Improved Local Search for Large Optimum Communication Spanning Tree Problems

The Optimum Communication Spanning Tree (OCST) [2] problem is NP-hard and describes the problem of finding a spanning tree that minimizes the cost defined by edge weights and communication demands, routing all communication over this tree. Given a graph G = (V,E), a distance function d : E → R+ and a requirement function r : V ×V → R+, a spanning tree T ⊆ G is wanted minimizing the cost c(T ) = ∑ i,j∈V r(i, j)c(p T i,j) where c(p T i,j) is the path length from i to j in T .