How to make/create a fitness/objective function for GA problem

hello,

how do we define , or how do we make a fitness/objective function that match with our problem in GA? Are there any specific rules?

there are many fitness/objective function such as rastrigin function, ackley, griewank etc. But what if we want to use our own function? How do we create it? Based on what?

Answer 1

[Gavin]

I have a bit of experience in this! I developed a fitness function for an extremely specific problem. In fact, I coded my own specific GA to work on a particular problem with a specific set of variables.

What sort of GA are you intending to use? The MATLAB builtin one?

What is your problem optimising, and what are the design variables?

Gav

[Rudi Martin]

Thanx for your response sir, my problem is actually very simple.

yes... I'm using matlab for my GA problem, but i dont know how to make my own fitness function.

It's about welding optimization. I have three parameters (design variables), each has a different limitation :

Current : 80 100 ampere

Voltage : 80 - 90 volt

Weld time : 13 - 15 second

thank you

[Alan Weiss]

You might be interested in a welding example in the documentation.

Alan Weiss

MATLAB mathematical toolbox documentation

Answer 2

[Shashank Prasanna]

I would start with the documentation to see how to write your own objective/fitness function in MATLAB. This is however a step that comes after you already have your fitness function on paper or know what it is.

There are some examples on how to MATLAB them in MATLAB:

http://www.mathworks.com/help/optim/ug/writing-objective-functions.html#brhkghv-4

Also scroll down to see some example on how these fitness functions were created:

http://www.mathworks.com/help/gads/ga.html

That being said, you will have to come up with you specific fitness function, and GA can help find the parameters that minimize it.