On the Hardness of Constructing Minimal Biconnected Spanning Subgraphs in Complete Graphs with Sharpened Triangle Inequality (Articolo in rivista)

Type
Label
  • On the Hardness of Constructing Minimal Biconnected Spanning Subgraphs in Complete Graphs with Sharpened Triangle Inequality (Articolo in rivista) (literal)
Anno
  • 2002-01-01T00:00:00+01:00 (literal)
Alternative label
  • Bockenhauer, H.J.; Bongartz, D.; Hromkovic, J.; Klasing, R.; Proietti, G.; Seiber, S.; Unger, W. (2002)
    On the Hardness of Constructing Minimal Biconnected Spanning Subgraphs in Complete Graphs with Sharpened Triangle Inequality
    in Lecture notes in computer science
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Bockenhauer, H.J.; Bongartz, D.; Hromkovic, J.; Klasing, R.; Proietti, G.; Seiber, S.; Unger, W. (literal)
Pagina inizio
  • 59 (literal)
Pagina fine
  • 70 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
  • 2556 (literal)
Rivista
Note
  • ISI Web of Science (WOS) (literal)
Titolo
  • On the Hardness of Constructing Minimal Biconnected Spanning Subgraphs in Complete Graphs with Sharpened Triangle Inequality (literal)
Abstract
  • In this paper we investigate the problem of finding a 2-connected spanning subgraph of minimal cost in a complete and weighted graph $G$. This problem is known to be APX-hard, both for the edge- and for the vertex-connectivity case. Here we prove that the APX-hardness still holds even if one restricts the edge costs to an interval $[1, 1+\epsilon]$, for an arbitrary small $\epsilon > 0$. This result implies the first explicit lower bound on the approximability of the general problems. On the other hand, if the input graph satisfies the sharpened $\beta$-triangle inequality, then a $\left(\frac{2}+\frac{1} \cdot \frac{\beta}{1-\beta}\right)$-approximation algorithm is designed. This ratio tends to $ with $\beta$ tending to $\frac{1}{2}$, and it improves the previous known bound of $\frac{2}$, holding for graphs satisfying the triangle inequality, as soon as $\beta < \frac{5}{7}$. Furthermore, a generalized problem of increasing to 2 the edge-connectivity of any spanning subgraph of $G$ by means of a set of edges of minimum cost is considered. This problem is known to admit a 2-approximation algorithm. Here we show that whenever the input graph satisfies the sharpened $\beta$-triangle inequality with $\beta < \frac{2}$, then this ratio can be improved to $\frac{\beta}{1-\beta}$. (literal)
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