# File lib/ai4r/neural_network/backpropagation.rb, line 189
      def init_activation_nodes
        @activation_nodes = Array.new(@structure.length) do |n| 
          Array.new(@structure[n], 1.0)
        end
        if not disable_bias
          @activation_nodes[0...-1].each {|layer| layer << 1.0 }
        end
      end