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mutationgaussian.m

## Copyright (C) 2008 Luca Favatella <slackydeb@gmail.com>
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; If not, see <http://www.gnu.org/licenses/>.

## Author: Luca Favatella <slackydeb@gmail.com>
## Version: 1.7.1

function mutationChildren = \
      mutationgaussian (parents, options, nvars, FitnessFcn,
                        state, thisScore,
                        thisPopulation)
   = \
      __ga_popinitrange__ (options.PopInitRange, nvars);

  ## start mutationgaussian logic
  Scale = options.MutationFcn{1, 2};
  #assert (size (Scale), [1 1]); ## DEBUG
  Shrink = options.MutationFcn{1, 3};
  #assert (size (Shrink), [1 1]); ## DEBUG

  ## initial standard deviation (i.e. when state.Generation == 0)
  tmp_std = Scale * (UB - LB); ## vector = scalar * vector

  ## recursively compute current standard deviation
  for k = 1:state.Generation
    tmp_std(1, 1:nvars) = (1 - Shrink * (k / options.Generations)) * tmp_std;
  endfor
  current_std(1, 1:nvars) = tmp_std;
  nc_parents = columns (parents);
  expanded_current_std(1:nc_parents, 1:nvars) = \
      ones (nc_parents, 1) * current_std;

  ## finally add random numbers
  mutationChildren(1:nc_parents, 1:nvars) = \
      thisPopulation(parents(1, 1:nc_parents), 1:nvars) + \
      expanded_current_std .* randn (nc_parents, nvars);
endfunction

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