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.
Best answer by MarcelRoelofsView original
@mohansx ! Yes, I am using academic license. Thank you for the info!
@Shanice Hun Yee!
Just some side notes:
I hope that I could give you some useful pieces of advice.
@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.
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
TravelTimeis limited to say max 4 hours.
Index domain for variables
“By specifying the
IndexDomainattribute 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
IndexDomainattribute influences the matrix generation process. Constraints are generated only for those tuples in the index domain that satisfy the domain restriction.”
@Shanice Hun Yee
This morning we released AIMMS 126.96.36.199, 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).