The graph construction algorithms often need to make a random choice among several alternative locations for the current department. This random choice is made based on pseudo random numbers, generated from an initial seed. An algorithm will always make the same random choices if it is given the same random seed, and hence will create the same adjacency graph. The seed has to be a positive number in the range of [1,32767]. If a seed of zero is given, then the computer will pick a random seed based on the computer clock.