使用 OptaPlanner 解决带时间窗的车辆路线问题

Question

Hello OptaPlanner community. I am developing a Rest API to plan the routes of a fleet of vehicles. Looking for a tool that would help me I found Optaplanner, and I have seen that it has several success stories. In a first stage I made a planning taking into account the fastest distance and the capacity of the vehicle to cover all its visits. And I got the results I expected. Now I'm planning for time windows of visits and deposits, but I'm not successful yet.

Requirements

R1- I have a fleet of vehicles. Each vehicle has a capacity and its deposit and this deposit has a window of time. From the example of OptaPlanner for VRP I have only made a variation on the capacity that I handle as a float. As I understand it, all the vehicles in the OptaPlanner example are moved for a single depot. In my case, each vehicle has its own depot, each vehicle has its own fixed depot, and it is possible that several vehicles have the same depot.

R2- I have the visits (delivery services). Each visit has a demand and a window of time. From the example of OptaPlanner for VRP I have only made one modification regarding the demand that I handle it as a type "float".

In this process of adding this variant with TW to my routing problem I have some doubts and problems since I have not obtained a viable solution to my problem by applying TW:

1- I understand that I do not need to make modifications to the OptaPlanner example so that each vehicle cannot transport more items than its capacity. I only need to adjust the constrint provider so that the calculation is on float. I would like to know if I am right ? and on the other hand How I can manage the capacities and demands with dimensions?, in OptaPlanner it is a number but I need to manage it as volume and weight.

In the OptaPlanner domain I modified the variables "capacity" from vehicle and "demand" from visit, both to type "float".

Constraint vehicleCapacity(ConstraintFactory constraintFactory) {
    return constraintFactory.from(PlanningVisit.class)
            .groupBy(PlanningVisit::getVehicle, sumBigDecimal(PlanningVisit::getDemand))
            .filter((vehicle, demand) -> demand.compareTo(vehicle.getCapacity()) > 0)
            .penalizeLong(
                    "vehicle capacity",
                    HardSoftLongScore.ONE_HARD,
                    (vehicle, demand) -> demand.subtract(vehicle.getCapacity()).longValue());
}

2- In the OptaPlanner example I understand that the TW is a long that multiplies by a thousand, but I do not know if this long expresses an hour or date, or if it is just the hour converted into minutes and multiplied by a thousand. What I am doing is converting the TW to minutes and multiplied by a thousand, for example if it is 8am, the ready time is a log equal to '480000'. In the case of the service duration, I do not multiply it by 1000, I always treat it as 10 minutes. Am I doing the conversion correctly? , is this the long that OptaPlanner expects?

3- I understand that using the example of OptaPlanner for time windows I can solve this requirement (R2), without making variations, however for some reason that I can not find is not giving me back a feasible solution. It returns me for example: time spent (5000), best score (-3313987hard/-4156887soft).

I have thought that the error could be in the conversion of the dates of the time window or maybe some hard constraint that I lack, because the arrival times of the visits do not adapt to the time windows defined for visits nor for deposits.

For example: I have 4 visits with time windows, 2 in the morning (visit 2 and visit 4) and 2 in the afternoon (visit 1 and visit 3). I have two vehicles, vehicle 1 leaves a depot 1 that has a time window in a morning schedule and the other vehicle leaves a depot 2 that has a time window in an afternoon schedule. So I expect vehicle 1 to conduct the visits that have a time window in the morning and vehicle 2 to conduct the visits that have a time window in the afternoon: [vehicle 1: {visit 2, visit 4}, vehicle 2: {visit 1, visit 3}]

I must be doing something very wrong, but I can't find where, not only does it not meet the TW of the deposit, but the arrival times of each visit exceed the defined TW. I don't understand why I get such big arrival times, that even exceed the defined limit for 1 day (all arrival times are over 1440000 = 1400min = 24 = 12am), that is, they arrived after this time.

This is the result I have obtained: score (-3313987hard/-4156887soft)

Route 1 referring to the route followed by vehicle 1 Vehicle 1

Depot 1 with TW (8:00 a 13:00)
    ready_time: 480000
    due_time: 780000


Visit 2 (8:30 a 12:30)
    ready_time: 510000
    due_time: 750000
    service_duraration 10 = 10

    arrival_time: 1823943
    departure_time: 1833943

Visit 4 (9:30 a 12:30)
    ready_time: 570000
    due_time: 750000
    service_duraration 10

    arrival_time: 1739284
    departure_time: 1739294

Visit 3 (14:40 a 15:30)
    ready_time: 880000
    due_time: 930000
    service_duraration 10

    arrival_time: 1150398
    departure_time: 1150408

Route 2 referring to the route followed by vehicle 2 Vehicle 2

Depot 2 with TW (12:00 a 17:00)
    ready_time: 720000
    due_time: 1020000

Visit 1 (14:00 a 16:30)
    ready_time: 840000
    due_time: 990000
    service_duraration 10 = 10

    arrival_time: 2523243
    departure_time: 2523253

This is my code, it can give you a better context. This is my VariableListerner for updating the shadow variable 'arrival time'. I have not made any modifications, however the arrival times returned to me for each visit do not comply with the TW.

public class ArrivalTimeUpdatingVariableListener implements VariableListener<PlanningVisit> {
    ...

    protected void updateArrivalTime(ScoreDirector scoreDirector, TimeWindowedVisit sourceCustomer) {

       Standstill previousStandstill = sourceCustomer.getPreviousStandstill();
       Long departureTime = previousStandstill == null ? null
               : (previousStandstill instanceof TimeWindowedVisit)
               ? ((TimeWindowedVisit) previousStandstill).getDepartureTime()
               : ((TimeWindowedDepot) ((PlanningVehicle) 
                                 previousStandstill).getDepot()).getReadyTime();
       TimeWindowedVisit shadowCustomer = sourceCustomer;
       Long arrivalTime = calculateArrivalTime(shadowCustomer, departureTime);
       while (shadowCustomer != null && !Objects.equals(shadowCustomer.getArrivalTime(), 
           arrivalTime)) {
               scoreDirector.beforeVariableChanged(shadowCustomer, "arrivalTime");
               shadowCustomer.setArrivalTime(arrivalTime);
               scoreDirector.afterVariableChanged(shadowCustomer, "arrivalTime");
               departureTime = shadowCustomer.getDepartureTime();
               shadowCustomer = shadowCustomer.getNextVisit();
               arrivalTime = calculateArrivalTime(shadowCustomer, departureTime);
             }        
        }

    private Long calculateArrivalTime(TimeWindowedVisit customer, Long previousDepartureTime) {
       if (customer == null || customer.getPreviousStandstill() == null) {
              return null;
       }
       if (customer.getPreviousStandstill() instanceof PlanningVehicle) {
           // PreviousStandstill is the Vehicle, so we leave from the Depot at the best suitable time
           return Math.max(customer.getReadyTime(),
                     previousDepartureTime + customer.distanceFromPreviousStandstill());
       }
       return previousDepartureTime + customer.distanceFromPreviousStandstill();
     }
}

And this service is where I build the domain entities from the data stored in the database (find). This TimeWindowedVehicleRoutingSolution is the one I use in the solver.

   public TimeWindowedVehicleRoutingSolution find(UUID jobId) {
        //load VRP from DB
        RoutingProblem byJobId = routingProblemRepository.findVRP(jobId);
        Set<Vehicle> vehicles = byJobId.getVehicles();
        Set<Visit> visits = byJobId.getVisits();

        //building solution
        List<PlanningDepot> planningDepots = new ArrayList<>();
        List<PlanningVehicle> planningVehicles = new ArrayList<>();
        List<PlanningVisit> planningVisits = new ArrayList<>();


        vehicles.forEach(vehicle -> {
            //submit to planner location of the deposit, add to matrix for calculating distance
            PlanningLocation planningLocation = 
                        optimizer.submitToPlanner(vehicle.getDepot().getLocation());

            //Depot, Vehicle and Visit are my persistence JPA entities, they are not the OptaPlanner 
             domain entities.
            //The OptaPlanner domain entities are: PlanningVehicle, PlanningDepot and PlanningVisit
            //I build the entities of the optaplanner domain from my persistence entities

            Depot depot = vehicle.getDepot();
            TimeWindowedDepot timeWindowedDepot = new TimeWindowedDepot();
            TimeWindowedDepot timeWindowedDepot = new TimeWindowedDepot(depot.getId(), 
                     planningLocation, depot.getStart(), depot.getEnd());

        PlanningVehicle planningVehicle = new PlanningVehicle();
        planningVehicle.setId(vehicle.getId());
        planningVehicle.setCapacity(vehicle.getCapacity());
        // each vehicle has its deposit
        planningVehicle.setDepot(timeWindowedDepot);

        planningVehicles.add(planningVehicle);
       });

       visits.forEach(visit -> {
           //submit to planner location of the visit, add to matrix for calculating distance
            PlanningLocation planningLocation = optimizer.submitToPlanner(visit.getLocation());

            TimeWindowedVisit timeWindowedVisit = new TimeWindowedVisit();
            TimeWindowedVisit timeWindowedVisit = new TimeWindowedVisit(visit.getId(),     
                  planningLocation, visit.getLoad(),visit.getStart(), visit.getEnd(), 
                  visit.getServiceDuration());

            planningVisits.add(timeWindowedVisit);
      });

    //create TWVRP
    TimeWindowedVehicleRoutingSolution solution = new TimeWindowedVehicleRoutingSolution();
    solution.setId(jobId);
    solution.setDepotList(planningDepots);
    solution.setVisitList(planningVisits);
    solution.setVehicleList(planningVehicles);

    return solution;
}

Then I create the solver, start the optimization and finally save the best:

public void solve(UUID jobId) {
    if (!planRepository.isResolved(jobId)) {
        logger.info("Starting solver");

        TimeWindowedVehicleRoutingSolution solution = null;
        TimeWindowedVehicleRoutingSolution timeWindowedVehicleRoutingSolution = find(jobId);
        
        try {
            SolverJob<TimeWindowedVehicleRoutingSolution, UUID> solverJob = 
                           solverManager.solve(jobId, timeWindowedVehicleRoutingSolution);

            solution = solverJob.getFinalBestSolution();
            save(jobId, solution);

        } catch (InterruptedException | ExecutionException e) {
            e.printStackTrace();
        }
    } else
        logger.info("This job already has a solution");
}

Any help on where the error is will be welcome. I am starting with Optaplanner, please any comments will be very helpful. Thank you very much!

Sorry about the calligraphy, English is not my language.

Answer 1

Thank you very much Geoffrey, I applied your suggestions and found the source of my problem. Grateful for your help!

I will comment on what happened, in case it is useful to someone: It happens that I was using for the calculation of the distance the example of OptaWeb, that uses GrahHopper for this end and by default it returns the minimum distance, reason why calculation is as far as time. And by introducing time windows, I was breaking the score in:

Math.max(customer.getReadyTime(),
previousDepartureTime + customer.distanceFromPreviousStandstill())

My score was broken because I did not use the same conversion for all variables, the TW: ready time and departure time was expressed in minutes and multiplied by a thousand, while the distance was in milliseconds.

Example:

• ready_time: 480000 (8:00 * 60 * 1000)
• due_time: 780000 (13:00 * 60 * 1000)

As the distance returned to me:

• distance: 641263

And therefore my score was broken.

What I did was to convert all my time variables to milliseconds:

"HH:MM", HH * 3 600 000 and MM * 60 000

Example:

• ready_time: 28 800 000
• due_time: 46 800 000
• service_duration: 60 000 (10min per visit)

Now ready! The arrival time of each vehicle to your visits is adjusted to the defined time windows.