add linear assignment api python example

python/linear_assignment_api.py

@@ -0,0 +1,66 @@
+# Copyright 2010-2011 Google
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Test linear sum assignment on a 4x4 matrix.
+
+   Example taken from:
+   http://www.ee.oulu.fi/~mpa/matreng/eem1_2-1.htm with kCost[0][1]
+   modified so the optimum solution is unique.
+"""
+
+
+
+from google.apputils import app
+from graph import pywrapgraph
+
+
+def RunAssignmentOn4x4Matrix(forward_graph):
+  """Test linear sum assignment on a 4x4 matrix.
+
+  Arguments:
+    forward_graph: if true uses a ForwardStarGraph or a StarGraph to model
+                   the assignment problem.
+  """
+  num_sources = 4
+  num_targets = 4
+  cost = [[90, 76, 75, 80],
+          [35, 85, 55, 65],
+          [125, 95, 90, 105],
+          [45, 110, 95, 115]]
+  expected_cost = cost[0][3] + cost[1][2] + cost[2][1] + cost[3][0]
+
+  if forward_graph:
+    graph = pywrapgraph.ForwardStarGraph(num_sources + num_targets,
+                                         num_sources * num_targets)
+    assignment = pywrapgraph.ForwardEbertLinearSumAssignment(graph, num_sources)
+  else:
+    graph = pywrapgraph.StarGraph(num_sources + num_targets,
+                                  num_sources * num_targets)
+    assignment = pywrapgraph.EbertLinearSumAssignment(graph, num_sources)
+
+  for source in range (0, num_sources):
+    for target in range(0, num_targets):
+      arc = graph.AddArc(source, num_sources + target)
+      assignment.SetArcCost(arc, cost[source][target])
+
+  assignment.ComputeAssignment()
+  total_cost = assignment.GetCost()
+  print 'total cost', total_cost, '/', expected_cost
+
+
+def main(unused_argv):
+  RunAssignmentOn4x4Matrix(True)
+  RunAssignmentOn4x4Matrix(False)
+
+if __name__ == '__main__':
+  app.run()