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AIMMS Shut Down Its Own


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Good morning and a very good day to you!

Dear Sir / Madam,

Currently, I am running big data using AIMMS for my Final Year Project to produce an optimal exam timetable. My MIP model consists of 1 decision variable, 3 objective functions and 14 constraints.

I encountered the same problem for many times when I was running my data. I realized that AIMMS will usually shut down on its own after running for more than 2 hours before even getting the results. I have checked my computer to see if it has any technical problems but I have not found any. Can you please help me with this problem? 

I am attaching a relevant picture for your further references. I am looking forward to getting a favorable reply from you soon. Thank you for your time and patience.

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Best answer by MarcelRoelofs 28 May 2021, 14:51

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).

 

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Userlevel 5
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@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

 

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

Userlevel 2
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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 

Userlevel 6
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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

 

Userlevel 3
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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).

 

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@Zsolt Mihály @Gertjan @MarcelRoelofs Thank you for the advices. I will keep trying until I get my result. :muscle_tone1:

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