BSF and Dijkstra example and test

[SVN r27553]

test/python/py_dijkstra.py

@@ -0,0 +1,109 @@
+# Copyright 2005 The Trustees of Indiana University.
+
+# Use, modification and distribution is subject to the Boost Software
+# License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
+# http://www.boost.org/LICENSE_1_0.txt)
+
+#  Authors: Douglas Gregor
+#           Andrew Lumsdaine
+
+# Note: this code requires the Boost Graph Library bindings for Python
+# and the priodict module. The latter is part of the Python NMS
+# library (http://pynms.sourceforge.net/).
+
+import bgl
+import priodict
+
+class pqueue(bgl.Digraph.VertexQueue):
+  def __init__(self, distance):
+    bgl.Digraph.VertexQueue.__init__(self)
+    self.Q = priodict.priorityDictionary()
+    self.distance = distance
+  def empty(self):
+    return self.Q == {}
+  def top(self):
+    return self.Q.smallest();
+  def pop(self):
+    del self.Q[self.Q.smallest()]
+  def push(self, x):
+    self.Q[x] = self.distance[x]
+  def update(self, x, v):
+    self.distance[x] = v
+    self.Q[x] = v
+
+class dijkstra_bfs_visitor(bgl.Digraph.BFSVisitor):
+  def __init__(self, Q, weight, distance, predecessor):
+    bgl.Digraph.BFSVisitor.__init__(self)
+    self.Q = Q
+    self.weight = weight
+    self.distance = distance
+    self.predecessor = predecessor
+   
+  def tree_edge(self, e, g):
+    (u, v) = (g.source(e), g.target(e))
+    self.distance[v] = self.distance[u] + self.weight[e]   
+    self.predecessor[v] = u
+
+  def gray_target(self, e, g):
+    (u, v) = (g.source(e), g.target(e))
+    if self.distance[u] + self.weight[e] < self.distance[v]:
+      self.Q.update(v, self.distance[u] + self.weight[e])
+      self.predecessor[v] = u;
+    
+
+g = bgl.Digraph()
+
+# Create vertices in the graph
+name = g.get_vertex_string_map("node_id")
+A = g.add_vertex()
+name[A] = "A"
+B = g.add_vertex()
+name[B] = "B"
+C = g.add_vertex()
+name[C] = "C"
+D = g.add_vertex()
+name[D] = "D"
+E = g.add_vertex()
+name[E] = "E"
+
+# Create (weighted) edges in the graph
+weight = g.get_edge_double_map("weight")
+weight[g.add_edge(A, C)] = 1
+weight[g.add_edge(B, B)] = 2
+weight[g.add_edge(B, D)] = 1
+weight[g.add_edge(B, E)] = 2.5
+weight[g.add_edge(C, B)] = 7
+weight[g.add_edge(C, D)] = 3
+weight[g.add_edge(D, E)] = 1
+weight[g.add_edge(E, A)] = 1
+weight[g.add_edge(E, B)] = 1
+
+# Initialize property maps
+predecessor = {}
+distance = g.get_vertex_double_map("distance_from_A")
+for v in g.vertices:
+  predecessor[v] = v
+  distance[v] = 1e100
+
+# Run breadth-first search to compute shortest paths
+distance[A] = 0
+buf = pqueue(distance)
+
+bgl.breadth_first_search(g, A, buf, 
+                         dijkstra_bfs_visitor(buf,weight,distance,predecessor),
+                         color_map = g.get_vertex_color_map("color"))
+
+class show_relaxed_edges(bgl.Digraph.DijkstraVisitor):
+  def edge_relaxed(self, e, g):
+    text = "Relaxed edge (" + name[g.source(e)] + ", " + name[g.target(e)] + ")"
+    print text
+
+# Run Dijkstra's algorithm to compute shortest paths
+distance2 = g.get_vertex_double_map("distance_from_A_also");
+bgl.dijkstra_shortest_paths(g, A, distance_map = distance2, 
+                            visitor=show_relaxed_edges());
+                               
+# Emit graph
+g.write_graphviz("dijkstra-example.dot")
+
+