A commander has a flow problem involving points on the battlefield. The
points are numbered 1 though m, and the distance is given for every
pair of points dij. The distances are symmetric
and unit cost is proportional to distance. |

A problem of this nature might be represented as in Fig. 26 that shows the relations between nodes as undirected edges. Since the flow model requires directed arcs, the transformation in Fig. 27, shows an equivalent model with each edge replaced by an oppositely directed pair of edges.

Figure 26. Model with nodes and edges

Figure 27. Model with directed arcs