Prevent vehicle to visit depo during trip

[Burhan]

Requirement overview:

Trip route can have following type of task

• Delivery only

• Pickup only

• Pickup from one location and deliver to another location

Condition: Once a trip starts from depo, it should come back only when the trip is completed. During the trip it shouldn’t come to depo. 

As we understand, OR tools need delivery and pickup location for each order else it's giving issues.

Ref: https://groups.google.com/g/or-tools-discuss/c/WyEOZAv8IJs/m/PxWb7Lq7AwAJ 

To overcome this, for all delivery orders we add depo as pick location and for all pick orders, we add depo as delivery location. This is working fine if all orders are for delivery. However if orders are having a mix of delivery and pick, in this scenario, during the trip if depo location is near to the last pick node, vehicle will go to depot if OR-tools is optimizing route based on location (considering last pick needs to be delivered at depo). 

This leads to wrong route optimisation. Looking for help here. Also pls. advice if we are missing something or having wrong understanding. 

[Laurent Perron]

is this a duplicate of the previous question on the same topic ?

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[Burhan]

Yes

Since last one was having brief details, added more details. 

[Burhan]

Wondering if you meant the question on stackexchange & this... If so, yes. 

[blind.line]

For this kind of thing, I usually use a conditional constraint. 

The condition is that the NextVar of the All(not-depot nodes) is the depot. 

The constraint then is that the dimension in question is empty. 

In words, if the vehicle is heading to the depot to pick up more stuff, then it cannot do so unless it is empty. 

You can play games with multiple dimensions to fine tune that. Say dimension A is for things loaded at depot, and B for things loaded in the field. Then even if B pickups are made, you can’t drop them at depot until all A items are delivered and vehicle is empty. 

These conditional constraints do slow the solver down a little bit. 

James

On Jan 9, 2022, at 03:34, Burhan <bur...@connectsys.in> wrote:



[Anuj Gupta]

I didn't get in completely, can you please explain it a little bit more?