CPLEX Limit Parameter Options

You can change the Limit options for CPLEX by choosing CPLEX parameters from the Options menu and then pressing the Limits tab. This will display the dialog box shown below:

List of Options

Description of Options

Time Limit:

The Time limit option used to set maximum time (in hours:min:sec) for computations before termination. The time limit applies to primal simplex, dual simplex, barrier, and mixed integer optimizations, as well as infeasibility finder computations.

Iteration Limit

The Iteration limit sets the maximum number of iterations before the algorithm terminates, without reaching optimality. Be sure to enter only an integer value. The default value is 2100000000.

Pricing Candidate List Size

Contains the maximum number of variables kept in the pricing candidate list. If the value is zero the number is determined automatically at run-time.

Singularity Limit

The Singularity limit value restricts the number of times CPLEX will attempt to repair the basis when singularities are encountered. Once the limit is exceeded, CPLEX replaces the current basis with the best factorizable basis that has been found. At this point the user can examine and modify the problem or increase the singular limit to force CPLEX to work harder at eliminating singularities. The default value is 10.

Object Value Lower Limit

Setting a lower objective function limit will cause CPLEX to halt the optimization process once the minimum objective function value limit has been exceeded. This limit applies only during Phase II of the optimization.

Object Value Upper Limit

Setting a upper objective function limit will cause CPLEX to halt the optimization process once the maximum objective function value limit has been exceeded. This limit applies only during Phase II of the optimization.

MIP Solutions limit

The MIP solutions limit value limits the mixed integer optimization to finding only this number of mixed integer solutions before stopping. The default value is 2100000000.

Node limit

The Node limit value sets the maximum number of nodes solved before the algorithm terminates, without reaching optimality. The default value is 2100000000.

Tree Memory Limit

The Tree memory limit value sets an upper limit on the amount of memory (in megabytes) that the branch-and-bound tree can consume. CPLEX will terminate optimization when the amount of memory required to store branch-and-bound information exceeds the tree memory parameter setting.

Min SOS size

The Min SOS size parameter is used to set the minimum size for sets found during the scan for SOS Type 3 sets. The SOS algorithm may not be worthwhile on smaller size sets. The default value is 2.

Node File Size Limit

The Node File Size Limit option limits the size of the node file.

Strong Branching Cand Limit

Controls the length of the candidate list when using the "strong branching" variable selection setting.

Strong Branching Iter Limit

Controls the number of simplex iterations performed on each variable in the candidate list when using the "strong branching" variable selection setting. The default setting 0 chooses the iteration limit automatically.

Strong Branching Thread Limit

Controls the number of parallel threads used to perform strong branching. This parameter does nothing if the MIP thread limit is greater than 1.

MIP Node File

The MIP Node File is used when the tree memory limit is reached. If no node file is selected the optimization is terminated when the tree memory limit is reached. Otherwise, a group of nodes is removed from the in-memory set, and transferred to a node file. This group of nodes is returned to the in-memory set as needed.

Node files are used most efficiently when the amount of tree memory is reasonably large, so that the node files do not have to be formed too frequently. The compression options require a small amount of extra time due to the extra processing but since they result in smaller node files the overall systems is smaller and the system throughput may increase.