Class: Jinni::Genepool

Inherits:
Array
  • Object
show all
Defined in:
lib/jinni/genepool.rb

Instance Method Summary collapse

Instance Method Details

#average(quality = :fitness) ⇒ Object

this method returns the mean of one quality through a collection of objects. It’s very useful for watching your generations increase in fitness.



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# File 'lib/jinni/genepool.rb', line 50

def average(quality = :fitness)
  self.map {|f| f.send(quality)}.inject{ |sum, n| sum + n }.to_f / self.length
end

#generate(n, mutationRate = 0.01, quality = :fitness) ⇒ Object

use this method to create a new generation of ‘n` creatures based on a genepool. it uses weighted roulette wheel selection to simulate the effects of genetic fitness, then crosses the selected objects together.



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# File 'lib/jinni/genepool.rb', line 32

def generate(n, mutationRate = 0.01, quality = :fitness)
  scratch = self.clone

  pool = scratch.roulette(n * 2, quality)

  generation = Jinni::Genepool.new

  pool.each_slice(2) do |pair|
    child = pair[0] << pair[1]
    (child = child.mutate) if mutationRate > 0
    generation << child
  end

  return generation
end

#roulette(n, quality = :fitness) ⇒ Object

this utility method uses weighted roulette wheel selection to choose ‘n` objects from your gene pool influenced by fitness. It does not cross them.



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# File 'lib/jinni/genepool.rb', line 6

def roulette(n, quality = :fitness)
  scratch = self.clone

  probabilities = scratch.map { |creature| creature.send(quality) }
  selected = []

  n.times do
    r, inc = rand * probabilities.max, 0 # pick a random number and select the  individual
                     # corresponding to that roulette-wheel area
    scratch.each_index do |i|
      if r < (inc += probabilities[i])
        selected << scratch[i]
        # make selection not pick sample twice
        # scratch.delete_at i
        # probabilities.delete_at i
        break
      end
    end
  end
  return selected
end