Contents

module Picky

  module Query

    # Calculates weights for certain combinations.
    #
    class Weights # :nodoc:all

      attr_reader :weights

      delegate :empty?, :to => :weights

      #
      #
      def initialize weights = {}
        @weights = weights
      end

      # Get the weight of an allocation.
      #
      def weight_for clustered
        @weights[clustered] || 0
      end

      # Returns an energy term E for allocation. this turns into a probability
      # by P(allocation) = 1/Z * exp (-1/T * E(allocation)),
      # where Z is the normalizing partition function
      # sum_allocations exp(-1/T *E(allocation)), and T is a temperature constant.
      # If T is high the distribution will be close to equally distributed.
      # If T is low, the distribution will be the indicator function
      # for min (E(allocation))…
      #
      # ...
      #
      # Just kidding. It's far more complicated than that. Ha ha ha ha ;)
      #
      # Note: Cache this if more complicated weighings become necessary.
      #
      def score combinations
        # TODO Or it could use actual combinations? Could it? Or make combinations comparable to Symbols.
        #
        weight_for combinations.map(&:category_name).clustered_uniq_fast
      end

      def == other
        @weights == other.weights
      end

      # Prints out a nice representation of the configured weights.
      #
      def to_s
        "#{self.class}(#{@weights})"
      end

    end
  end

end

Version data entries

5 entries across 5 versions & 1 rubygems

Version	Path
picky-3.0.0.pre5	lib/picky/query/weights.rb
picky-3.0.0.pre4	lib/picky/query/weights.rb
picky-3.0.0.pre3	lib/picky/query/weights.rb
picky-3.0.0.pre2	lib/picky/query/weights.rb
picky-3.0.0.pre1	lib/picky/query/weights.rb