How to add a servicing time constraint to a vehicle routing problem with time window constraints

Question

I'm building a tour planner. This tour planner will be given travel time matrix for the itinerary of all places, opening and closing times of all locations and the stay/processing time at each location. I am using Google's OR tools to solve the problem

I've been successful in adding the time window constraints, but am not able to add the stay/processing time constraint to the solver. The documentation on google OR tools shows how to solve a vehicle routing problem with time window constraints, but there is no mention of how i could add more constraints to the problem.

I've been following this tutorial till now. https://developers.google.com/optimization/routing/vrptw

The expected output for the planner should consider all the three time constraints mentioned above ie opening time, closing time and stay/processing time

Answer 1

This is actually really simple. Since the stay time/processing time will depend only on the destination node, this can be directly added to the time matrix that will be used to solve the problem. For a N*N time matrix where N is the number of nodes in the problem, and a 1*N matrix of stay time, the stay time matrix has to be added to each row of the time matrix to get a matrix that includes both the time matrix and the stay time matrix. Leaving this here for anyone who may face the same problem.

Answer 2

Your transit callback should return the sum of the service time and the travel time. ie transit(i, j) == service_time(i) + travel_time(i, j)

If your service time depends on the vehicle you can register a transit callback per vehicle type then use the AddDimension() overload which take a transit callback index array.