细菌觅食算法---源码

%% Bacterial foraging
% Animiation of bacteria movement to get the global minimum solution every chemotactic
%
% Author: Wael Mansour (wael192@yahoo.com)
%
% MSc Student, Electrical Enginering Dept,
% Faculty of Engineering Cairo University, Egypt


%%
%Initialization
clear all  
clc
p=2;                         % dimension of search space
s=26;                        % The number of bacteria
Nc=50;                       % Number of chemotactic steps
Ns=4;                        % Limits the length of a swim
Nre=4;                       % The number of reproduction steps
Ned=2;                       % The number of elimination-dispersal events
Sr=s/2;                      % The number of bacteria reproductions (splits) per generation
Ped=0.25;                    % The probabilty that each bacteria will be eliminated/dispersed
c(:,1)=0.05*ones(s,1);       % the run length 
for m=1:s                    % the initital posistions
    P(1,:,1,1,1)= 50*rand(s,1)';
    P(2,:,1,1,1)= .2*rand(s,1)';
   %P(3,:,1,1,1)= .2*rand(s,1)';
end                                                                 
    
%%
%Main loop
   

%Elimination and dispersal loop
for ell=1:Ned
   

%Reprodution loop


    for K=1:Nre   

%  swim/tumble(chemotaxis)loop  

        for j=1:Nc
           
            for i=1:s       
                J(i,j,K,ell)=Live_fn(P(:,i,j,K,ell));        

% Tumble

                       
                Jlast=J(i,j,K,ell);  
                Delta(:,i)=(2*round(rand(p,1))-1).*rand(p,1);                     
                P(:,i,j+1,K,ell)=P(:,i,j,K,ell)+c(i,K)*Delta(:,i)/sqrt(Delta(:,i)'*Delta(:,i)); % This adds a unit vector in the random direction           
 
% Swim (for bacteria that seem to be headed in the right direction)    
               
                J(i,j+1,K,ell)=Live_fn(P(:,i,j+1,K,ell)); 
                m=0;         % Initialize counter for swim length
                    while m<Ns    
                          m=m+1;
                          if J(i,j+1,K,ell)<Jlast 
                             Jlast=J(i,j+1,K,ell);   
                            P(:,i,j+1,K,ell)=P(:,i,j+1,K,ell)+c(i,K)*Delta(:,i)/sqrt(Delta(:,i)'*Delta(:,i)) ; 
                             J(i,j+1,K,ell)=Live_fn(P(:,i,j+1,K,ell)); 
                          else      
                             m=Ns ;    
                          end       
                   
                    end
                J(i,j,K,ell)=Jlast;
                sprintf('The value of interation i %3.0f ,j = %3.0f  , K= %3.0f, ell= %3.0f' , i, j, K ,ell );
                  
            end % Go to next bacterium
           
            x = P(1,:,j,K,ell);
            y = P(2,:,j,K,ell);
            clf   
            plot(x, y , 'h')  
            axis([-5 5 -5 5]);
            pause(.1)
        end  % Go to the next chemotactic   

                
%Reprodution                                             
        Jhealth=sum(J(:,:,K,ell),2);              % Set the health of each of the S bacteria
        [Jhealth,sortind]=sort(Jhealth);          % Sorts the nutrient concentration in order of ascending
        P(:,:,1,K+1,ell)=P(:,sortind,Nc+1,K,ell);
        c(:,K+1)=c(sortind,K);                    % And keeps the chemotaxis parameters with each bacterium at the next generation
                                    

%Split the bacteria (reproduction)                            
            for i=1:Sr
                P(:,i+Sr,1,K+1,ell)=P(:,i,1,K+1,ell); % The least fit do not reproduce, the most fit ones split into two identical copies 
                c(i+Sr,K+1)=c(i,K+1);                
            end  
        end %  Go to next reproduction   


%Eliminatoin and dispersal
        for m=1:s
            if  Ped>rand % % Generate random number
                P(1,:,1,1,1)= 50*rand(s,1)';
                P(2,:,1,1,1)= .2*rand(s,1)';
               %P(3,:,1,1,1)= .2*rand(s,1)';  
            else
                P(:,m,1,1,ell+1)=P(:,m,1,Nre+1,ell); % Bacteria that are not dispersed
            end       
        end
    end % Go to next elimination and disperstal

%Report
           reproduction = J(:,1:Nc,Nre,Ned);
           [jlastreproduction,O] = min(reproduction,[],2);  % min cost function for each bacterial
           [Y,I] = min(jlastreproduction)
           pbest=P(:,I,O(I,:),K,ell)
     
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  

function fposition=Live_fn(x)

    p=0;q=0;
    for k=1:5
    p=p+k*cos((k+1)*x(1)+k);
    q=q+k*cos((k+1)*x(2)+k);
    end

fposition=p*q+(x(1)+1.42513)^2+(x(2)+.80032)^2;
%%%%%%%%%%%%%%%%%%%%%%% over%%%%%%%%%%%%%%%