www.pudn.com > geneticbs2rv.rar > MUTBGA.M

% MUTBGA.M       (real-value MUTation like Breeder Genetic Algorithm) 
% 
% This function takes a matrix OldChrom containing the real 
% representation of the individuals in the current population, 
% mutates the individuals with probability MutR and returns 
% the resulting population. 
% 
% This function implements the mutation operator of the Breeder Genetic 
% Algorithm. (Muehlenbein et. al.) 
% 
% Syntax:  NewChrom = mutbga(OldChrom, FieldDR, MutOpt) 
% 
% Input parameter: 
%    OldChrom  - Matrix containing the chromosomes of the old 
%                population. Each line corresponds to one individual. 
%    FieldDR   - Matrix describing the boundaries of each variable. 
%    MutOpt    - (optional) Vector containing mutation rate and shrink value 
%                MutOpt(1): MutR - number containing the mutation rate - 
%                           probability for mutation of a variable 
%                           if omitted or NaN, MutR = 1/variables per individual 
%                           is assumed 
%                MutOpt(2): MutShrink - (optional) number for shrinking the 
%                           mutation range in the range [0 1], possibility to 
%                           shrink the range of the mutation depending on, 
%                           for instance actual generation. 
%                           if omitted or NaN, MutShrink = 1 is assumed 
% 
% Output parameter: 
%    NewChrom  - Matrix containing the chromosomes of the population 
%                after mutation in the same format as OldChrom. 
 
% Author:     Hartmut Pohlheim 
% History:    23.11.93     file created 
%             24.11.93     function optimised (for,for-loop to for-loop) 
%                          mutation rate included 
%                          style improved 
%             06.12.93     change of function name 
%                          check of boundaries after mutation out of loop 
%             16.12.93     NewMutMat and OldMutMat included for compability 
%             16.02.94     preparation for multi-subpopulations at once 
%             25.02.94     NewMutMat and OldMutMat removed (now in mutran10.m) 
%                          clean up 
%                          change of function name in mutbga.m 
%             03.03.94     Lower and Upper directly used (less memory) 
%             19.03.94     multipopulation support removed 
%                          more parameter checks 
%             27.03.94     Delta exact calculated, for loop saved 
 
 
function NewChrom = mutbga(OldChrom, FieldDR, MutOpt); 
 
% Check parameter consistency 
   if nargin < 2,  error('Not enough input parameter'); end 
 
   % Identify the population size (Nind) and the number of variables (Nvar) 
   [Nind,Nvar] = size(OldChrom); 
 
   [mF, nF] = size(FieldDR); 
   if mF ~= 2, error('FieldDR must be a matrix with 2 rows'); end 
   if Nvar ~= nF, error('FieldDR and OldChrom disagree'); end 
 
   if nargin < 3, MutR = 1/Nvar; MutShrink = 1; 
   elseif isempty(MutOpt), MutR = 1/Nvar; MutShrink = 1; 
   elseif isnan(MutOpt), MutR = 1/Nvar; MutShrink = 1; 
   else    
      if length(MutOpt) == 1, MutR = MutOpt; MutShrink = 1; 
      elseif length(MutOpt) == 2, MutR = MutOpt(1); MutShrink = MutOpt(2); 
      else, error(' Too many parameter in MutOpt'); end 
   end 
 
   if isempty(MutR), MutR = 1/Nvar; 
   elseif isnan(MutR), MutR = 1/Nvar; 
   elseif length(MutR) ~= 1, error('Parameter for mutation rate must be a scalar'); 
   elseif (MutR < 0 | MutR > 1), error('Parameter for mutation rate must be a scalar in [0, 1]'); end 
 
   if isempty(MutShrink), MutShrink = 1; 
   elseif isnan(MutShrink), MutShrink = 1; 
   elseif length(MutShrink) ~= 1, error('Parameter for shrinking mutation range must be a scalar'); 
   elseif (MutShrink < 0 | MutShrink > 1),  
      error('Parameter for shrinking mutation range must be a scalar in [0, 1]'); 
   end 
      
% the variables are mutated with probability MutR 
% NewChrom = OldChrom (+ or -) * Range * MutShrink * Delta 
% Range = 0.5 * (upperbound - lowerbound) 
% Delta = Sum(Alpha_i * 2^-i) from 0 to ACCUR; Alpha_i = rand(ACCUR,1) < 1/ACCUR 
 
% Matrix with range values for every variable 
   Range = rep(0.5 * MutShrink *(FieldDR(2,:)-FieldDR(1,:)),[Nind 1]); 
 
% zeros and ones for mutate or not this variable, together with Range 
   Range = Range .* (rand(Nind,Nvar) < MutR); 
 
% compute, if + or - sign  
   Range = Range .* (1 - 2 * (rand(Nind,Nvar) < 0.5)); 
 
% used for later computing, here only ones computed 
   ACCUR = 20; 
   Vect = 2 .^ (-(0:(ACCUR-1))'); 
   Delta = (rand(Nind,ACCUR) < 1/ACCUR) * Vect; 
   Delta = rep(Delta, [1 Nvar]); 
 
% perform mutation  
   NewChrom = OldChrom + Range .* Delta; 
 
% Ensure variables boundaries, compare with lower and upper boundaries 
   NewChrom = max(rep(FieldDR(1,:),[Nind 1]), NewChrom); 
   NewChrom = min(rep(FieldDR(2,:),[Nind 1]), NewChrom); 
 
 
% End of function