Class: Biopsy::SPEA2

Inherits:
Object
  • Object
show all
Defined in:
lib/biopsy/optimisers/spea2.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(parameter_ranges, threads = 8) ⇒ SPEA2

Returns a new instance of SPEA2.



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# File 'lib/biopsy/optimisers/spea2.rb', line 9

def initialize(parameter_ranges, threads=8)
	@parameter_ranges = parameter_ranges
	@currently_mating = false
	@probability_of_cross = 0.94
	@population_size = 50
	@archive_size = 15
	@mutation_rate = 0.20
	@generation_handler = Generation.new(@population_size, @archive_size)
	@mating_handler = MatingHandler.new(@population_size, @probability_of_cross, @parameter_ranges, @mutation_rate)
end

Instance Attribute Details

#archive_size ⇒ Object

Returns the value of attribute archive_size.



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# File 'lib/biopsy/optimisers/spea2.rb', line 8

def archive_size
  @archive_size
end

#current ⇒ Object (readonly)

Returns the value of attribute current.



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# File 'lib/biopsy/optimisers/spea2.rb', line 6

def current
  @current
end

#population_size ⇒ Object

Returns the value of attribute population_size.



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# File 'lib/biopsy/optimisers/spea2.rb', line 8

def population_size
  @population_size
end

#probability_of_cross ⇒ Object

Returns the value of attribute probability_of_cross.



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# File 'lib/biopsy/optimisers/spea2.rb', line 6

def probability_of_cross
  @probability_of_cross
end

Instance Method Details

#best ⇒ Object 



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# File 'lib/biopsy/optimisers/spea2.rb', line 78

def best
	@best
end

#finished? ⇒ Boolean

check if termination conditions are met

Returns:

  • (Boolean) 


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# File 'lib/biopsy/optimisers/spea2.rb', line 75

def finished?
	true if rand < 0.00025
end

#get_children_to_score(selected_to_mate) ⇒ Object 



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# File 'lib/biopsy/optimisers/spea2.rb', line 44

def get_children_to_score selected_to_mate
	@children_to_score = @mating_handler.run(selected_to_mate)
end

#knows_starting_point? ⇒ Boolean

return true if algorithm knows its own starting point

Returns:

  • (Boolean) 


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# File 'lib/biopsy/optimisers/spea2.rb', line 55

def knows_starting_point?
	return true
end

#random_parameter_set ⇒ Object

generates a random parameter set



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# File 'lib/biopsy/optimisers/spea2.rb', line 71

def random_parameter_set
	Hash[@parameter_ranges.map { |k, v| [k, v.sample] }]
end

#run_one_iteration(parameters, score) ⇒ Object

accepts a parameter set and a score (which are added to population) returns another parameter set to be scored which is then accepted next iteration



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# File 'lib/biopsy/optimisers/spea2.rb', line 25

def run_one_iteration(parameters, score)
	self.run_one_mating_iteration(parameters, score) if @currently_mating == true
  @current = {:parameters => parameters, :score => score}
  # update best score?
  self.update_best?
  # push new parameter set into generation
  @currently_mating = @generation_handler.add_new_individual(@current)
  if @currently_mating == true
  	# begin mating process
  	# empty current population
  	@generation_handler.population_array = []
  	selected_to_mate = @mating_handler.select_mating_population(@generation_handler.archive_array)
  	self.get_children_to_score(selected_to_mate)
  	@children_to_score.pop[:parameters]
  else
  	# get next parameter set to score
  	self.random_parameter_set
  end
end

#run_one_mating_iteration(parameters, score) ⇒ Object 



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# File 'lib/biopsy/optimisers/spea2.rb', line 47

def run_one_mating_iteration(parameters, score)
	@generation_handler.add_new_individual({:parameters => parameters, :score => score})
	if @children_to_score.length == 1
		@currently_mating = false
	end
	@children_to_score.pop
end

#select_starting_point ⇒ Object

returns a parameter set to be used as the starting point



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# File 'lib/biopsy/optimisers/spea2.rb', line 67

def select_starting_point
	self.random_parameter_set
end

#setup(start_point) ⇒ Object 



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# File 'lib/biopsy/optimisers/spea2.rb', line 19

def setup start_point
	@current = {:parameters => start_point, :score => nil}
	@best = @current
end

#update_best? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/biopsy/optimisers/spea2.rb', line 58

def update_best?
  if @best[:score].nil? || @current[:score] > @best[:score]
    @best = @current.clone
    @iterations_since_best = 0
  else
    @iterations_since_best += 1
  end
end