@Shanice Hun Yee are you using an academic license ? if yes, perhaps your computer is losing internet connection during the solve. See The need for internet connection while running AIMMS | AIMMS Community

Hi @mohansx ! Yes, I am using academic license. Thank you for the info!

Hi @Shanice Hun Yee!

Just some side notes:

1. As I look at your picture, it shows that you have ~7 million constraints and ~500k integer variables. To solve a model of this size can take a really long time.
2. What you experience can occur if all the RAM is used up by the solver. As a good practice, I would suggest you to always set a time limit / gap limit for the solver (in case you haven’t done it so far).

I hope that I could give you some useful pieces of advice.

Kr,
Zsolti 

Hi @Shanice Hun Yee 

In addition to @Zsolt Mihály’s remark on the model size I wonder if your model is possibly unnecessary large. Can it be limited by applying ‘Domain Restrictions’ to the variables and constraints. If you can, it might have a big impact on both model size and performance. 
 

E.g. variable Transport(i,j) | (RoadExists(i,j) and TravelTime(i,j) <=4) to only consider possible values for direct connections that can actually be travelled and where TravelTime is limited to say max 4 hours.

Extra info. 

Index domain for variables

“By specifying the IndexDomain attribute you can restrict the domain of a variable in the same way as that of a parameter. For variables, however, the domain restriction has an additional effect. During the generation of individual constraints AIMMS will reduce the size of the generated mathematical program by including only those variables that satisfy all domain restrictions.”

Domain restriction for constraints

“Restricting the domain of constraints through the IndexDomain attribute influences the matrix generation process. Constraints are generated only for those tuples in the index domain that satisfy the domain restriction.”

https://documentation.aimms.com/language-reference/optimization-modeling-components/variable-and-constraint-declaration/variable-declaration-and-attributes.html

https://documentation.aimms.com/language-reference/optimization-modeling-components/variable-and-constraint-declaration/constraint-declaration-and-attributes.html

Hi @Shanice Hun Yee 

This morning we released AIMMS 4.79.6.12, which contains a number of improvements wrt loss of licensing connectivity and automatic re-connection, in case that was the cause of your shutdown solver sessions. 

You can download it from the AIMMS Launcher (or manually if you so prefer).

@Zsolt Mihály @Gertjan @MarcelRoelofs Thank you for the advices. I will keep trying until I get my result.