function [ fitness ] = SGA_FITNESS_function_TSP( path_array , TSP_cost_matrix)
% /*M-FILE FUNCTION SGA_FITNESS_function_TSP MMM SGALAB */ %
% /*==================================================================================================
% Simple Genetic Algorithm Laboratory Toolbox for Matlab 7.x
%
% Copyright 2007 The SxLAB Family - Yi Chen - chenyi2005@gmail.com
% ====================================================================================================
%
%File description:
%
% to define the fitness function for TSP
%
%Input:
% path_code_string -- is the decimal space pool
% TSP_cost_matrix -- TSP_cost_matrix is the cost list given as an
% initial condition ,
% in TSP_cost_matrix:
% a(i,j) is the travelling cost from city i to city j
% (1) if there is no path from city i to city j, a(i,j) = NaN
% (2) if from i to j , a(i,j) = xxx.xx ( > 0 )
% if from j to i , a(i,j) = -xxx.xx ( < 0 ) and a(j,i) = xxx.xx( >0 )
% (3) if i = j , in same city a(i,i) = 0
%Output:
% fitness-- is the fitness value, fitness is to get MAX value
%
%Appendix comments:
%
%Example:
% path_array = [ 2 5 3 4 1]
% TSP_cost_matrix = [ 0 1 1 1 1;
% 1 0 1 1 3;
% 1 1 0 4 1;
% 1 1 1 0 1;
% 1 1 1 1 0;
% ];
% [ fitness ] = SGA_FITNESS_function_TSP( path_array,TSP_cost_matrix )
%
% path_array =
%
% 2 5 3 4 1
%
%
% fitness =
%
% 0.1000
%===================================================================================================
% See Also: SGA_FITNESS_function_TSP ,
% SGA__TSP_cost_evaluating ,
%
%===================================================================================================
%
%===================================================================================================
%Revision -
%Date Name Description of Change email Location
%27-Jun-2003 Chen Yi Initial version chen_yi2000@sina.com Chongqing
%14-Jan-2005 Chen Yi update 1003 chenyi2005@gmail.com Shanghai
%HISTORY$
%==================================================================================================*/
%SGA_FITNESS_function_TSP begin
%User can design their own fitness function here in Matlab style
% get traveling cost
path_cost = SGA__TSP_cost_evaluating( path_array, TSP_cost_matrix );
% fitness is to get max value, and path_cost need min value,
% so we use 1/(cost+eps) , eps is to avoid 1/0
fitness = 1./(path_cost + eps);
%
%SGA_FITNESS_function_TSP end
