Extending the optaplanner vrp example to tackle multi trip

[Gustavo Arzola]

Hello

First of all I want to thank the optaplanner team for all the great work. It is really an amazing piece of software and I am very exited to see the community is growing and every release come with great improvements.

At my company we are currently using optaplanner to solve a vehicle routing problem with great results, we built a web app to manage vehicles, clientes, locations, depots and to show a graphic representation of the solution (including showing the locations in a map). We wrapped the solver in a spring java app with a rest interface to receive request and solve the problem. We are using Google maps to get distance-time data. Now we need to implement multirip....

To tackle the multitrip part I am following this approach:

1.- I added readyTime, endOfTrip and dueTime members to Vehicle class

2.- I created a rule to prevent arrivals at customers after vehicle->dueTime

3.- I modified the ArrivalTimeUpdateListener to consider the vehicle->readyTime when calculating the departureTime from a vehicle (using Math.max(depot-

>readyTime, vehicle->readyTime)

4.- At this point I started using the vehicle class as if it were a vehicle trip instead of a vehicle (I still don´t change the name but that is the idea )

5.- I created a member nextVehicle in vehicle to represent the next trip

6.- For testing purposes I manually link two vehicles (or vehicle trips) before sending it to solver->solve

7.- In the ArrivalTimeUpdatingVariableListener class I extended the method that updates the arrival times to consider updating the nextVehicle->readyTime and by consequence the arrival times of the customers that belong to the next trip (and so on when there are more than two trips)

I am sure this is not the most elegant solution, but I tried other approaches (using custom shadow variable on Vehicle for instance) but it couldn´t make it work.

The problem I am facing right now is that I don´t get to understand the state of the model when ArrivalTimeUpdatingVariableListener is called, maybe someone faced similar problem and can help me. What i found  (after try and error) is:

- the customer.getVehice() method not always returns a value (distinct from null value), it seems to get updated some time after the previousStandstill change triggers the listener "updateArrivalTime" method. 

     - In construction fase when a customer get assign to a vehicle the customer.getVehice()  method returns null (it came from "not assigned")

     - In construction fase when a customer "is freed" the customer.getVehice() method returns the "previous vehicle"

     - In local search fase when a customer get assign to a vehicle the customer.getVehice() method returns the "previous vehicle" (original vehicle)

     - In local search fase when a customer go back to the original vehicle the customer.getVehice() method returns the "previous assign vehicle"

Any thoughts on this? Am I making right assumptions? (because originally I considered customer.getVehicle() as the "actual" vehicle and the solutions were completely wrong...)

- The order of triggering the previousStandstill change it´s kind of difficult to understand (for me). I mean when moving customers or swapping them between vehicles...any thoughts or hints on were to find info? 

- Can I access some variables from the "previous state of the model" when the solver makes a move?, because I am thinking I will need that if I continue with this approach (to update the vehicle->endOfTrip that is the nextVehicle->readyTime when the customer is the last one on the chain for instance)

and finally...am i doing something completely wrong conceptually ?

Any comments will be greatly appreciated  (and sorry my grammar, I am native spanish speaker)

[Geoffrey De Smet]

Thanks for the kind words about OptaPlanner :)

Did we talk on freenode irc on #optaplanner the other day?  Is this the case of the shadow vars not being refreshed because a problem fact change changed a problem property that also affects a shadow var?

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With kind regards / Met vriendelijke groeten,
Geoffrey De Smet

[Geoffrey De Smet]

Duplicated here:
http://stackoverflow.com/questions/35184608/optaplanner-extending-the-vrp-example-to-tackle-multi-trip-case

Looks like PLANNER-252, fixed in optaplanner 6.3.0. See release notes.

With kind regards,
Geoffrey De Smet