Improved imperialist competitive algorithm for flexible flow shop scheduling

In this paper, we investigate the flexible flow-shop scheduling problem (FFSP). The mathematical model is established to minimize the makespan. Improved Imperialist Competitive Algorithm (IICA) is proposed as the global searching mechanism for this optimization problem. Based on the standard imperialist competitive algorithm, two improvements, reform operation and elite individual retention strategy have been introduced. At the same time, to improve the diversity of solutions, the Hamming distance has also been introduced to select the individuals. Through the standard instance tests, the proposed IICA outperforms the genetic algorithm and the standard imperialist competitive algorithm in terms of the convergence speed and global optimum searching for the flexible flow-shop scheduling problem¹.