Question

I am currently working on a project (TSP) and am attempting to convert some simulated annealing pseudocode into Java. I have been successful in the past at converting pseudocode into Java code, however I am unable to convert this successfully.

The pseudocode is:

T0(T and a lowercase 0)    Starting temperature
Iter    Number of iterations
λ    The cooling rate

1.  Set T = T0 (T and a lowercase 0)
2.  Let x = a random solution
3.  For i = 0 to Iter-1
4.  Let f = fitness of x
5.  Make a small change to x to make x’
6.  Let f’ = fitness of new point
7.  If f’ is worse than f then
8.      Let p = PR(f’, f, Ti (T with a lowercase i))
9.      If p > UR(0,1) then
10.         Undo change (x and f)
11.     Else
12.         Let x = x’
13.     End if
14.     Let Ti(T with a lowercase i) + 1 = λTi(λ and T with a lowercase i)
15. End for
Output:  The solution x

If somebody could show me a basic mark-up of this in Java I would be extremely grateful – I just can’t seem to figure it out!

I am working across multiple classes using a number of functions (which I will not list as it is irrelevant for what I am asking). I already have a smallChange() method and a fitness function – could there be a chance that I would need to create a number of different versions of said methods? For example, I have something like:

public static ArrayList<Integer> smallChange(ArrayList<Integer> solution){

//Code is here.

}

Could I possibly need another version of this method which accepts different parameters? Something along the lines of:

public static double smallChange(double d){

//Code is here.

}

All I require is a basic idea of how this would look when written in Java – I will be able to adapt it to my code once I know what it should look like in the correct syntax, but I cannot seem to get past this particular hurdle.

Answer 1

The basic code should look like this:

public class YourClass {
  public static Solution doYourStuff(double startingTemperature, int numberOfIterations, double coolingRate) {
    double t = startingTemperature;
    Solution x = createRandomSolution();
    double ti = t;

    for (int i = 0; i < numberOfIterations; i ++) {
      double f = calculateFitness(x);
      Solution mutatedX = mutate(x);
      double newF = calculateFitness(mutatedX);
      if (newF < f) {
        double p = PR(); // no idea what you're talking about here
        if (p > UR(0, 1)) { // likewise
          // then do nothing
        } else {
          x = mutatedX;
        }
        ti = t * coolingRate;
      }
    }
    return x;
  }

  static class Solution {
    // no idea what's in here...
  }
}

Now as far as wanting different versions of smallChange() method – totally doable, but you have to read up on inheritance a little bit