Class: GeneticAlgorithms::RouletteWheel

Inherits:
Object
  • Object
show all
Defined in:
lib/genetic_algorithms/roulette_wheel.rb

Instance Method Summary collapse

Constructor Details

#initialize(chromosomes_and_scores) ⇒ RouletteWheel

Returns a new instance of RouletteWheel.



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# File 'lib/genetic_algorithms/roulette_wheel.rb', line 5

def initialize chromosomes_and_scores
  chromosomes_and_scores  = NaturalHash[ chromosomes_and_scores ]
  total                   = chromosomes_and_scores.values.inject(:+)
  @logger                 = Logging.logger[self]

  normalized = chromosomes_and_scores.map do |chromosome, score| 
    [chromosome, score.to_f/total]
  end

  @normalized = normalized.sort_by { |chromosome, probability| probability }
end

Instance Method Details

#spin ⇒ Object

TODO: use inject here instead of each_pair



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# File 'lib/genetic_algorithms/roulette_wheel.rb', line 18

def spin 
  accumulator, prn = 0, rand

  @normalized.each_pair do |chromosome, probability| 
    if prn <= probability + accumulator
      @logger.debug "Choosing #{chromosome} with probability #{probability}"
      return chromosome 
    end

    accumulator += probability
  end
end