Class: RandomWheelPickStrategy

Inherits:
PickStrategy show all
Defined in:
lib/gimuby/genetic/population/pick_strategy/random_wheel_pick_strategy.rb

Instance Attribute Summary collapse

Attributes inherited from PickStrategy

#pick_proportion

Instance Method Summary collapse

Constructor Details

#initialize ⇒ RandomWheelPickStrategy

Returns a new instance of RandomWheelPickStrategy.



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# File 'lib/gimuby/genetic/population/pick_strategy/random_wheel_pick_strategy.rb', line 5

def initialize
  super
  @random_wheel_probability_reason = 0.7
end

Instance Attribute Details

#random_wheel_probability_reason ⇒ Object

Returns the value of attribute random_wheel_probability_reason.



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# File 'lib/gimuby/genetic/population/pick_strategy/random_wheel_pick_strategy.rb', line 10

def random_wheel_probability_reason
  @random_wheel_probability_reason
end

Instance Method Details

#pick(population) ⇒ Object 



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# File 'lib/gimuby/genetic/population/pick_strategy/random_wheel_pick_strategy.rb', line 12

def pick(population)
  number = get_number_to_pick(population)
  reason = @random_wheel_probability_reason
  solutions = population.solutions
  candidates = solutions.clone
  candidates.sort! do |x, y|
    (population.get_fitness x) <=> (population.get_fitness y)
  end
  picked = []
  begin
    # we use a geometric sequence
    max_of_the_rand = (1 - reason ** candidates.length) / (1 - reason)
    r = rand() * max_of_the_rand
    element = 1
    candidates.each do |solution|
      max_accepted_value = (1 - reason ** element) / (1 - reason)
      element += 1
      if max_accepted_value > r
        picked.push solution
        ind = candidates.index solution
        candidates.slice! ind
        break
      end
    end
  end while picked.length < number
  picked
end