Stochastic Hill Climbing

Question

I am trying to implement Stoachastic Hill Climbing in Java. I understand that this algorthim makes a new solution which is picked randomly and then accept the solution based on how bad/good it is. For example, if its very bad then it will have a small chance and if its slighlty bad then it will have more chances of being selected but I am not sure how I can implement this probability in java.

Whilst browing on Google, I came across this equation, where;

• f respresent the old fitness
• f' respresent the new fitness
• T is a parameter

I am not really sure how to interpret this equation.

Can someone please help me on how I can implement this in Java?

Answer 1

The left hand side of the equation p will be a double between 0 and 1, inclusively. oldFitness, newFitness and T can also be doubles.

You will have something similar to this in your code:

double p = 1 / (1 + Math.exp((oldFitness - newFitness) / T));
if (Math.random() < p) {
    // accept the new solution