Terminated by The Solver

Thank you @Marcel Hunting for the recommendations. I’d like to understand if this issue is solely due to CPLEX running out of memory, or if there might be other factors contributing to the problem. Could you provide further insights into possible alternative causes that could lead to the issues?

Best regards,
Wanie Saidi

Where is the option to open the log folder in AIMMS?

Is it this folder?

This is the CPLEX status file that I got after the model stopped running. Solver status shows ‘Terminated by Solver’ with the gap 0.15%. It seems that it is because there is not enough memory from the CPLEX status file. Can you give a detailed explanation about the other information in this status file?

The CPLEX status file indeed shows that CPLEX ran out of memory.

The status file shows the type of cutting planes (cuts) that were added while solving the model. The warning about MIP starts not constructed seems incorrect because MIP starts are used (if enabled) at the beginning of the solve when CPLEX should still have sufficient memory.

You did not show the beginning of the CPLEX status file while it contains very useful information about the CPLEX presolver, e.g., the model size after presolving the model.

There are some ways to reduce the memory usage by CPLEX:

1. Enabling the AIMMS Presolver, by switching on the Solvers General option ‘Linear presolve’, sometimes helps to (drastically) reduce the memory usage by CPLEX. For this you need AIMMS 4.89 or newer. Preferably AIMMS 4.96 or newer because there have been some improvements for the AIMMS Presolver between AIMMS 4.89 and 4.96.
2. Set the CPLEX option ‘Node file’ to 'On disk and compressed'. However, your hard disk should then have sufficient free space; at least 70 Gb but more preferably.
3. Reduce the number of threads used by CPLEX by setting the CPLEX option ‘Global thread limit’ to 16. However, this likely will increase the solving time.
4. Make the model formulation more tight such that CPLEX needs less nodes to solve the model. But this is not easy. See the paper Practical guidelines for solving difficult mixed integer linear programs by Ed Klotz and Alexandra M.Newman (2013) for more information.

Enabling the AIMMS Presolver would only be useful if the CPLEX status file shows that the CPLEX presolver drastically reduced the model size.

​​​​​​(1) You can download older AIMMS versions from here. After installing AIMMS 4.96 (or newer) you can just open the project with AIMMS 4.96.

(2) CPLEX uses threads to solve the problem in parallel on multiple cores. In general using more threads results in a better performance but with a higher memory consumption. The CPLEX option 'Global thread limit’ controls the amount of threads used by CPLEX. The value 0 means that the number of threads used is set equal to the number of (logical) cores in the computer.

(3) A gap of 0.08% means that the objective value found is within 0.08% of the optimal objective value. (So, in theory, CPLEX could find an objective value that is 0.08% better if it would have been able to solve the model to optimality.) If you want to limit the solution to 5% then you should set the 'MIP Relative Optimality Tolerance' to 0.05.

(4) You should install an incumbent callback which is called whenever CPLEX finds a new integer feasible solution, which can be stored in AIMMS. After the solve, the last of these solutions can be restored. See the attached example.