Improved NSGA-II algorithm with circular crowded sorting

The circular crowded sorting (CCS) is adopted to improve NSGA-Ⅱalgorithm for multi-objective optimization problem. The crowding distance of all non-dominated solutions with same rank is computed,and the solution with least crowding distance is eliminated. Then the crowding distance of remained solutions is computed,and the solution with least crowding distance is also eliminated. This operator is cycled until the appointed number non-dominated solutions have been remained. Simulations indicate the improved NSGA-Ⅱ algorithm has better performance of convergence and distribution than NSGA-Ⅱ through ZDT1~ZDT4 benchmark functions.