquês de São Vicente 225, Rio de Janeiro RJ, Brazil

  • Venue:
  • Theoretical Computer Science - Latin American theorotical informatics
  • Year:
  • 2004

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Abstract

We consider the problem of searching for a given element in a partially ordered set. More precisely, we address the problem of computing efficiently near-optimal search strategies for typical partial orders under two classical models for random partial orders, the random graph model and the uniform model.We shall show that the problem of determining an optimal strategy is NP-hard, but there are simple, fast algorithms able to produce near-optimal search strategies for typical partial orders under the two models of random partial orders that we consider. We present a (1 + o(1))- approximation algorithm for typical partial orders under the random graph model (constant p) and present a 6.34-approximation algorithm for typical partial orders under the uniform model. Both algorithms run in polynomial time.