genetic algorithm simple problem

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Phoenix98
Phoenix98 2018-12-10
评论： Walter Roberson 2018-12-10
Hello ,
I have a simple problem to solve with the genetic algorithm in matlab
The fitness function is
that subject to
My question is how to apply these in matlab ga function?
  2 个评论
Mark Sherstan
Mark Sherstan 2018-12-10
编辑：Mark Sherstan 2018-12-10
Look at this example here and then let us know if there is still need for clarification.
Phoenix98
Phoenix98 2018-12-10
Hi , I read it
but how to set the bounds lb and ub according to my problem?
below is the code with the fitness function
function y = fitness(x)
y = (3*x(1) + x(2) - 2*x(3)+0.8 \ 2*x(1)-x(2)+x(3)) + (4*x(1) -2*x(2)+x(3) \ 7*x(1)+3*x(2)-x(3));
% The main program
rng default
FitnessFunction = @fitness;
numberOfVariables = 3;
lb = [-1,-1];
ub = [0,0];
[x,fval] = ga(FitnessFunction,numberOfVariables,[],[],[],[],lb,ub);

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回答（1 个）

Walter Roberson
Walter Roberson 2018-12-10
The item says 0 <= xi, i = 1, 2, 3. Therefore the entries are nonnegative. lb would be [0 0 0]. ub can be left empty or can be set to [inf inf inf]
  2 个评论
Phoenix98
Phoenix98 2018-12-10
Hi,
i tried these values and the f(x) in the solution equal to 2.471428 with x1=1,x2=0,x3=0 not equal to the matlab solution -2.190310
Walter Roberson
Walter Roberson 2018-12-10
So? You are using ga and ga only tries to find a global minima.
Besides, you are not implementing the formula you were given. In MATLAB,
(3*x(1) + x(2) - 2*x(3)+0.8 \ 2*x(1)-x(2)+x(3))
is the same as
((3*x(1)) + x(2) - (2*x(3)) + ((0.8 \ 2) * x(1)) - x(2) + x(3))
which is the same as
((3*x(1)) + x(2) - (2*x(3)) + ((0.8 / 2) * x(1)) - x(2) + x(3))
The form
first sequence \ second sequence
is not the same as
(first sequence) / (second sequence)

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