Research Article

A Decomposition-Based Unified Evolutionary Algorithm for Many-Objective Problems Using Particle Swarm Optimization

Algorithm 3

Main algorithm.
Input: Number of particles in , the maximum generation is ,
 number if inner iterations .
Output: The approximate in global repository
 (1) Decompose the objectives according to Algorithm 1.
 (2) Randomly initialize the position of each particle;
   initialize the velocity , .
 (3) Store the nondominated particles into the subgroup repository ;
   Update .
 (4) Initialize the unification factor ; calculate entropies for each subgroup.
 (5) Initialize each particle’s best position .
 (6) while do
 (7)  for = 1 :  do
 (8)   (a) Update the velocity and position according to the unified particle
       swarm optimization, the selection procedures of and
       follow the algorithm in Section 5.2.
 (9)   (b) If the particles’ position beyond the decision space, the corresponding
       variable should be replaced by the value of the boundaries.
 (10)   (c) Evaluate the new cost of each particle in .
 (11)   (d) Update , add new nondominated particles in and move
       the dominated solutions out. If the number of particles exceed
       the capacity of , filter the according to dominance rank.
 (12)   (e) Update . If the number of particles exceed
       the capacity of , filter the with crowding reference.
 (13)   (f) Calculate , according to Equation (6) and Equation (7).
 (14)   (g) .
 (15)  end for
 (16)  Regroup the objectives according to Algorithm 1.
 (17)  Recompose the subgroup repositories.
 (18) end while