# A container for all the parts of a graph. The graph can have arbitrary attributes,
# treated as method names.
class Graph < OpenStruct
- def initialize
- super
+ def initialize(values = {})
+ super(values)
self.edges = Array.new
self.vertices = Array.new
self
end
self
end
- end
+
+ # Connects two vertices, creating and storing a new edge
+ # Also adds the vertices, unless they're already in the graph
+ def connect(vertex1, vertex2)
+ self.vertices << vertex1 unless self.vertices.include? vertex1
+ self.vertices << vertex2 unless self.vertices.include? vertex2
+ edge = Edge.new
+ self.edges << edge
+ edge << vertex1 << vertex2
+ end
+
+ # Form a product graph of this graph and the other.
+ # Return the product graph.
+ def product(other)
+ product_graph = Graph.new
+ self.vertices.each do |v1|
+ other.vertices.each do |v2|
+ product_graph << Vertex.new({:g1_vertex => v1, :g2_vertex => v2})
+ end
+ end
+ self.edges.each do |e1|
+ e1_vertices = e1.vertices
+ other.edges.each do |e2|
+ e2_vertices = e2.vertices
+ source = product_graph.vertices.find {|v| v.g1_vertex == e1_vertices[0] and v.g2_vertex == e2_vertices[0]}
+ destination = product_graph.vertices.find {|v| v.g1_vertex == e1_vertices[1] and v.g2_vertex == e2_vertices[1]}
+ product_graph.connect source, destination
+ source = product_graph.vertices.find {|v| v.g1_vertex == e1_vertices[0] and v.g2_vertex == e2_vertices[1]}
+ destination = product_graph.vertices.find {|v| v.g1_vertex == e1_vertices[1] and v.g2_vertex == e2_vertices[0]}
+ product_graph.connect source, destination
+ end
+ end
+ product_graph
+ end
+
+
+ def initial_similarity
+ self.vertices.each do |v|
+ if block_given?
+ v.initial_similarity = yield v
+ else
+ v.initial_similarity = 1.0
+ end
+ v.similarity = v.initial_similarity
+ end
+ end
+
+ # Performs similarity flooding on a graph
+ # Assumes that the initial similarity has already been calculated
+ def similarity_flood(opts = {})
+ max_iterations = opts[:iterations] || 100
+ max_residual = opts[:max_residual] || 0.001
+ iteration = 1
+ residual = max_residual + 1
+ while residual > max_residual and iteration <= max_iterations
+ self.vertices.each do |v|
+ v.last_similarity = v.similarity
+ end
+ self.vertices.each do |v|
+ n = v.neighbours.length
+ v.neighbours.each do |neighbour|
+ neighbour.similarity += v.last_similarity / n
+ end
+ end
+ max_similarity = vertices.max {|v, w| v.similarity <=> w.similarity}.similarity
+ self.vertices.each do |v|
+ v.similarity = v.similarity / max_similarity
+ end
+ residual = Math.sqrt(self.vertices.reduce(0) {|a, v| a += (v.similarity - v.last_similarity) ** 2})
+ iteration += 1
+ end
+
+ end
+
+ end # class
end