Module: Util::AlpsIndividual

Included in:
PipedIndividual
Defined in:
../lib/alps_individual.rb

Overview

This class implements a necessary logic for ALPS strategy. See: www.cs.york.ac.uk/rts/docs/GECCO_2006/docs/p815.pdf

Class Method Summary (collapse)

Instance Method Summary (collapse)

Class Method Details

+ (Object) age_gap(gap)

Set the AGE_GAP parameter of the ALPS. Required for AlpsIndividual.age_limits computation. This is the multiplier of the age_limits serie. 



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# File '../lib/alps_individual.rb', line 10

def AlpsIndividual.age_gap gap
  @@age_gap = gap
  @@limits = nil
end

+ (Object) age_limits

Get the age limit for each layer. The result is the AlpsIndividual.aging_scheme serie of the AlpsIndividual.layers length, multiplied by AlpsIndividual.age_gap. 



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# File '../lib/alps_individual.rb', line 36

def AlpsIndividual.age_limits
  return @@limits unless @@limits.nil?

  case @@aging_scheme 

    when :linear
      s = [ 1 ]
      s << s.last + 1 while s.size < @@layers 

    when :fibonacci
      s = [ 1, 2 ] # as defined in the original paper, there is a missing F1=1 member
      s << s.last + s[ s.size-2 ] while s.size < @@layers 

    when :polynomial
      s = []
      (1..@@layers).each { |i| s << i * i }

    when :exponential
      s = []
      (0...@@layers).each { |i| s << 2 ** i }

    else 
      raise "AlpsIndividual: a scheme '#{@@aging_scheme}' not supported"

  end

  return @@limits = s.map { |i| i * @@age_gap }
end

+ (Object) aging_scheme(scheme)

Set the aging scheme parameter. Required for AlpsIndividual.age_limits computation. Allowed values are: 


  :linear .. 1, 2, 3, 4, 5...
  :fibonacci .. 1, 2, 3, 5, 8, 13, 21...
  :polynomial .. 1, 2, 4, 9, 16, 25, 49...
  :exponential .. 1, 2, 4, 8, 16, 32, 64...


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# File '../lib/alps_individual.rb', line 22

def AlpsIndividual.aging_scheme scheme
  @@aging_scheme = scheme
  @@limits = nil     
end

+ (Object) layers(layers)

Set the maximum number of layers (the requred length of the AlpsIndividual.age_limits serie). 



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# File '../lib/alps_individual.rb', line 28

def AlpsIndividual.layers layers
  raise "AlpsIndividual: not enough layers, needed at least 2" if layers < 2
  @@layers = layers
  @@limits = nil     
end

Instance Method Details

- (Object) age

The age of the individual. The newly created one has the age 0. If the genome of the individual is based of the genome(s) of the parent(s), AlpsIndividual#parents method is to be used. 



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# File '../lib/alps_individual.rb', line 69

def age
  @age = 0 unless defined? @age
  @age
end

- (Object) layer

Compute the index of the layer the individual belongs to. The result depends on AlpsIndividual.age_limits and AlpsIndividual#age. 



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# File '../lib/alps_individual.rb', line 85

def layer
  return nil unless defined? @@limits
  AlpsIndividual.age_limits.each_with_index do |max,i|
    return i if self.age <= max
  end
  return @@limits.size
end

- (Object) parents(p1, p2 = nil)

Compute the AlpsIndividual#age of the individual from ages of it’s parent(s). If p1 and p2 are AlpsIndividual parents, the age will be: 


  my.age = 1 + max( p1.age, p2.age )


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# File '../lib/alps_individual.rb', line 78

def parents( p1, p2=nil )
  @age = 1 + ( ( p2.nil? or p1.age > p2.age ) ? p1.age : p2.age )
end