ga

Hello! I have a function:

function z=my_fun(x)
a=2;
b=3;
c=1;
z=a*x(1)-b*x(2)+c*x(3);

I use the genetic algoritm (ga, gatool) to generate input parameters x(1), x(2) and x(3). It is necessary for me, that x(1)<x(2)<x(3). How and where can I set this constraint? Thank you very much for any answer :)

Natalia

Answer 1

[Sean de Wolski]

Interesting idea. This should be possible, probably with non-linear constraint option.

However, (disclaimer: this is just a thought/curiosity, no guarantees at all), what if you just sort x at the beginning of my_fun()? This would enforce the constraint in your fitness function and possibly cause convergence of the guesses. Let me know if/how it works for you.

function z=my_fun(x)
x = sort(x);
a=2;
b=3;
c=1;
z=a*x(1)-b*x(2)+c*x(3);

[Natalia]

Yes, it works. But if I have more input parameters and more constraints (for example: x(1)<x(2)<x(3), x(5)<x(4)<x(1)) sort will not help.

I think it linear constraint (this is just a thought/curiosity too).

If x(1)<x(2)<x(3)

hence:

x(1)<x(2);

x(2)<x(3);

x(1)<x(3);

hence:

1*x(1)-1*x(2)+0*x(3)<0;

0*x(1)+1*x(2)-1*x(3)<0;

1*x(1)+0*x(2)-1*x(3)<0;

If A*x<b,

hence:

A=[1 -1 0; 0 1 -1; 1 0 -1]

b=[0;0;0]

I try to use it. And it works... What do you think about it?

[Sean de Wolski]

Yes, that looks good, I guess it is a linear constraint.