Hi Márcio,

Try moving the your assignment of the 'performances' variable inside your MyIndividual.setup() method.

It's hard to know without seeing your code, but I suspect that every individual in your population is actually storing a reference to the same instance of 'Measures'.  This line is only called when the MyIndividual constructor is called:

private Measures performances = new Measures();
But when ECJ creates the initial population, it only uses the default constructor of your Individual once, to initialize a "prototype" instance of the Individual.  The population itself is created by cloning this prototype individual and then calling setup() on the clones.

So, to initialize a new Measures object for each clone, you either need to do it in the setup() method, or override MyIndividual.clone() to perform a deep copy.  Using setup() is cleaner, though, since it follows ECJ's convention, and you don't actually care about copying the data.


On Mon, Jan 29, 2018 at 9:11 AM, Márcio Basgalupp <[log in to unmask]> wrote:
Hi all.

When running NSGA-II, I'm having a problem when extending the
Individual class. I create a new class called Measures, when I have
some attributes of performance such as accuracy, fmeasure, etc. My
Individual class (called myIndividual.java) has an object fro this
Measures class (the attribute calls performances). It is a private
attribute, and to get this I need to use individual.getPerformances().

public myIndividual () {

private Measures performances = new Measures();



At the end of the evolution, I get the paretoFront and it is very
weird because if I get, for example,
individual.getPerformance.getAccuracy(), the value is completely
wrong. Just to make sure, I added an attribute called accuracy
directly in myIndividual class, as below.

public myIndividual () {

private double accuracy;
private Measures performances = new Measures();
   void testMethod() {
      accuracy = 0.8;

I assign the same value to both (as in testMethod()), but when I print
it in my Main class (when I have the paretoFront), these values are
different. The value accuracy attribute is correct, but the one in
performances.getAccuracy() is completely wrong.

Should I make some additional thing to fix it? I tried to make
Measures implements Serializable and Clonable, but it didn't work. It
is possible to add into myIndividual.java all attributes on
Measures.java, but I would not like to do it because it must have a
way to fix it correctly.


Prof. Márcio Porto Basgalupp
Instituto de Ciência e Tecnologia (ICT)
Universidade Federal de São Paulo (UNIFESP)


Ph.D student in Computer Science, George Mason University
Web Director, Journal of Mason Graduate Research