Switchable Pickups and Deliveries

[ZhenxiangICD]

Hello,

I'm new to the OR tool and I'm trying to model a problem where pickup and delivery nodes can be switched. Meaning a vehicle can either travel from A to B or from B to A, but it can only choose one.

I tried to implement the following code but didn't find it successful.

var totalPath = (costMatrix.GetLength(0)-1) / (int)2; //assume all nodes expect node 0 are either pickup or deliveries location
var PickDeliveries = new int[2 * totalPath][];
var vehicle_num = 2
var depot = 0

for (int i = 0; i < totalPath; i++)
{
    int a = 1 + i * 2;
    int b = 2 + i * 2 ;
    PickDeliveries[2 * i] = new int[] { a, b };
    PickDeliveries[2 * i + 1] = new int[] { b, a };
}

var manager = new RoutingIndexManager(CostMatrix.GetLength(0), vehicle_num, depot);
var routing = new RoutingModel(manager);

int transitCallbackIndex = Routing.RegisterTransitCallback((long fromIndex, long toIndex) =>
{
    var fromNode = manager.IndexToNode(fromIndex);
    var toNode = manager.IndexToNode(toIndex);
    return costMatrix[fromNode, toNode];
});

routing.SetArcCostEvaluatorOfAllVehicles(transitCallbackIndex);
routing.AddDimension(transitCallbackIndex, 0, 30000, true, "Distance");
routingDimension distanceDimension = Routing.GetMutableDimension("Distance");
distanceDimension.SetGlobalSpanCostCoefficient(100);

solver = Routing.solver();

for (int i = 0; i < this.PickDeliveries.GetLength(0); i++)
{
    long pickupIndex = manager.NodeToIndex(PickDeliveries[i][0]);
    long deliveryIndex = manager.NodeToIndex(PickDeliveries[i][1]);
    Routing.AddPickupAndDelivery(pickupIndex, deliveryIndex);
    solver.Add(solver.MakeEquality(Routing.VehicleVar(pickupIndex), Routing.VehicleVar(deliveryIndex)));
    solver.Add(solver.MakeLessOrEqual(distanceDimension.CumulVar(pickupIndex),
        distanceDimension.CumulVar(deliveryIndex)));
}

for (int i = 0; i < totalPath; i++)
{
    int a =  i * 2 + 1;
    int b =  i * 2 + 2;
    Routing.AddDisjunction(new long[] { a, b }, 100000, 1);
}

I think I have some misunderstandings on how disjunction works. Any suggestions?