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A 2‐path approach for odd‐diameter‐constrained minimum spanning and Steiner trees
Author(s) -
Gouveia Luis,
Magnanti Thomas L.,
Requejo Cristina
Publication year - 2004
Publication title -
networks
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.977
H-Index - 64
eISSN - 1097-0037
pISSN - 0028-3045
DOI - 10.1002/net.20034
Subject(s) - polyhedron , spanning tree , integer programming , steiner tree problem , mathematics , combinatorics , minimum spanning tree , euclidean minimum spanning tree , intersection (aeronautics) , path (computing) , linear programming relaxation , tree (set theory) , node (physics) , shortest path problem , cutting plane method , relaxation (psychology) , linear programming , euclidean geometry , graph , mathematical optimization , computer science , minimum degree spanning tree , psychology , social psychology , geometry , structural engineering , engineering , programming language , aerospace engineering
In a previous article, using underlying graph theoretical properties, Gouveia and Magnanti (2003) described several network flow‐based formulations for diameter‐constrained tree problems. Their computational results showed that, even with several enhancements, models for situations when the tree diameter D is odd proved to be more difficult to solve than those when D is even. In this article we provide an alternative modeling approach for the situation when D is odd. The approach views the diameter‐constrained minimum spanning tree as being composed of a variant of a directed spanning tree (from an artificial root node) together with two constrained paths, a shortest and a longest path, from the root node to any node in the tree. We also show how to view the feasible set of the linear programming relaxation of the new formulation as the intersection of two integer polyhedra, a so‐called triangle‐tree polyhedron and a constrained path polyhedron. This characterization improves upon a model of Gouveia and Magnanti (2003) whose linear programming relaxation feasible set is the intersection of three rather than two integer polyhedra. The linear programming gaps for the tightened model are very small, typically less than 0.5%, and are usually one third to one tenth of the gaps of the best previous model described in Gouveia and Magnanti (2003). Moreover, using the new model, we have been able to solve large Euclidean problem instances that are not solvable by the previous approaches. © 2004 Wiley Periodicals, Inc.