vrp_breaks.py

#!/usr/bin/env python3
# Copyright 2010-2024 Google LLC
# 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.

# [START program]
"""Vehicle Routing Problem (VRP) with breaks.

   This is a sample using the routing library python wrapper to solve a VRP
   problem.
   A description of the problem can be found here:
   http://en.wikipedia.org/wiki/Vehicle_routing_problem.

   Durations are in minutes.
"""

# [START import]
from ortools.constraint_solver import routing_enums_pb2
from ortools.constraint_solver import pywrapcp
# [END import]


# [START data_model]
def create_data_model():
    """Stores the data for the problem."""
    data = {}
    data["num_vehicles"] = 4
    data["depot"] = 0
    data["time_matrix"] = [
        [0, 27, 38, 34, 29, 13, 25, 9, 15, 9, 26, 25, 19, 17, 23, 38, 33],
        [27, 0, 34, 15, 9, 25, 36, 17, 34, 37, 54, 29, 24, 33, 50, 43, 60],
        [38, 34, 0, 49, 43, 25, 13, 40, 23, 37, 20, 63, 58, 56, 39, 77, 37],
        [34, 15, 49, 0, 5, 32, 43, 25, 42, 44, 61, 25, 31, 41, 58, 28, 67],
        [29, 9, 43, 5, 0, 26, 38, 19, 36, 38, 55, 20, 25, 35, 52, 33, 62],
        [13, 25, 25, 32, 26, 0, 11, 15, 9, 12, 29, 38, 33, 31, 25, 52, 35],
        [25, 36, 13, 43, 38, 11, 0, 26, 9, 23, 17, 50, 44, 42, 25, 63, 24],
        [9, 17, 40, 25, 19, 15, 26, 0, 17, 19, 36, 23, 17, 16, 33, 37, 42],
        [15, 34, 23, 42, 36, 9, 9, 17, 0, 13, 19, 40, 34, 33, 16, 54, 25],
        [9, 37, 37, 44, 38, 12, 23, 19, 13, 0, 17, 26, 21, 19, 13, 40, 23],
        [26, 54, 20, 61, 55, 29, 17, 36, 19, 17, 0, 43, 38, 36, 19, 57, 17],
        [25, 29, 63, 25, 20, 38, 50, 23, 40, 26, 43, 0, 5, 15, 32, 13, 42],
        [19, 24, 58, 31, 25, 33, 44, 17, 34, 21, 38, 5, 0, 9, 26, 19, 36],
        [17, 33, 56, 41, 35, 31, 42, 16, 33, 19, 36, 15, 9, 0, 17, 21, 26],
        [23, 50, 39, 58, 52, 25, 25, 33, 16, 13, 19, 32, 26, 17, 0, 38, 9],
        [38, 43, 77, 28, 33, 52, 63, 37, 54, 40, 57, 13, 19, 21, 38, 0, 39],
        [33, 60, 37, 67, 62, 35, 24, 42, 25, 23, 17, 42, 36, 26, 9, 39, 0],
    ]
    # 15 min of service time
    data["service_time"] = [15] * len(data["time_matrix"])
    data["service_time"][data["depot"]] = 0
    assert len(data["time_matrix"]) == len(data["service_time"])
    return data
    # [END data_model]


# [START solution_printer]
def print_solution(manager, routing, solution):
    """Prints solution on console."""
    print(f"Objective: {solution.ObjectiveValue()}")

    print("Breaks:")
    intervals = solution.IntervalVarContainer()
    for i in range(intervals.Size()):
        brk = intervals.Element(i)
        if brk.PerformedValue():
            print(
                f"{brk.Var().Name()}: "
                + f"Start({brk.StartValue()}) Duration({brk.DurationValue()})"
            )
        else:
            print(f"{brk.Var().Name()}: Unperformed")

    time_dimension = routing.GetDimensionOrDie("Time")
    total_time = 0
    for vehicle_id in range(manager.GetNumberOfVehicles()):
        index = routing.Start(vehicle_id)
        plan_output = f"Route for vehicle {vehicle_id}:\n"
        while not routing.IsEnd(index):
            time_var = time_dimension.CumulVar(index)
            plan_output += f"{manager.IndexToNode(index)} "
            plan_output += f"Time({solution.Value(time_var)}) -> "
            index = solution.Value(routing.NextVar(index))
        time_var = time_dimension.CumulVar(index)
        plan_output += f"{manager.IndexToNode(index)} "
        plan_output += f"Time({solution.Value(time_var)})\n"
        plan_output += f"Time of the route: {solution.Value(time_var)}min\n"
        print(plan_output)
        total_time += solution.Value(time_var)
    print(f"Total time of all routes: {total_time}min")
    # [END solution_printer]


def main():
    """Solve the VRP with time windows."""
    # Instantiate the data problem.
    # [START data]
    data = create_data_model()
    # [END data]

    # Create the routing index manager.
    # [START index_manager]
    manager = pywrapcp.RoutingIndexManager(
        len(data["time_matrix"]), data["num_vehicles"], data["depot"]
    )
    # [END index_manager]

    # Create Routing Model.
    # [START routing_model]
    routing = pywrapcp.RoutingModel(manager)
    # [END routing_model]

    # Create and register a transit callback.
    # [START transit_callback]
    def time_callback(from_index, to_index):
        """Returns the travel time + service time between the two nodes."""
        # Convert from routing variable Index to time matrix NodeIndex.
        from_node = manager.IndexToNode(from_index)
        to_node = manager.IndexToNode(to_index)
        return data["time_matrix"][from_node][to_node] + data["service_time"][from_node]

    transit_callback_index = routing.RegisterTransitCallback(time_callback)
    # [END transit_callback]

    # Define cost of each arc.
    # [START arc_cost]
    routing.SetArcCostEvaluatorOfAllVehicles(transit_callback_index)
    # [END arc_cost]

    # Add Time Windows constraint.
    time = "Time"
    routing.AddDimension(
        transit_callback_index,
        10,  # needed optional waiting time to place break
        180,  # maximum time per vehicle
        True,  # Force start cumul to zero.
        time,
    )
    time_dimension = routing.GetDimensionOrDie(time)
    time_dimension.SetGlobalSpanCostCoefficient(10)

    # Breaks
    # [START break_constraint]
    # warning: Need a pre-travel array using the solver's index order.
    node_visit_transit = [0] * routing.Size()
    for index in range(routing.Size()):
        node = manager.IndexToNode(index)
        node_visit_transit[index] = data["service_time"][node]

    break_intervals = {}
    for v in range(manager.GetNumberOfVehicles()):
        break_intervals[v] = [
            routing.solver().FixedDurationIntervalVar(
                50,  # start min
                60,  # start max
                10,  # duration: 10 min
                False,  # optional: no
                f"Break for vehicle {v}",
            )
        ]
        time_dimension.SetBreakIntervalsOfVehicle(
            break_intervals[v], v, node_visit_transit  # breaks  # vehicle index
        )
    # [END break_constraint]

    # Setting first solution heuristic.
    # [START parameters]
    search_parameters = pywrapcp.DefaultRoutingSearchParameters()
    search_parameters.first_solution_strategy = (
        routing_enums_pb2.FirstSolutionStrategy.PATH_CHEAPEST_ARC
    )
    search_parameters.local_search_metaheuristic = (
        routing_enums_pb2.LocalSearchMetaheuristic.GUIDED_LOCAL_SEARCH
    )
    # search_parameters.log_search = True
    search_parameters.time_limit.FromSeconds(2)
    # [END parameters]

    # Solve the problem.
    # [START solve]
    solution = routing.SolveWithParameters(search_parameters)
    # [END solve]

    # Print solution on console.
    # [START print_solution]
    if solution:
        print_solution(manager, routing, solution)
    else:
        print("No solution found !")
    # [END print_solution]


if __name__ == "__main__":
    main()
# [END program]