# File lib/ai4r/neural_network/hopfield.rb, line 99
      def propagate
        sum = 0
        i = (rand * @nodes.length).floor
        @nodes.each_with_index {|node, j| sum += read_weight(i,j)*node }
        @nodes[i] = (sum > @threshold) ? @active_node_value : @inactive_node_value
      end