initializega.m

对遗传算法中产生初始种群进行了详尽的描述

function [pop] = initializega(num, bounds, evalFN,evalOps,options) %有5个输入项，1个输出项
% function [pop]=initializega(populationSize, variableBounds,evalFN,
%                           evalOps,options)
%    initializega creates a matrix of random numbers with 
%    a number of rows equal to the populationSize and a number
%    columns equal to the number of rows in bounds plus 1 for
%    the f(x) value which is found by applying the evalFN.
%    This is used by the ga to create the population if it
%    is not supplied.
%
% pop            - the initial, evaluated, random population 
% populatoinSize - the size of the population, i.e. the number to create
% variableBounds - a matrix which contains the bounds of each variable, i.e.
%                  [var1_high var1_low; var2_high var2_low; ....]
% evalFN         - the evaluation fn, usually the name of the .m file for 
%                  evaluation
% evalOps        - any options to be passed to the eval function defaults []
% options        - options to the initialize function, ie. 
%                  [type prec] where eps is the epsilon value 
%                  and the second option is 1 for float and 0 for binary, 
%                  prec is the precision of the variables defaults [1e-6 1]

% Binary and Real-Valued Simulation Evolution for Matlab GAOT V2 
% Copyright (C) 1998 C.R. Houck, J.A. Joines, M.G. Kay 
%
% C.R. Houck, J.Joines, and M.Kay. A genetic algorithm for function
% optimization: A Matlab implementation. ACM Transactions on Mathmatical
% Software, Submitted 1996.
%
% 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 1, 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. A copy of the GNU 
% General Public License can be obtained from the 
% Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

if nargin<5  %nargin:是用来判断输入项个数的函数
  options=[1e-6 1]; %如果初始化函数的输入项个数小于5，则参数结构体options=[1e-6 1]
end
if nargin<4 %如果初始化函数的输入项个数小于4，则传递给适应度函数的参数evalOps=[]
  evalOps=[];     
end

if any(evalFN<48) %Not a .m file 意思是说如果evalFN不是一个M文件
  if options(2)==1 %Float GA
    estr=['x=pop(i,1); pop(i,xZomeLength)=', evalFN ';'];  
  else %Binary GA
    estr=['x=b2f(pop(i,:),bounds,bits); pop(i,xZomeLength)=', evalFN ';']; 
  end
else %A .m file 如果是M文件
    if options(2)==1 %Float GA 如果options的第二列为1，则采用实数编码
        estr=['[ pop(i,:) pop(i,xZomeLength)]=' evalFN '(pop(i,:),[0 evalOps]);']; %实际上就是和适应度函数衔接了。'[ pop(i,:) pop(i,xZomeLength)]=' evalFN '(pop(i,:),[0 evalOps]);'的格式和适应度函数的定义的格式是一摸一样。
    else %Binary GA 如果参数结构体的第二列为0，则采用二进制编码
        estr=['x=b2f(pop(i,:),bounds,bits);[x v]=' evalFN ...
            '(x,[0 evalOps]); pop(i,:)=[f2b(x,bounds,bits) v];'];  
    end
end

numVars     = size(bounds,1); 		%求出变量的个数，size(bb,1)返回的是bb的行（第一维）的数量。size(bb,2)返回的是bb的列(第二维)的数量。[a, b]=size(A)返回A的行和列数。
rng         = (bounds(:,2)-bounds(:,1))'; %The variable ranges','代表的是对矩阵进行转置。这句程序的意思是确定变量的范围

if options(2)==1 %Float GA 如果浮点编码
  xZomeLength = numVars+1; 		%Length of string is numVar + fit 生成的初始个体的长度等于变量的个数加上1（即含有一个适应度）
  pop         = zeros(num,xZomeLength); 	%Allocate the new population分配新矩阵，num为初始种群的个数
  pop(:,1:numVars)=(ones(num,1)*rng).*(rand(num,numVars))+...
    (ones(num,1)*bounds(:,1)');%生成初始种群各变量的初始值
else %Binary GA
  bits=calcbits(bounds,options(1));
  xZomeLength = sum(bits)+1; 		% Length of string is numVar + fit
  pop = round(rand(num,sum(bits)+1));
end

for i=1:num
  eval(estr);%eval将字符串作为表达式执行,此句程序用来计算适应度值，并且完成全部的pop返回。实际上是eval（['[ pop(i,:) pop(i,xZomeLength)]=' evalFN '(pop(i,:),[0 evalOps]);'];），生成最终的pop。pop(i,:),[0 evalOps]，这一部分实际上是evalFN的输入参数。
end