Module: AssociationItem

Defined in:
lib/rbbt/network/paths.rb

Class Method Summary collapse

Class Method Details

.dijkstra(matches, start_node, end_node = nil, threshold = nil, max_steps = nil, &block) ⇒ Object



159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
# File 'lib/rbbt/network/paths.rb', line 159

def self.dijkstra(matches, start_node, end_node = nil, threshold = nil, max_steps = nil, &block)
  adjacency = {}

  matches.each do |m|
    s, t, undirected = m.split "~"
    next m if s.nil? or t.nil? or s.strip.empty? or t.strip.empty?
    adjacency[s] ||= Set.new
    adjacency[s] << t 
    next unless m.undirected
    adjacency[t] ||= Set.new
    adjacency[t] << s  
  end

  return nil unless adjacency.include? start_node

  active = PriorityQueue.new         
  distances = Hash.new { 1.0 / 0.0 } 
  parents = Hash.new                 

  active[start_node] << 0
  best = 1.0 / 0.0
  found = false
  node_dist_cache = {}

  until active.empty?
    u = active.priorities.first
    distance = active.shift
    distances[u] = distance
    path = Paths.extract_path(parents, start_node, u)
    next if path.length > max_steps if max_steps 
    next if not adjacency.include?(u) or (adjacency[u].nil? or adjacency[u].empty? )
    adjacency[u].each do |v|
      node_dist = node_dist_cache[[u,v]] ||= (block_given? ? block.call(u,v) : 1)
      next if node_dist.nil? or (threshold and node_dist > threshold)
      d = distance + node_dist
      next unless d < distances[v] and d < best # we can't relax this one
      active[v] << d
      distances[v] = d
      parents[v] = u
      if (String === end_node ? end_node == v : end_node.include?(v))
        best = d 
        found = true
      end
    end    
  end

  return nil unless found

  if end_node
    end_node = (end_node & parents.keys).first unless String === end_node
    return nil if not parents.include? end_node
    Paths.extract_path(parents, start_node, end_node)
  else
    parents
  end
end