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simple_routing_program

<table align="left"> <td> <a href="https://colab.research.google.com/github/google/or-tools/blob/main/examples/notebook/constraint_solver/simple_routing_program.ipynb">Run in Google Colab</a> </td> <td> <a href="https://github.com/google/or-tools/blob/main/ortools/constraint_solver/samples/simple_routing_program.py">View source on GitHub</a> </td> </table>

First, you must install ortools package in this colab.

python

%pip install ortools

Vehicle Routing example.

python

from ortools.constraint_solver import routing_enums_pb2
from ortools.constraint_solver import pywrapcp



def main():
    """Entry point of the program."""
    # Instantiate the data problem.
    num_locations = 5
    num_vehicles = 1
    depot = 0

    # Create the routing index manager.
    manager = pywrapcp.RoutingIndexManager(num_locations, num_vehicles, depot)

    # Create Routing Model.
    routing = pywrapcp.RoutingModel(manager)

    # Create and register a transit callback.
    def distance_callback(from_index, to_index):
        """Returns the absolute difference between the two nodes."""
        # Convert from routing variable Index to user NodeIndex.
        from_node = int(manager.IndexToNode(from_index))
        to_node = int(manager.IndexToNode(to_index))
        return abs(to_node - from_node)

    transit_callback_index = routing.RegisterTransitCallback(distance_callback)

    # Define cost of each arc.
    routing.SetArcCostEvaluatorOfAllVehicles(transit_callback_index)

    # Setting first solution heuristic.
    search_parameters = pywrapcp.DefaultRoutingSearchParameters()
    search_parameters.first_solution_strategy = (
        routing_enums_pb2.FirstSolutionStrategy.PATH_CHEAPEST_ARC
    )  # pylint: disable=no-member

    # Solve the problem.
    assignment = routing.SolveWithParameters(search_parameters)

    # Print solution on console.
    print(f"Objective: {assignment.ObjectiveValue()}")
    index = routing.Start(0)
    plan_output = "Route for vehicle 0:\n"
    route_distance = 0
    while not routing.IsEnd(index):
        plan_output += f"{manager.IndexToNode(index)} -> "
        previous_index = index
        index = assignment.Value(routing.NextVar(index))
        route_distance += routing.GetArcCostForVehicle(previous_index, index, 0)
    plan_output += f"{manager.IndexToNode(index)}\n"
    plan_output += f"Distance of the route: {route_distance}m\n"
    print(plan_output)


main()