ga_wheel.m

基因演算法genetic algorthim的程式實現

function new_popu=GA_wheel(fitness, popuReal)
%% function new_popu=GA_wheel(fitness, popuReal)
%% GA_wheel.m
%% Use of Roulette wheel selection method to get
%% new_popu.
%% For example:
%popu=10*randn(50,2);
%fitness=popu(:,1).*popu(:,2);
%new_popu=GA_wheel(fitness, popu)

%% PenChen Chou, 6-30-2001

% Remove the negative fitness values
  popu=popuReal;
  Y=min(fitness);
  if Y<0
      fitness=fitness-Y;
  end;    
  popu_n=length(fitness);
% calculate ratio of fitness
  fit_sum=sum(fitness);
  fit_mean=fit_sum/popu_n;
% Select the parent population  
  popu_select=fitness/fit_mean;
% Amplify the popu_select to make the first gene being
% selected twice
  if popu_select(1)<2
      popu_select=popu_select.^2;
  end;
  popu_select=round(popu_select);
% If no enough popu size to make the parent, make up
  Y=sum(popu_select);
  while (Y<popu_n)
      I=find(popu_select==0);
      popu_select(I(1))=popu_select(I(1))+1;
      Y=sum(popu_select); 
  end;
  %disp('===>New select population index table:');
  %popu_select'
% Get the new population
  K=1;
  for I=1:popu_n
      if popu_select(I)>0
          for J=1:popu_select(I)
            new_popu(K,:)=popu(I,:);
            K=K+1;    
            if K>popu_n, break; end; %Enough popu size
          end;
      end;
      if K>popu_n, break; end; %Enough popu size
  end;

        
  
popu=10*randn(50,2);
fitness=popu(:,1).*popu(:,2);
new_popu=GA_wheel(fitness, popu)