Optaplanner VRP remove customer from working solution

Question

Based on this example from cloud balancing problem, I'm trying to remove customer from a working solution as follows:

Location toBeRemovedLocation = customerToBeRemoved.getLocation();
Location lookUpWorkingObject = (Location) scoreDirector.lookUpWorkingObject(toBeRemovedLocation);
scoreDirector.beforeProblemFactRemoved(lookUpWorkingObject);
routingSolution.getLocationList().remove(lookUpWorkingObject);
scoreDirector.afterProblemFactRemoved(lookUpWorkingObject);

Customer workingCustomer=(Customer) scoreDirector.lookUpWorkingObject(customerToBeRemoved);

for (Customer customer : routingSolution.getCustomerList()) {
    nextCustomer=customer.getNextCustomer();
    if (nextCustomer==workingCustomer) {
        scoreDirector.beforeVariableChanged(customer, "nextCustomer");
        customer.setNextCustomer(null);
        scoreDirector.afterVariableChanged(customer, "nextCustomer");
    }
}

scoreDirector.beforeEntityRemoved(workingCustomer);
routingSolution.getCustomerList().remove(workingCustomer);
scoreDirector.afterEntityRemoved(workingCustomer);
scoreDirector.triggerVariableListeners();

I got this exception as a result:

java.lang.IllegalStateException: The entity (Customer--6361356485874019865) has a variable (previousStandstill) with value (Customer--9027426768799526425) which has a sourceVariableName variable (nextCustomer) with a value (null) which is not that entity.Verify the consistency of your input problem for that sourceVariableName variable

After that, I tried to also setPreviousStandstill to null:

scoreDirector.beforeVariableChanged(customer, "previousStandstill");
customer.setPreviousStandstill(null);
scoreDirector.afterVariableChanged(customer, "previousStandstill");

But, I received:

java.lang.IllegalStateException: The entity (Customer--6361368382933429785) has a variable (previousStandstill) with value (Customer--9027434800388369945) which has a sourceVariableName variable (nextCustomer) with a value (null) which is not that entity.Verify the consistency of your input problem for that sourceVariableName variable.

Need help, please.

Adelinaadelind

@Geofrey De Smet – Adelinaadelind

Answer 1

Customers in VRP are chained/linked, if you currently have a chain [Customer1, Customer2, Customer3]

- Customer1: nextCustomer = Customer2
- Customer2: nextCustomer = Customer2, prevStandstill = Customer1
- Customer3: prevStandstill = Customer2

and you're trying to remove Customer2 from it, you have to fix both previous and next elements:

- Customer1: nextCustomer = Customer3
- Customer2: nextCustomer = null, prevStandstill = null
- Customer3: prevStandStill = Customer1

Umbelliferous