  Recently different evolutionary computation approaches have been developed
that generate sets of high quality diverse solutions for a given optimisation
problem. Many studies have considered diversity 1) as a mean to explore niches
in behavioural space (quality diversity) or 2) to increase the structural
differences of solutions (evolutionary diversity optimisation). In this study,
we introduce a co-evolutionary algorithm to simultaneously explore the two
spaces for the multi-component traveling thief problem. The results show the
capability of the co-evolutionary algorithm to achieve significantly higher
diversity compared to the baseline evolutionary diversity algorithms from the
the literature.
