Class: Biopsy::Hood

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

Overview

a Hood represents the neighbourhood of a specific location in the parameter space being explored. It is generated using the set of Distributions, which together define the neighbourhood structure.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(distributions, max_size, tabu) ⇒ Hood

Returns a new instance of Hood.



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# File 'lib/biopsy/optimisers/tabu_search.rb', line 91

def initialize(distributions, max_size, tabu)
  # tabu
  @tabu = tabu 
  # neighbourhood
  @max_size = max_size
  @members = []
  @best = {
    :parameters => nil,
    :score => 0.0
  }
  # probabilities
  @distributions = distributions
  self.populate
end

Instance Attribute Details

#best ⇒ Object (readonly)

Returns the value of attribute best.



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# File 'lib/biopsy/optimisers/tabu_search.rb', line 89

def best
  @best
end

Instance Method Details

#generate_neighbour ⇒ Object

generate a single neighbour



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# File 'lib/biopsy/optimisers/tabu_search.rb', line 107

def generate_neighbour
  n = 0
  begin
    if n >= 100
      # taking too long to generate a neighbour, 
      # loosen the neighbourhood structure so we explore further
      # debug("loosening distributions")
      @distributions.each do |param, dist|
        dist.loosen
      end
    end
    # preform the probabilistic step move for each parameter
    neighbour = Hash[@distributions.map { |param, dist| [param, dist.draw] }]
    n += 1
  end while self.is_tabu?(neighbour)
  @tabu << neighbour
  @members << neighbour
end

#is_tabu?(location) ⇒ Boolean

true if location is tabu

Returns:

  • (Boolean) 


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# File 'lib/biopsy/optimisers/tabu_search.rb', line 132

def is_tabu? location
  @tabu.member? location
end

#last? ⇒ Boolean

returns true if the current neighbour is the last one in the Hood

Returns:

  • (Boolean) 


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# File 'lib/biopsy/optimisers/tabu_search.rb', line 150

def last?
  @members.empty?
end

#next ⇒ Object

return the next neighbour from this Hood



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# File 'lib/biopsy/optimisers/tabu_search.rb', line 144

def next
  @members.pop
end

#populate ⇒ Object

generate the population of neighbours



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# File 'lib/biopsy/optimisers/tabu_search.rb', line 137

def populate
  @max_size.times do |i|
    self.generate_neighbour
  end
end

#update_best?(current) ⇒ Boolean

update best?

Returns:

  • (Boolean) 


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# File 'lib/biopsy/optimisers/tabu_search.rb', line 127

def update_best? current
  @best = current.clone if current[:score] > @best[:score]
end