Suppose that DC power is generated at a central plant at a certain voltage, and we are required to serve a multiplicity of destination loads with a power distribution network of copper wires. The constraints are Ohm's law, Kirchoff's voltage and current laws, and that every load is guaranteed a minimum specified voltage. We want to design the distribution network, subject to the constraints, to
minimize the total volume of copper. This optimization problem is non-convex.  If there are no topological constraints the globally optimal network comprises pairs of wires which independently connect
the generator to each load.  This noncooperative scheme - the optimality of which is provable by inspection - is embodied in Thomas Edison's remarkable 1879 "feeder and main" invention which was an essential innovation for his electric lighting system.