Documentation of selection

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Function Synopsis

[SelCh, SUBPOPSel, SelIx] = selection(SEL_F, Chrom, FitnV, GGAP, SUBPOP, SelOpt);

Help text

 high level SELECTion function

 This function is the high level universal selection function. The
 function handles multiple populations and calls the low level
 selection function for the actual selection process.
 Different size of every subpopulation is supported.

 Syntax:  [SelCh, SUBPOPSel, SelIx] = selection(SEL_F, Chrom, FitnV, GGAP, SUBPOP, SelOpt)

 Input parameters:
    SEL_F     - Name of the selection function
    Chrom     - Matrix containing the individuals (parents) of the current
                population. Each row corresponds to one individual.
    FitnV     - Column vector containing the fitness values of the
                individuals in the population.
    GGAP      - (optional) Rate of individuals to be selected
                if omitted 1.0 is assumed
    SUBPOP    - (optional) Vector/scalar containing number of individuals
                per subpopulation/number of subpopulations
                if omitted or NaN, 1 subpopulation is assumed
    SelOpt    - (optional) Vector containing selection paremeters
                SelOpt(1, ...): used in 'sellocal'

 Output parameters:
    SelCh     - Matrix containing the selected individuals.
    SUBPOPSel - Vector containing number of individuals selected per
                subpopulation
    SelIx     - (optional) Column vector containing the indices
                of the selected individuals.

 See also: selrws, selsus, sellocal, seltrunc, reins, reinsloc, migrate, mutate, recombin

Cross-Reference Information

Listing of function selection

% Author:   Hartmut Pohlheim
% History:  10.05.94    file created
%           09.09.94    SelIx as output parameter
%           17.02.95    SelOpt added
%           04.08.95    multi strategy support added
%                       different parameters (SEL_F, SelOpt) per subpopulation
%                       parameter checking shortened
%           29.04.96    call of selection function with eval changed,
%                          made problem with error
%           31.07.96    new format for SUBPOP introduced, vector contains now
%                          number of individuals for every subpopulation
%                       output parameter SUBPOPSel added
%                       ordering of output parameters changed
%           07.03.97    computation of NSel changed, from round to floor
%                          thus, if GGAP is smaller than 1, NSel is definitely
%                          smaller than Nind
%           25.05.99    eval replaced by feval
%                       parameter handling enhanced


function [SelCh, SUBPOPSel, SelIx] = selection(SEL_F, Chrom, FitnV, GGAP, SUBPOP, SelOpt);

% include selection functions for compilation
%#function selsus selrws seltrunc seltour sellocal

% Define default parameters
   GGAPStandard = 1;

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

   % Identify the population size (Nind)
   [NindCh,Nvar] = size(Chrom);
   [NindF,VarF] = size(FitnV);
   if NindCh ~= NindF, error('Number of entires (rows) in Chrom and FitnV disagree'); end
   if VarF ~= 1, error('FitnV must be a column vector'); end
  
   if nargin < 5, SUBPOP = []; end
   SUBPOP = compdiv('checksubpop', SUBPOP, NindCh);
   NumSUBPOP = length(SUBPOP);

   if (size(SEL_F,1) == 1 & NumSUBPOP > 1), SEL_F = repmat(SEL_F, [NumSUBPOP, 1]); end

   if nargin < 4, GGAP = []; end
   if isempty(GGAP), GGAP = NaN; end
   if any(GGAP < 0), warning('At least one generation gap was smaller than 0!'); GGAP = max(0, GGAP); end
   if any(isnan(GGAP)), IxNaN = isnan(GGAP); GGAP(IxNaN) = GGAPStandard; end
   if length(GGAP) == 1, GGAP = repmat(GGAP, [NumSUBPOP, 1]); end

   if nargin < 6, SelOpt = []; end
   if isempty(SelOpt), SelOpt = NaN; end
   if (size(SelOpt,1) == 1 & NumSUBPOP > 1), SelOpt = repmat(SelOpt, [NumSUBPOP, 1]); end


% Select individuals from population
   SelCh = []; SelIx = []; SUBPOPSel = [];
   for irun = 1:NumSUBPOP,
      % Get number of individuals in actual subpopulation
      Nind = SUBPOP(irun);

      % Copy fitness values of actual subpopulation
      FitnVSub = FitnV(sum(SUBPOP(1:irun-1))+1:sum(SUBPOP(1:irun)));

      % Compute number of new individuals (to select)
      NSel = floor(Nind * GGAP(irun));

      % Check and handle for one individual in subpopulation
      if Nind == 1,
         NSel = max(NSel, 1);
         ChrIx = ones(NSel, 1) + sum(SUBPOP(1:irun-1));
         SelCh = [SelCh; repmat(Chrom(ChrIx(1),:),[NSel, 1])];
      else
         NSel = max(NSel, 2);
         ChrIx = feval(deblank(SEL_F(irun,:)), FitnVSub, NSel, SelOpt(irun,:));
         ChrIx = ChrIx + sum(SUBPOP(1:irun-1));
         SelCh = [SelCh; Chrom(ChrIx,:)];
      end

      SelIx = [SelIx; ChrIx];
      SUBPOPSel = [SUBPOPSel; length(ChrIx)];
   end
 

% End of function