Roulette Selection in Genetic Algorithms

Question

Can anyone provide some pseudo code for a roulette selection function? How would I implement this:

Answer 1

This Swift 4 array extension implements weighted random selection, a.k.a Roulette selection from its elements:

public extension Array where Element == Double {

    /// Consider the elements as weight values and return a weighted random selection by index.
    /// a.k.a Roulette wheel selection.
    func weightedRandomIndex() -> Int {
        var selected: Int = 0
        var total: Double = self[0]

        for i in 1..

For example given the two element array:

[0.9, 0.1]

weightedRandomIndex() will return zero 90% of the time and one 10% of the time.

Here is a more complete test:

let weights = [0.1, 0.7, 0.1, 0.1]
var results = [Int:Int]()
let n = 100000
for _ in 0..

output:

0.1 0.09906
0.1 0.10126
0.1 0.09876
0.7 0.70092

This answer is basically the same as Andrew Mao's answer here: https://stackoverflow.com/a/15582983/74975