GreedyMAX-type algorithms for the maximum independent set problem

  • Authors:
  • Piotr Borowiecki;Frank Göring

  • Affiliations:
  • Department of Algorithms and System Modeling, Faculty of Electronics, Telecommunications and Informatics, Gdańsk University of Technology, Gdańsk, Poland;Fakultät für Mathematik, TU Chemnitz, Chemnitz, Germany

  • Venue:
  • SOFSEM'11 Proceedings of the 37th international conference on Current trends in theory and practice of computer science
  • Year:
  • 2011

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Abstract

A maximum independent set problem for a simple graph G = (V, E) is to find the largest subset of pairwise nonadjacent vertices. The problem is known to be NP-hard and it is also hard to approximate. Within this article we introduce a non-negative integer valued function p defined on the vertex set V (G) and called a potential function of a graph G, while P(G) = maxv∈V(G) p(v) is called a potential of G. For any graph P(G) ≤ Δ(G), where Δ(G) is the maximum degree of G. Moreover, Δ(G) - P(G) may be arbitrarily large. A potential of a vertex lets us get a closer insight into the properties of its neighborhood which leads to the definition of the family of GreedyMAX-type algorithms having the classical GreedyMAX algorithm as their origin. We establish a lower bound 1/(P + 1) for the performance ratio of GreedyMAX-type algorithms which favorably compares with the bound 1/(Δ + 1) known to hold for GreedyMAX. The cardinality of an independent set generated by any GreedyMAX-type algorithm is at least Σv∈V(G)(p(v)+1)-1, which strengthens the bounds of Turáan and Caro-Wei stated in terms of vertex degrees.