Roulette wheel selection algorithm

Question

Can anyone provide some pseudo code for a roulette selection function? How would I implement this: I don't really understand how to read this math notation.I want General algorithm to this.

Answer 1

The other answers seem to be assuming that you are trying to implement a roulette game. I think that you are asking about roulette wheel selection in evolutionary algorithms.

Here is some Java code that implements roulette wheel selection.

Assume you have 10 items to choose from and you choose by generating a random number between 0 and 1. You divide the range 0 to 1 up into ten non-overlapping segments, each proportional to the fitness of one of the ten items. For example, this might look like this:

0 - 0.3 is item 1
0.3 - 0.4 is item 2
0.4 - 0.5 is item 3
0.5 - 0.57 is item 4
0.57 - 0.63 is item 5
0.63 - 0.68 is item 6
0.68 - 0.8 is item 7
0.8 - 0.85 is item 8
0.85 - 0.98 is item 9
0.98 - 1 is item 10

This is your roulette wheel. Your random number between 0 and 1 is your spin. If the random number is 0.46, then the chosen item is item 3. If it's 0.92, then it's item 9.