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