GLPK Parameter Options

List of Options

Description of Options

Algorithm

Indicates which algorithm type to use when solving LPs.

Message level

Controls the level of the log output.

Scaling process

Specifies which scaling method to employ.

Use Dual Simplex

Boolean option whether to use the Dual Simplex method to solve LPs.

Pricing strategy

Sets the pricing strategy for both the Primal and Dual Simplex algorithms.

Relaxation

Relaxation parameter used in the ratio test. If it is zero, the textbook ratio test is used. If it is non-zero (should be positive), Harris' two-pass ratio test is used. In the latter case on the first pass of the ratio test basic variables (in the case of primal simplex) or reduced costs of non-basic variables (in the case of dual simplex) are allowed to slightly violate their bounds, but not more than the feasibility tolerance or the dual feasibility tolerance (thus, the parameter is a percentage of the feasibility or dual feasibility tolerances).

Feasibility tolerance

Relative tolerance used to check if the current basic solution is primal feasible.

Dual feasibility tolerance

Absolute tolerance used to check if the current basic solution is dual feasible.

Pivot tolerance

Relative tolerance used to choose eligible pivotal elements of the simplex table.

Solution rounding

Sets which solution rounding option.

Objective lower limit

Lower limit of the objective function. If on the phase II the objective function reaches this limit and continues decreasing, the solver stops the search. (Used in the dual simplex only.).

Objective upper limit

Upper limit of the objective function. If on the phase II the objective function reaches this limit and continues increasing, the solver stops the search. (Used in the dual simplex only).

Iteration limit

Simplex iterations limit. If this value is positive, it is decreased by one each time when one simplex iteration has been performed, and reaching zero value signals the solver to stop the search. Negative value means no iterations limit.

Time limit

Searching time limit, in seconds. If this value is positive, it is decreased each time when one simplex iteration has been performed by the amount of time spent for the iteration, and reaching zero value signals the solver to stop the search. Negative value means no time limit.

Log output frequency

Output frequency, in iterations. This parameter specifies how frequently the solver sends information about the solution to the log output.

Log output delay

Output delay, in seconds. This parameter specifies how long the solver should delay sending information about the solution to the output device. Non-positive value means no delay.

Variable Selection

The variable selection option is used to set the rule for selecting the branching variable.

Backtracking method

The node selection option is used to set the rule for selecting the next node to process when backtracking.

Integral feasible tolerance

Absolute tolerance used to check if the current basic solution is integer feasible.

Relative objective gap

Relative tolerance used to check if the value of the objective function is not better than in the best known integer feasible solution.

Write comment cards

Is a boolean option that writes out several comment cards, which contains some information about the problem in MPS format. Otherwise the routine writes no comment cards.

Relaying objective

This parameter tells how to relay the objective function row.

Use original names

A flag that sets whether to uses the original symbolic names of rows and columns. Otherwise uses plain names using ordinal numbers of rows and columns.

Use MPS Wide format

If this flag is set, GLPK mps writing routine uses all data fields.

Use MPS freestyle format

A flag that chooses whether to omit row and column names when possible in writing out an MPS file.

Use MPS SkipEmpty format

If this flag is set, GLPK mps writing routine skips empty columns (i.e. which has no constraint coefficients). Otherwise the routine outputs all columns.

Use Presolve

Boolean option thats sets whether GLPK utilizes the built-in LP presolver.

Binarize discrete variables

Boolean option that replaces general integer variables by binary ones.

Cutting plane settings

Is a bitwise operator that determines whether specifc cutting planes are added to the MIP problem. The bitwise inclusive OR of the following values: