JSprit not using closer vehicle, due to time issues

Question

Single-job schedule with two vehicles. One vehicle starts close to the job, the other starts far from the job. Seems it should prefer to use the closer vehicle, as there's a cost-per-distance. But it uses the farther one, if there's a non-zero setCostPerWaitingTime(). Why?

public void testUseCloserVehicleWhenCostsAreSet() throws Exception {
    VehicleType type = VehicleTypeImpl.Builder.newInstance("generic")
            .setCostPerDistance(0.017753)
            //.setCostPerTransportTime(1.0)
            .setCostPerWaitingTime(1.0)
            .build();
    double serviceTime = 420.0;
    Location pointA = Location.newInstance(100.0, 100.0);
    Location pointB = Location.newInstance(100.0, 200.0);
    Location closeToPointA = Location.newInstance(110.0, 110.0);
    Location farFromPointA = Location.newInstance(500.0, 110.0);
    VehicleRoutingProblem vrp = VehicleRoutingProblem.Builder
            .newInstance()
            .setFleetSize(VehicleRoutingProblem.FleetSize.FINITE)
            .addVehicle(VehicleImpl.Builder.newInstance("CloseBy")
                    .setType(type)
                    .setStartLocation(closeToPointA)
                    .build())
            .addVehicle(VehicleImpl.Builder.newInstance("FarAway")
                    .setType(type)
                    .setStartLocation(farFromPointA)
                    .build())
            .addJob(Shipment.Builder.newInstance("123")
                    .setPickupLocation(pointA)
                    .setPickupServiceTime(serviceTime)
                    .setDeliveryLocation(pointB)
                    .setDeliveryServiceTime(serviceTime)
                    .setPickupTimeWindow(new TimeWindow(36000.0, 36360.0))
                    .setDeliveryTimeWindow(new TimeWindow(36360.0, 36720.0))
                    .setMaxTimeInVehicle(720.0)
                    .build())
            .build();

    VehicleRoutingAlgorithm algorithm = Jsprit.Builder.newInstance(vrp)
            .buildAlgorithm();

    VehicleRoutingProblemSolution bestSolution = Solutions.bestOf(algorithm.searchSolutions());
    SolutionPrinterWithTimes.print(vrp, bestSolution, SolutionPrinterWithTimes.Print.VERBOSE);
    System.out.flush();
    assertEquals("CloseBy", bestSolution.getRoutes().iterator().next().getVehicle().getId());
}

Result:

+----------------------------------------------------------+
| solution                                                 |
+---------------+------------------------------------------+
| indicator     | value                                    |
+---------------+------------------------------------------+
| costs         | 35616.03246830352                        | 
| noVehicles    | 1                                        | 
| unassgndJobs  | 0                                        | 
+----------------------------------------------------------+
+--------------------------------------------------------------------------------------------------------------------------------+
| detailed solution                                                                                                              |
+---------+----------------------+-----------------------+-----------------+-----------------+-----------------+-----------------+
| route   | vehicle              | activity              | job             | arrTime         | endTime         | costs           |
+---------+----------------------+-----------------------+-----------------+-----------------+-----------------+-----------------+
| 1       | FarAway              | start                 | -               | undef           | 0               | 0               |
| 1       | FarAway              | pickupShipment        | 123             | 400             | 36420           | 35607           |
| 1       | FarAway              | deliverShipment       | 123             | 36520           | 36940           | 35609           |
| 1       | FarAway              | end                   | -               | 37350           | undef           | 35616           |
+--------------------------------------------------------------------------------------------------------------------------------+
junit.framework.ComparisonFailure: 
Expected :CloseBy
Actual   :FarAway

I suspect it has something to do with the vehicle arriving at 400 for a job that can't start until 36000. Is there a way to prevent that, so the vehicle starts only as early as needed to reach the first job? Does setCostPerWaitingTime do something other than what I think?

JSprit not using closer vehicle, due to time issues

Answers (1)

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