Originally posted by: reru90

Hi everyone,

I need urgent help from you, please.  
I impementize VRP model. Although I have done the constr and objective (minimize distance+waiting+delay) correctly, but the correct Startservicetimes at the nodes cannot generate. Startservicetime entered as dvar. I share here the constraints associated with start service time.  here is x[k][i][j] binary. 

forall (k in Machine, i in OrdersandDepots) 

        (Startservicetime[k][j] >= Distance[i][j] + waitingtime[k][j] + delay[k][j] + Startservicetime[k][i] - bigM*(1 - x[k][i][j]));

forall(i, j in 
OrdersandDepots, k in 
Machine)
        waitingtime[k][j] >= earliestStime[j]* x[k][i][j] - Startservicetime[k][j];  
        
forall(j in 
OrdersandDepots, k in 
Machine)              
 delay[k][j] >= Startservicetime[k][j] - latestStime[j];     
 
. . .

I already get the results, but they are not correct. As an example, if machine k starts from Order 3 going to  Order 1, the start service time of 1 must be greater than 3. but unfortunately in my results this is not the case.

thanks in advance.

best regards

Renato

Originally posted by: reru90

here is the complete model which i implemented

Originally posted by: reru90

Can someone help me, please((

The model/dat you attached do not work for me. Some things in the .dat are commented out and it seems this data is required to run the model.

Moreover, a lot of things in your .mod are commented out, so it is hard to read. Whenever you attach a model and data, make sure it actually works and also is clean.

In order to debug your modeling error I suggest to do the following:

1. Find variables that have incorrect values (like incorrect starting times)
2. Find the constraint that is supposed to exclude those variable settings
3. Figure out why the constraint does not exclude those settings.

If you cannot find a constraint in 2 then you are missing some constraint in your model. If you find the constraint then in 3 you will most likely be able to figure out what is missing.

Originally posted by: reru90

Hello Daniel, thank you very much for your help.
Unfortunately I have tried many times to find out the error. Actually the variables and contr. are right in my opinion. Herewith I post the model clearly and that already works but the startservicetimes working still not correct. You can look at "Erweiterung.mod" in the model and let it run.

Thanx again in advance for the answer.