Route planning with capacity

[Ravi]

Hi All, 

ORTools has an example of how to specify maximum load capacities of vehicles. How can I specify an additional constraint that also specifies the minimum load that a truck needs for it to accept a consignment? 

That is, the total consignment to a truck should *NOT* be less than the minimum that the truck needs to accept a delivery.

Any suggestions?

Thanks! 

[Vincent Furnon]

Hi,

For VRPs:

You could force the lower bound of the cumul of end nodes of non-empty vehicles to be greater than this minimum, but this would make the life of the solver really hard. The alternative would be to use RoutingDimension::SetCumulVarSoftLowerBound on vehicle end nodes (applying a soft cost to vehicles which have not reached the minimum load); note that there is no easy way to put this cost only on non-empty vehicles so the best approach is to offset fixed costs of all vehicles by a value equal to the soft cost of being empty, to make empty vehicles "attractive". 

For PDPs (also applies to VRPs):

You could do something similar, applying RoutingDimension::SetCumulVarSoftLowerBound only to non-start/end nodes; you'd need to make sure you existing penalty costs (to make nodes optional) are high enough to balance soft minimum costs. 

Vincent

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[dhiraj shanbhag]

How to put a lower bound on  the cumul of end nodes of non-empty vehicles.

not soft lower bound...Is there a way to put hard lower bound. 

Thanks,

[Vincent Furnon]

Just constrain the cumul variable of the end of a vehicle: set its lower bound directly or add a more elaborate constraint stating next(start)!=end -> cumul(end) > bound (look at the reified version of inequality constraints).

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[dhiraj shanbhag]

I have added this:

 weight_dimension.CumulVar(routing.End(int(veh.index))).SetRange(lower_bound ,max_weight)

but this doesn't seem to work.

Should I add something like you mentioned in routing..solver.

Thanks,

[Aravind Reddy]

Did we get any working solution here?

[Mizux Seiha]

Did you try this ?

```python

solver = routing.solver()

for vehicle_id in range(manager.GetNumberOfVehicles()):

  end_index = routing.End(vehicle_id)

  solver.Add(weight_dimension.CumulVar(end_index) >= lower_bound * routing.ActiveVehicleVar(vehicle_id))
```

ref for RoutingModel::ActiveVehicleVar(): https://github.com/google/or-tools/blob/b37d9c786b69128f3505f15beca09e89bf078a89/ortools/constraint_solver/routing.h#L1214-L1216

[tril...@gmail.com]

Hi Vincent  

I am a newbee with ortools. I am trying to set  minimum  load for every acitve vehicles.

Here is my code :

  for vehicle_id in range(data['num_vehicles']):

        index = routing.End(vehicle_id)

        min_capacity =int(data["product_d_capacity"][vehicle_id][0])

        capacity_dimension.SetCumulVarSoftLowerBound(vehicle_id, min_capacity, 100000)

        routing.SetVehicleUsedWhenEmpty(True, vehicle_id)

but  minimum constrant works not correct.

Another approach is: routing.solver().Add(product_d_dimension.CumulVar(routing.End(vehicle_id)) >= (min_capacity * routing.ActiveVehicleVar(vehicle_id))) but very slow and time out after 30p if I use more than 50 nodes.

Can you advise  or any example?

I appreciate your help.

[Laurent Perron]

Search the mailing list. It is asked very regularly. 

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