An Improved Discrete PSO for Tugboat Assignment Problem under a Hybrid Scheduling Rule in Container Terminal

Pseudocode 2

Step  1. (Initializing)

Initialize the parameters: the max iteration , the no-improvement iteration , swarm size ,

each particle’s location and velocity, the local best location and the global best location .

Step  2. (Updating and Fitness Calculation)

Set the iteration number t = 1

Repeat

 For each particle, generate random parameter: , , , , ,

 Update the velocity of each particle according to (22)

 Update the position of each particle according to (23)

 Check the new position is a feasible assignment according to (8)

 If ( is not a feasible assignment) then

  Mutation to a feasible assignment

 End if

 Generate the scheduling sequence

 Calculate the turnaround time as fitness of

 Update ,

 Check the improvement of

 If is improved then

  _flag = 0

 Else

  _flag = _flag + 1

 End if

  = + 1

 Untill > or c_flag =

Step  3. (Final stage)

Output the best tugboat assignment, the ship scheduling sequence, the start docking time and the

completion docking time of eachship, the turnaround time of the best assignment.