
 The th particle’s position of the upper level problem. 
 The th particle’s position of the lower level problem. 
 The th particle’s position of BLMPP. 
 The population size of the upper level problem. 
 The subswarm size of the lower level problem. 
 Current iteration number for the overall problem. 
 The predefined max iteration number for . 
 Current iteration number for the upper level problem. 
 Current iteration number for the lower level problem. 
 The predefined max iteration number for . 
 The predefined max iteration number for . 
 Nondomination sorting rank of the upper level problem. 
 Crowding distance value of the upper level problem. 
 Nondomination sorting rank of the lower level problem. 
 Crowding distance value of the lower level problem. 
 The th iteration population. 
 The offspring of . 
 Intermediate population. 
