214 lines
7.7 KiB
Python
Executable File
214 lines
7.7 KiB
Python
Executable File
#!/usr/bin/env python3
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# Copyright 2010-2025 Google LLC
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# [START program]
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"""Simple Vehicles Routing Problem (VRP).
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This is a sample using the routing library python wrapper to solve a VRP
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problem.
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The solver stop after improving its solution 15 times or after 5 seconds.
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Distances are in meters.
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"""
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# [START import]
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import weakref
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from ortools.constraint_solver import routing_enums_pb2
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from ortools.constraint_solver import pywrapcp
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# [END import]
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# [START data_model]
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def create_data_model():
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"""Stores the data for the problem."""
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data = {}
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data["distance_matrix"] = [
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# fmt: off
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[0, 548, 776, 696, 582, 274, 502, 194, 308, 194, 536, 502, 388, 354, 468, 776, 662],
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[548, 0, 684, 308, 194, 502, 730, 354, 696, 742, 1084, 594, 480, 674, 1016, 868, 1210],
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[776, 684, 0, 992, 878, 502, 274, 810, 468, 742, 400, 1278, 1164, 1130, 788, 1552, 754],
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[696, 308, 992, 0, 114, 650, 878, 502, 844, 890, 1232, 514, 628, 822, 1164, 560, 1358],
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[582, 194, 878, 114, 0, 536, 764, 388, 730, 776, 1118, 400, 514, 708, 1050, 674, 1244],
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[274, 502, 502, 650, 536, 0, 228, 308, 194, 240, 582, 776, 662, 628, 514, 1050, 708],
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[502, 730, 274, 878, 764, 228, 0, 536, 194, 468, 354, 1004, 890, 856, 514, 1278, 480],
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[194, 354, 810, 502, 388, 308, 536, 0, 342, 388, 730, 468, 354, 320, 662, 742, 856],
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[308, 696, 468, 844, 730, 194, 194, 342, 0, 274, 388, 810, 696, 662, 320, 1084, 514],
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[194, 742, 742, 890, 776, 240, 468, 388, 274, 0, 342, 536, 422, 388, 274, 810, 468],
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[536, 1084, 400, 1232, 1118, 582, 354, 730, 388, 342, 0, 878, 764, 730, 388, 1152, 354],
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[502, 594, 1278, 514, 400, 776, 1004, 468, 810, 536, 878, 0, 114, 308, 650, 274, 844],
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[388, 480, 1164, 628, 514, 662, 890, 354, 696, 422, 764, 114, 0, 194, 536, 388, 730],
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[354, 674, 1130, 822, 708, 628, 856, 320, 662, 388, 730, 308, 194, 0, 342, 422, 536],
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[468, 1016, 788, 1164, 1050, 514, 514, 662, 320, 274, 388, 650, 536, 342, 0, 764, 194],
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[776, 868, 1552, 560, 674, 1050, 1278, 742, 1084, 810, 1152, 274, 388, 422, 764, 0, 798],
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[662, 1210, 754, 1358, 1244, 708, 480, 856, 514, 468, 354, 844, 730, 536, 194, 798, 0],
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# fmt: on
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]
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data["num_vehicles"] = 4
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data["depot"] = 0
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return data
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# [END data_model]
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# [START solution_callback_printer]
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def print_solution(
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routing_manager: pywrapcp.RoutingIndexManager, routing_model: pywrapcp.RoutingModel
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):
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"""Prints solution on console."""
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print("################")
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print(f"Solution objective: {routing_model.CostVar().Value()}")
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total_distance = 0
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for vehicle_id in range(routing_manager.GetNumberOfVehicles()):
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index = routing_model.Start(vehicle_id)
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if routing_model.IsEnd(routing_model.NextVar(index).Value()):
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continue
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plan_output = f"Route for vehicle {vehicle_id}:\n"
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route_distance = 0
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while not routing_model.IsEnd(index):
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plan_output += f" {routing_manager.IndexToNode(index)} ->"
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previous_index = index
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index = routing_model.NextVar(index).Value()
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route_distance += routing_model.GetArcCostForVehicle(
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previous_index, index, vehicle_id
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)
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plan_output += f" {routing_manager.IndexToNode(index)}\n"
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plan_output += f"Distance of the route: {route_distance}m\n"
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print(plan_output)
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total_distance += route_distance
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print(f"Total Distance of all routes: {total_distance}m")
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# [END solution_callback_printer]
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# [START solution_callback]
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class SolutionCallback:
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"""Create a solution callback."""
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def __init__(
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self,
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manager: pywrapcp.RoutingIndexManager,
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model: pywrapcp.RoutingModel,
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limit: int,
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):
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# We need a weak ref on the routing model to avoid a cycle.
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self._routing_manager_ref = weakref.ref(manager)
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self._routing_model_ref = weakref.ref(model)
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self._counter = 0
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self._counter_limit = limit
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self.objectives = []
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def __call__(self):
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objective = int(
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self._routing_model_ref().CostVar().Value()
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) # pytype: disable=attribute-error
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if not self.objectives or objective < self.objectives[-1]:
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self.objectives.append(objective)
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print_solution(self._routing_manager_ref(), self._routing_model_ref())
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self._counter += 1
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if self._counter > self._counter_limit:
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self._routing_model_ref().solver().FinishCurrentSearch()
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# [END solution_callback]
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def main():
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"""Entry point of the program."""
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# Instantiate the data problem.
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# [START data]
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data = create_data_model()
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# [END data]
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# Create the routing index manager.
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# [START index_manager]
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routing_manager = pywrapcp.RoutingIndexManager(
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len(data["distance_matrix"]), data["num_vehicles"], data["depot"]
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)
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# [END index_manager]
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# Create Routing Model.
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# [START routing_model]
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routing_model = pywrapcp.RoutingModel(routing_manager)
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# [END routing_model]
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# Create and register a transit callback.
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# [START transit_callback]
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def distance_callback(from_index, to_index):
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"""Returns the distance between the two nodes."""
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# Convert from routing variable Index to distance matrix NodeIndex.
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from_node = routing_manager.IndexToNode(from_index)
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to_node = routing_manager.IndexToNode(to_index)
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return data["distance_matrix"][from_node][to_node]
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transit_callback_index = routing_model.RegisterTransitCallback(distance_callback)
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# [END transit_callback]
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# Define cost of each arc.
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# [START arc_cost]
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routing_model.SetArcCostEvaluatorOfAllVehicles(transit_callback_index)
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# [END arc_cost]
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# Add Distance constraint.
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# [START distance_constraint]
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dimension_name = "Distance"
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routing_model.AddDimension(
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transit_callback_index,
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0, # no slack
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3000, # vehicle maximum travel distance
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True, # start cumul to zero
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dimension_name,
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)
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distance_dimension = routing_model.GetDimensionOrDie(dimension_name)
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distance_dimension.SetGlobalSpanCostCoefficient(100)
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# [END distance_constraint]
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# Attach a solution callback.
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# [START attach_callback]
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solution_callback = SolutionCallback(routing_manager, routing_model, 15)
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routing_model.AddAtSolutionCallback(solution_callback)
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# [END attach_callback]
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# Setting first solution heuristic.
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# [START parameters]
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search_parameters = pywrapcp.DefaultRoutingSearchParameters()
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search_parameters.first_solution_strategy = (
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routing_enums_pb2.FirstSolutionStrategy.PATH_CHEAPEST_ARC
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)
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search_parameters.local_search_metaheuristic = (
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routing_enums_pb2.LocalSearchMetaheuristic.GUIDED_LOCAL_SEARCH
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)
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search_parameters.time_limit.FromSeconds(5)
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# [END parameters]
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# Solve the problem.
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# [START solve]
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solution = routing_model.SolveWithParameters(search_parameters)
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# [END solve]
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# Print solution on console.
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# [START print_solution]
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if solution:
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print(f"Best objective: {solution_callback.objectives[-1]}")
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else:
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print("No solution found !")
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# [END print_solution]
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if __name__ == "__main__":
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main()
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# [END program]
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