Solving the Minimum Label Spanning Tree Problem by Mathematical Programming Techniques

Figure 5

Example for a solution to (3.26)–(3.38). The octagon-shaped cycle constitutes the odd hole. The dashed arcs do not contribute to the objective function, whereas the solid arcs (which connect nodes to labels) contribute with the LP-value of the target-label as coefficient. The further arcs provide a lower bound for the contribution of all labels that need to be lifted in order to obtain a valid inequality for the initial problem.