Re: vehicle routing problem time window

[Guido Diepen]

Hi,

to investigate the infeasibility, I would like to suggest you take a deeper look at the mathematical model that is actually sent to the solver. You can view this model either via the Math Program Inspector (Menu > Tools > Diagnostic Tools > Math Programming Inspector) or via the constraint listing, which is a text representation of your generated model. Instructions on how to switch on the constraint listing in AIMMS can be found in my blog post http://blog.aimms.com/2013/03/dealing-with-model-is-infeasible-or-unbounded-error/.

By carefully examining the generated model (and specifically the constraints service_76), you might find more insight as to what is causing the infeasibility.

Guido Diepen

AIMMS Specialist

On Thursday, May 16, 2013 7:57:55 AM UTC+2, Phannipa wrote:

Hi,

I am trying to use aims to solve a VRPTW in The vehicle routing problem.. P. Toth, D. Vigo. Pages:158 - 159.

http://books.google.co.uk/books?id=TeMgA5S74skC&printsec=frontcover&hl=th&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

 

Here are the problems I have encountered.

1)         When I run the solver, I get the message: Warning: After zero iterations CPLEX 12.5 concluded that an integer solution to MinCost does not exist.

 

2)         When I removed  constraint service_76  and run the solver, I get the solution of  xkij but it has a sub tour.

 

I'm not sure about the commands or syntax I used in Aimms. Since I have just learned to use it,  I must have done something wrong.  Could you help me to figure out how to solve the problem (Toth, p 158-159)?