Java Fitness Function Not Working

Question

I have a fitness function as part of a lab and wish to apply it to a set of 'weights' (ArrayList weights). I have created the array and stored some values in it. I have created random binary strings (which have an 'x' at the end in order to generate random values) which I wish to also apply the fitness function to; however, the problem I am having is that the fitness function always returns a value of 0. Am I missing something here?

The fitness function is as follows:

public static double scalesFitness(ArrayList<Double> weights){  
    if (scasol.length() > weights.size()) return(-1);
    double lhs = 0.0,rhs = 0.0;

    double L = 0.0;
    double R = 0.0;

    for(int i = 0; i < scasol.length(); i++){
        if(scasol.charAt(i) == '0'){
        L = L += 0;
    }
    else if(scasol.charAt(i) == '1'){
        R = R += 1;
    }
    }//end for

    int n = scasol.length();

    return(L-R);

}

Random binary string method:

private static String RandomBinaryString(int n){
    String s = new String();

    for(int i = 0; i <= n; i++){
        int y = CS2004.UI(0,1);
            if(y == 0){
                System.out.print(s + '0');
            }
            else if(y == 1){
                System.out.print(s + '1');
            }
    }

    return(s);
}

Main method (in separate class):

public static void main(String args[]){

    for(int i = 0; i < 10; i++){
        ScalesSolution s = new ScalesSolution("10101x");
        s.println();
    }

    ArrayList<Double> weights = new ArrayList<Double>();

        weights.add(1.0);
        weights.add(2.0);
        weights.add(3.0);
        weights.add(4.0);
        weights.add(10.0);
        System.out.println();

    System.out.print("Fitness: ");
    System.out.print(ScalesSolution.scalesFitness(weights));
}

Once run, the random binary strings work perfectly well, yet the fitness function fails to change from 0. Here is a sample output:

1101100
1100111
0001111
1001010
1110000
0011111
1100111
1011001
0000110
1000000

Fitness: 0.0

If you wish to code for the whole class(es), then please let me know.

Thank you all so much for your time.

Mick.

If this is homework, you should include the homework tag. – Greg Mar 14 '11 at 20:02 — Greg, Mar 14 '11 at 20:02

DHall · Accepted Answer · 2011-03-14T20:10:33.403

2

Looks to me like you're always returning a blank String from RandomBinaryString() - you print out some digits but never actually append them. Use s = s+'0', or s += '0', or s.concat("0") ,or use a StringBuilder , etc...

I'm assuming scasol is your binary string, so that's empty, then nothing in your for loop gets called once, so L and R both stay at 0.0, and you wind up returning 0.0.

edited Mar 14 '11 at 20:10

answered Mar 14 '11 at 20:04

DHall

393
2
13

Thank you, I tried this but it doesn't seem to work. Yes, scasol is my binary String. I have noticed that if I change the following to < from >, it produces -1.0 every time instead of 0.0. `public static double scalesFitness(ArrayList weights) { if (scasol.length() > weights.size()) return(-1);` Could this be affecting it somehow? – Mus Mar 14 '11 at 20:11
@Mick - getting -1 in this case makes sense if scasol is a blank String. Can you post the code for the ScalesSolution constructor? – DHall Mar 14 '11 at 20:15
I just realized `s.concat("0")` by itself won't do anything. Make sure you're assigning the value to s with either `s=s+'0'` or `s+='0'` or `s=s.concat("0")`. The rest of the code should work, also make sure you have the same number of numbers in the Weights list as characters in the seed String. – DHall Mar 14 '11 at 20:43
I tried all of your suggestions but unfortunately they did not seem to work - there must be something else responsible for the lack of function...thank you once again for your effort, I appreciate it; unfortunately, however, I am still nonethewiser as to what it could be...do you happen to have any other suggestions? – Mus Mar 14 '11 at 22:35

score 0 · Answer 2 · answered Mar 14 '11 at 20:05

Your random string RandomBinaryString only ever prints 's' it never alters it so the sum of the function is equivalent to returning 'new String()'.

Another issue, 'L = L += 0' is redundant. It is the same as L = 0. Always.

'R = R+=1' is also redundant, it is the same as R += 1.

score 0 · Answer 3 · answered Mar 14 '11 at 20:23

@DHall Code for scasol constructor:

public ScalesSolution(String s)
{
    boolean ok = true;
    int n = s.length();
    for(int i=0;i<n;++i)
    {
        char si = s.charAt(i);
        if (si != '0' && si != '1') ok = false;
    }
    if (ok)
    {
        scasol = s;
    }
    else
    {
        scasol = RandomBinaryString(n);
    }
}

If this is not of help I can post the code for the class up.

Thanks.

Mick.

Java Fitness Function Not Working

3 Answers3