VRP With Priority Stops (orders)

RustyRex

Is there any way to flag specific orders so that are always reached in a route?  I tried using the time constraints and that seems to help some, but there are still scenarios where my priorities orders (ones that now have a time window) are  not reached.  What i am saying is, can I tell it, given these orders that must be fulfilled, give me the best routes to service these orders and any other 'normal' orders that can be reached.   I know i can lock a sequence, but then i have to lock at route too.  I want the give the solver that flexibility. 

HeatherMoe

Hello

There are two main options right now for marking something as required.  The first one you seem to know about but for completeness I'll explain incase someone else is having the same question.  Solve the problem in two steps, the first time mark all of the required stops with an assignment rule of "Override" and all of the optional ones as "Exclude."  This will put all of the required routes onto a route if it is at all possible and just ignore the additional ones.  For the second step mark all of the required orders with an assignment rule of either "Preserve Route and Relative Sequence" or "Preserve Route" and mark all of the optional orders with an assignment rule of "Override."  This tells the solver that the required stops have to stay on the route they are currently on either allowing for re-sequencing or not depending on which assignment rule you choose and then adds in as many optional orders as possible.  They can be inserted into the routes that already have required orders.  Depending on the location of the required orders this can sometimes give routes that crisscross because of the solver keeping the orders on specific routes.  The benefit of this method though is it makes sure all of the required stops are routed

The other option is to use the revenue field for the orders.  This is a harder story to line out with specifics because it really depends on the other costs that are in your problem.  But in general give the required orders a really large revenue and the optional ones a revenue of zero.  Run it and see how it does.  If it still isn't getting all of the required stops try increasing the revenue and rerunning.  This method does a better job with the routing optimization portion as it doesn't lock orders on a sub-optimal route but it does not guarantee that required orders are routed (usually with the right revenues it does pretty well through).  The reported costs for the routes are also now artificially changed because of the fake revenue values.

Hope this helps,

Heather