Documentation of reclinex

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Function Synopsis

NewChrom = reclinex(OldChrom, RecOpt, FieldDR);

Help text

 EXtended LINe RECombination

 This function performs extended line recombination between
 pairs of individuals and returns the new individuals after mating.
 The internal working of the function is similar to mutreal.

 Syntax:  NewChrom = reclinex(OldChrom, RecOpt, FieldDR)

 Input parameters:
    OldChrom  - Matrix containing the chromosomes of the old
                population. Each row corresponds to one individual
    RecOpt    - (optional) Vector containing recombination rate and shrink value
                RecOpt(1): MutR - number containing the recombination rate -
                           probability for recombine a pair of parents
                           if omitted or NaN, RecOpt(1) = 1 is assumed
                RecOpt(2): MutShrink - (optional) number for shrinking the
                           recombination range in the range [0 1], possibility to
                           shrink the range of the recombination depending on,
                           for instance actual generation.
                           if omitted or NaN, RecOpt(2) = 1 is assumed
    FieldDR   - Matrix describing the boundaries of each variable.

 Output parameter:
    NewChrom - Matrix containing the chromosomes of the population
               after mating, ready to be mutated and/or evaluated,
               in the same format as OldChrom.

 See also: recombin, recdis, recint, reclin, mutreal, mutbmc

Cross-Reference Information

Listing of function reclinex

%  Author:  Hartmut Pohlheim
%  History: 27.03.95    file created
%           07.08.95    parameter checking shortened
%           12.02.97    file name changed to reclinex
%                          some cleanup


function NewChrom = reclinex(OldChrom, RecOpt, FieldDR);

% Check parameter consistency
   if nargin < 3,  error('Not enough input parameter'); end

   % Identify the population size (Nind) and the number of variables (Nvar)
   [Nind,Nvar] = size(OldChrom);

   % Check size of boundaries
   [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 < 2, RecOpt = []; end
   if isnan(RecOpt), RecOpt = []; end
   if isempty(RecOpt), MutR = 1; MutShrink = 1;
   else   
      if length(RecOpt) == 1, MutR = RecOpt; MutShrink = 1;
      elseif length(RecOpt) == 2, MutR = RecOpt(1); MutShrink = RecOpt(2);
      else, error(' Too many parameter in RecOpt'); end
   end

   if isempty(MutR), MutR = 1;
   elseif length(MutR) ~= 1, error('Parameter for recombination rate must be a scalar');
   elseif (MutR < 0 | MutR > 1), error('Parameter for recombination rate must be a scalar in [0, 1]'); end

   if isempty(MutShrink), MutShrink = 1;
   elseif length(MutShrink) ~= 1, error('Parameter for shrinking recombination range must be a scalar');
   elseif (MutShrink < 0 | MutShrink > 1), 
      error('Parameter for shrinking recombination range must be a scalar in [0, 1]');
   end

% Identify the number of matings
   Xops = floor(Nind/2);

% NewChrom = OldChrom (+ or -) * Range * MutShrink * Delta * ChromDiff
% - with probability 0.9, + with probability 0.1
% Range = 0.5 * (upperbound - lowerbound), given by FieldDR
% Delta = Sum(Alpha_i * 2^-i) from 0 to ACCUR; Alpha_i = rand(ACCUR,1) < 1/ACCUR
% ChromDiff = (individual1 - individual2) / Distance between individuals 

% Matrix with range values for every variable
   Range = repmat(0.1 * MutShrink *(FieldDR(2,:)-FieldDR(1,:)),[Xops 1]);

% zeros and ones for recombine or not this variable, together with Range
   if MutR < 1, Range = Range .* repmat((rand(Xops,1) < MutR), [1 Nvar]); end

% compute, if + or - sign 
   Range = Range .* (1 - 2 * (rand(Xops,Nvar) < 0.9));

% compute distance between mating pairs
   NormO = zeros(Xops,1);
   for irun = 1:Xops,
      NormO(irun) = max(eps, abs(norm(OldChrom(2*irun,:)) - norm(OldChrom(2*irun-1,:))));
   end

% compute difference between variables divided by distance
   ChromDiff = zeros(Xops,Nvar);
   for irun = 1:Xops
      ChromDiff(irun,:) = diff([OldChrom(2*irun-1,:); OldChrom(2*irun,:)]) / NormO(irun);
   end

% compute delta value for all individuals
   ACCUR = 16;
   Vect = 2 .^ (-(0:(ACCUR-1))');
   Delta = (rand(Xops,ACCUR) < 1/ACCUR) * Vect;
   Delta = repmat(Delta, [1 Nvar]);

% Performs recombination
   odd = 1:2:Nind-1;
   even= 2:2:Nind;

   % recombination
   NewChrom(odd,:)  = OldChrom(odd,:)  + Range .* Delta .* (ChromDiff);
   NewChrom(even,:) = OldChrom(even,:) + Range .* Delta .* (-ChromDiff);

% If the number of individuals is odd, the last individual cannot be mated
% but must be included in the new population
   if rem(Nind,2),  NewChrom(Nind,:)=OldChrom(Nind,:); end

% Ensure variables boundaries, compare with lower and upper boundaries
   NewChrom = max(repmat(FieldDR(1,:),[Nind 1]), NewChrom);
   NewChrom = min(repmat(FieldDR(2,:),[Nind 1]), NewChrom);


% End of function