Performing a Genetic Algorithm Optimization

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Calling the Function ga at the Command Line Using the Optimization Tool

Calling the Function ga at the Command Line

To use the genetic algorithm at the command line, call the genetic algorithm function ga with the syntax

[x fval] = ga(@fitnessfun, nvars, options)

where

• @fitnessfun is a handle to the fitness function.

• nvars is the number of independent variables for the fitness function.

• options is a structure containing options for the genetic algorithm. If you do not pass in this argument, ga uses its default options.

The results are given by

• x — Point at which the final value is attained

• fval — Final value of the fitness function

Using the function ga is convenient if you want to

• Return results directly to the MATLAB workspace

• Run the genetic algorithm multiple times with different options, by calling ga from a file

Using the Genetic Algorithm from the Command Line provides a detailed description of using the function ga and creating the options structure.

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Using the Optimization Tool

To open the Optimization Tool, enter

optimtool('ga')

at the command line, or enter optimtool and then choose ga from the Solver menu.

You can also start the tool from the MATLAB Start menu as pictured:

To use the Optimization Tool, you must first enter the following information:

• Fitness function — The objective function you want to minimize. Enter the fitness function in the form @fitnessfun, where fitnessfun.m is a file that computes the fitness function. Computing Objective Functions explains how write this file. The @ sign creates a function handle to fitnessfun.

• Number of variables — The length of the input vector to the fitness function. For the function my_fun described in Computing Objective Functions, you would enter 2.

You can enter constraints or a nonlinear constraint function for the problem in the Constraints pane. If the problem is unconstrained, leave these fields blank.

To run the genetic algorithm, click the Start button. The tool displays the results of the optimization in the Run solver and view results pane.

You can change the options for the genetic algorithm in the Options pane. To view the options in one of the categories listed in the pane, click the + sign next to it.

For more information,

• See the Graphical Optimization Tool chapter in the Optimization Toolbox documentation.

• See Example: Rastrigin's Function for an example of using the tool.

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What Is the Genetic Algorithm?

Example: Rastrigin's Function

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