% RECINT.M       (RECombination extended INTermediate)
%
% This function performs extended intermediate recombination between
% pairs of individuals and returns the new individuals after mating.
%
% Syntax:  NewChrom = recint(OldChrom, XOVR)
%
% Input parameters:
%    OldChrom  - Matrix containing the chromosomes of the old
%                population. Each line corresponds to one
%                individual
%    XOVR      - Probability of crossover occurring between pairs
%                of individuals. (not used, only for compatibility)
%
% 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.
%
%  Author:    Hartmut Pohlheim
%  History:   25.11.93     file created
%             06.12.93     change of name of function
%             25.02.94     clean up
%             19.03.94     multipopulation support removed
%             21.01.03     tested under MATLAB v6 by Alex Shenfield

function NewChrom = recint(OldChrom, XOVR);

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

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

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

   % position of value of offspring compared to parents
   Alpha = -0.25 + 1.5 * rand(Xops,Nvar);

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

   % the same ones more for second half of offspring
   Alpha = -0.25 + 1.5 * rand(Xops,Nvar);
   NewChrom(even,:) = OldChrom(odd,:) + Alpha .* (OldChrom(even,:) - OldChrom(odd,:));

% 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

% End of function