Set Maximum Number of Generations
The Generations option in Stopping criteria determines the maximum number of generations the genetic algorithm runs for—see Stopping Conditions for the Algorithm. Increasing the Generations option often improves the final result.
As an example, change the settings in the Optimization app as follows:
Set Fitness function to
@rastriginsfcn.Set Number of variables to
10.Select Best fitness in the Plot functions pane.
Set Generations to
Inf.Set Stall generations to
Inf.Set Stall time limit to
Inf.
Run the genetic algorithm for approximately 300 generations and click Stop. The following figure shows the resulting best fitness plot after 300 generations.
Note that the algorithm stalls at approximately
generation number 170—that is, there is no immediate improvement
in the fitness function after generation 170. If you restore Stall
generations to its default value of 50,
the algorithm could terminate at approximately generation number 220.
If the genetic algorithm stalls repeatedly with the current setting
for Generations, you can try increasing both
the Generations and Stall generations options
to improve your results. However, changing other options might be
more effective.
The command-line options relating to Generations and
Stall generations are MaxGenerations and
MaxStallGenerations, respectively. To run this example at the
command line:
options = optimoptions('ga','MaxGenerations',300,... 'MaxStallGenerations',Inf,'PlotFcn',@gaplotbestf); x = ga(@rastriginsfcn,10,[],[],[],[],[],[],[],options);
Note
When Mutation function is set to Gaussian,
increasing the value of Generations might actually
worsen the final result. This can occur because the Gaussian mutation
function decreases the average amount of mutation in each generation
by a factor that depends on the value specified in Generations.
Consequently, the setting for Generations affects
the behavior of the algorithm.