Solving the Minimum Label Spanning Tree Problem by Mathematical Programming Techniques

Figure 8

LP solution of DCut_t with objective value 𝑓^lp=(2+1)/6(𝑙_𝑏=1/2,𝑙_𝑐=2/3,𝑙_𝑎+𝑙_𝑑+𝑙_𝑒≥1,w.l.o.g.𝑙_𝑎=1). The green arcs depict the arc variables with their according LP values. The solution is not valid for DCut_tn, as the sum over the set of labels adjacent to node 𝑣₅ is smaller than one.