Particle Swarm Optimization Simulation

Animiation of birds movement of a swarm to get the global minimum solution

Author: Wael Mansour ([e-mail])

MSc Student, Electrical Enginering Dept, Faculty of Engineering Cairo University, Egypt

Contents

• Initialization
• Main Loop

Initialization

clear
clc
n = 50;          % Size of the swarm " no of birds "
bird_setp  = 50; % Maximum number of "birds steps"
dim = 2;          % Dimension of the problem

c2 =1.2;          % PSO parameter C1
c1 = 0.12;        % PSO parameter C2
w =0.9;           % pso momentum or inertia
fitness=0*ones(n,bird_setp);

                                       %-----------------------------%
                                       %    initialize the parameter %
                                       %-----------------------------%

R1 = rand(dim, n);
R2 = rand(dim, n);
current_fitness =0*ones(n,1);

                                 %------------------------------------------------%
                                 % Initializing swarm and velocities and position %
                                 %------------------------------------------------%

current_position = 10*(rand(dim, n)-.5);
velocity = .3*randn(dim, n) ;
local_best_position  = current_position ;


                                 %-------------------------------------------%
                                 %     Evaluate initial population           %
                                 %-------------------------------------------%

for i = 1:n
    current_fitness(i) = Live_fn(current_position(:,i));
end


local_best_fitness  = current_fitness ;
[global_best_fitness,g] = min(local_best_fitness) ;

for i=1:n
    globl_best_position(:,i) = local_best_position(:,g) ;
end
                                               %-------------------%
                                               %  VELOCITY UPDATE  %
                                               %-------------------%

velocity = w *velocity + c1*(R1.*(local_best_position-current_position)) + c2*(R2.*(globl_best_position-current_position));

                                               %------------------%
                                               %   SWARMUPDATE    %
                                               %------------------%


current_position = current_position + velocity ;

                                               %------------------------%
                                               %  evaluate anew swarm   %
                                               %------------------------%

Main Loop

iter = 0 ;        % Iterations’counter
while  ( iter < bird_setp )
iter = iter + 1;

for i = 1:n,
current_fitness(i) = Live_fn(current_position(:,i)) ;

end


for i = 1 : n
        if current_fitness(i) < local_best_fitness(i)
           local_best_fitness(i)  = current_fitness(i);
           local_best_position(:,i) = current_position(:,i)   ;
        end
 end


 [current_global_best_fitness,g] = min(local_best_fitness);


if current_global_best_fitness < global_best_fitness
   global_best_fitness = current_global_best_fitness;

    for i=1:n
        globl_best_position(:,i) = local_best_position(:,g);
    end

end


 velocity = w *velocity + c1*(R1.*(local_best_position-current_position)) + c2*(R2.*(globl_best_position-current_position));
 current_position = current_position + velocity;




x=current_position(1,:);
y=current_position(2,:);

clf
    plot(x, y , 'h')
    axis([-5 5 -5 5]);

pause(.2)


end % end of while loop its mean the end of all step that the birds move it


              [Jbest_min,I] = min(current_fitness) % minimum fitness
               current_position(:,I) % best solution






%

Jbest_min =

 -186.2872


I =

     9


ans =

   -1.5108
   -0.9673

Published with MATLAB® 7.2