Figure 2.

TSP maps used in the experiments. (a–e) ‘Unrestricted’ instances of four-, five-, six-, seven- and eight-city TSP (left panels). We designed each map such that its inter-city distances produce a unimodal-like distribution of lengths of possible tours with a mean value of approximately 150 (right panels) and gives a unique shortest (blue) and longest tour of lengths 100 and 200, respectively. This is a natural approach for an unbiased evaluation of the dependence of the search ability on n.