#44 How to evaluate the performance of a multi-objective genetic algorithm?

[ahmad]

I am trying to evaluate the performance of multi-objective genetic algorithm using NSGA III. I am trying to use The Instrumenter I wrote the following code:

Instrumenter instrumenter=new Instrumenter()
.withProblem("Optimization_Problem")
.withFrequency(100)
.attachAll();
NondominatedPopulation result = new Executor()
.withProblem("Optimization_Problem")
.withAlgorithm("NSGAIII")
.withMaxEvaluations(50000)
.withInstrumenter(instrumenter)
.run();
Accumulator accumulator=instrumenter.getLastAccumulator();
for(int i=0;i<accumulator.size("NFE"); i++){
System.out.println(accumulator.get("NFE",i)+"/t"+accumulator.get(????))
}

But I am little confused on how to continue I think to evaluate the convergence speed of each objective function " i.e. get the mean of each objective function at each generation" but I am a little confused if the instrumenter Can be used to do this what you suggest guys?

Your help is highly appreciated

[Anonymous]

The instrumenter is useful for collecting performance metrics. There are a bunch built in, such as generational distance, hypervolume, etc. You can also define your own custom collector, such as:

import org.moeaframework.core.Algorithm;
import org.moeaframework.core.EpsilonBoxDominanceArchive;
import org.moeaframework.core.Indicator;
import org.moeaframework.core.NondominatedPopulation;

public class CustomCollector implements Collector {

    private final Algorithm algorithm;

    public CustomCollector(Algorithm algorithm) {
        super();
        this.algorithm = algorithm;
    }

    @Override
    public void collect(Accumulator accumulator) {
        NondominatedPopulation result = algorithm.getResult();

        // compute your convergence metric

        accumulator.add("My Convergence Metric", value);
    }

    @Override
    public AttachPoint getAttachPoint() {
        return AttachPoint.isSubclass(Algorithm.class).and(
                AttachPoint.not(AttachPoint.isNestedIn(Algorithm.class)));
    }

    @Override
    public Collector attach(Object object) {
        return new CustomCollector((Algorithm)object);
    }

}

Then attach it with your instrumenter: new Instrumenter().attach(new CustomCollector(null)).

Since you are using NSGA-III, I would encourage you to use the latest code at https://github.com/MOEAFramework/MOEAFramework. We have made a number of enhancements, including better default values for NSGA-III's parameters.