The Linear Programming Solver

LP Solver Options

This section describes the options recognized by the LP solver. These options can be specified after a forward slash (/) in the SOLVE statement, provided that the LP solver is explicitly specified using a WITH clause.

If the LP solver terminates before reaching an optimal solution, an intermediate solution is available. You can access this solution by using the .sol variable suffix in the OPTMODEL procedure. See the section Suffixes for details.

Solver Options

ALGORITHM=option SOLVER=option SOL=option

specifies an LP algorithm. You can specify the following options:

PRIMAL (PS): uses the primal simplex algorithm.
DUAL (DS): uses the dual simplex algorithm.
NETWORK (NS): uses the network simplex algorithm.
INTERIORPOINT (IP): uses the interior point algorithm.
CONCURRENT (CON): uses several different algorithms in parallel.
SIFTING (SIFT): uses the sifting algorithm.
SIMPLEX (SPX): uses one of the simplex-based algorithms: PS, DS, NS, and SIFT. The algorithm is determined automatically on the basis of the problem structure.

The valid abbreviated value for each option is indicated in parentheses. By default, ALGORITHM=SIMPLEX.

ALGORITHM2=option SOLVER2=option

specifies an LP algorithm if ALGORITHM=NS. You can specify the following values:

PRIMAL (PS): uses the primal simplex algorithm (after network simplex).
DUAL (DS): uses the dual simplex algorithm (after network simplex).

The valid abbreviated value for each option is indicated in parentheses. By default, the LP solver decides which algorithm is best to use after calling the network simplex algorithm on the extracted network.

IIS=FALSE | TRUE

specifies whether the LP solver attempts to identify a set of constraints and variables that form an irreducible infeasible set (IIS). You can specify the following values:

FALSE: disables IIS detection.
TRUE: enables IIS detection.

If an IIS is found, information about infeasible constraints or variable bounds can be found in the .status values of the constraints and variables. For more information about the .status suffix, see the section Suffixes. For more information about IIS, see the section Irreducible Infeasible Set. By default, IIS=FALSE.

Presolve Options

DUALIZE=AUTOMATIC | OFF | ON

controls the dualization of the problem. You can specify the following values:

AUTOMATIC: specifies that the presolver use a heuristic to decide whether to dualize the problem or not.
OFF: disables dualization. The optimization problem is solved in the form that you specify.
ON: specifies that the presolver formulate the dual of the linear optimization problem.

Dualization is usually helpful for problems that have many more constraints than variables. You can use this option with all simplex algorithms in the SOLVE WITH LP statement, but it is most effective with the primal and dual simplex algorithms.

By default, DUALIZE=AUTOMATIC.

FOLD=AUTOMATIC | OFF | ON

controls the folding of the problem. You can specify the following values:

AUTOMATIC: specifies that the presolver use a heuristic to decide whether to fold the problem or not.
OFF: disables folding. The optimization problem is not further reduced by folding.
ON: specifies that the presolver try to fold the linear optimization problem.

Folding is helpful for problems that have a symmetric structure. When you use this option with a simplex algorithm in the SOLVE WITH LP statement, a crossover step must be used to find a basic solution.

By default, FOLD=AUTOMATIC.

specifies the level of presolve processing. You can specify the following values:

AUTOMATIC: applies the presolver by using the default settings. Suitable limits are in place such that the presolver reduces the problem almost as much as when PRESOLVER=AGGRESSIVE, but in a reasonable time.
NONE: disables the presolver. Only the necessary problem transformation steps are performed.
BASIC: performs a basic presolve, such as removing empty rows, columns, and fixed variables. Only some very fast operations are performed.
MODERATE: performs a basic presolve and applies other inexpensive presolve techniques. Suitable limits are in place such that the presolver reduces the problem almost as much as when PRESOLVER=AGGRESSIVE, but in a reasonable time.
AGGRESSIVE: performs a moderate presolve and applies other aggressive (but computationally expensive) presolve techniques. All the presolver techniques are called with no limits. This reduces the problem the most, but can take a very long time.

By default, PRESOLVER=AUTOMATIC. For more information, see the section Presolve.

Control Options

FEASTOL=

specifies the feasibility tolerance [1E–9, 1E–4] for determining the feasibility of variable and constraint values. The default value is 1E–6. Both simplex and interior point algorithms use the relative error for the computation of feasibility tolerance.

LOGFREQ=k PRINTFREQ=k

specifies that the printing of the solution progress to the iteration log is to occur after every k iterations. The print frequency, k, is an integer between zero and the largest four-byte signed integer, which is .

The value k = 0 disables the printing of the progress of the solution.

If the LOGFREQ= option is not specified, then the LP solver displays the iteration log with a dynamic frequency according to the problem size if the primal or dual simplex algorithm is used, with frequency 10,000 if the network simplex algorithm is used, or with frequency 1 if the interior point algorithm is used.

LOGLEVEL=NONE | BASIC | MODERATE | AGGRESSIVE

controls the amount of information that the LP solver displays in the SAS log, from a solver summary to details at each iteration. You can specify the following values:

NONE: turns off all solver-related messages in the SAS log.
BASIC: displays a solver summary after stopping.
MODERATE: prints a solver summary and an iteration log by using the value that you specify in the LOGFREQ= option.
AGGRESSIVE: prints a detailed solver summary and an iteration log by using the value that you specify in the LOGFREQ= option.

By default, LOGLEVEL=MODERATE.

MAXITER=k

specifies the maximum number of iterations. The value k can be any integer between one and the largest four-byte signed integer, which is . If you do not specify this option, the procedure does not stop based on the number of iterations performed. For network simplex, this iteration limit corresponds to the algorithm called after network simplex (either primal or dual simplex).

MAXTIME=t

specifies an upper limit of t units of time for the optimization process, including problem generation time and solution time. The value of the TIMETYPE= option determines the type of units used. If you do not specify this option, the solver does not stop based on the amount of time elapsed. The value of t can be any positive number; the default value is the positive number that has the largest absolute value that can be represented in your operating environment.

OPTTOL=

specifies the optimality tolerance [1E–9, 1E–4] for declaring optimality. The default value is 1E–6. Both simplex and interior point algorithms use the relative error for the computation of optimality tolerance.

TIMETYPE=CPU | REAL

specifies the units of time used by the MAXTIME= option and reported by the PRESOLVE_TIME and SOLUTION_TIME terms in the _OROPTMODEL_ macro variable. You can specify the following values:

CPU: specifies units of CPU time.
REAL: specifies units of real time.

By default, TIMETYPE=REAL.

Simplex Algorithm Options

BASIS=CRASH | SLACK | WARMSTART

specifies the option for generating an initial basis. You can specify the following values:

CRASH: generates an initial basis by using crash techniques (Maros 2003). The procedure creates a triangular basic matrix consisting of both decision variables and slack variables.
SLACK: generates an initial basis by using all slack variables.
WARMSTART: starts the primal and dual simplex algorithms with the available basis.

The default option is determined automatically based on the problem structure. For network simplex, this option has no effect.

PRICETYPE=DEVEX | FULL | HYBRID | PARTIAL | STEEPESTEDGE

specifies the pricing strategy for the primal and dual simplex algorithms. You can specify the following values:

DEVEX: uses the Devex pricing strategy.
FULL: uses Dantzig’s rule on all decision variables.
HYBRID: uses a hybrid of the Devex and steepest-edge pricing strategies. This strategy is available only for the primal simplex algorithm.
PARTIAL: uses Dantzig’s rule on a queue of decision variables. Optionally, you can specify QUEUESIZE=k. This strategy is available only for the primal simplex algorithm.
STEEPESTEDGE: uses the steepest-edge pricing strategy.

The default option is determined automatically according to the problem structure. For the network simplex algorithm, this option applies only to the algorithm that is specified in the ALGORITHM2= option. For more information, see the section Pricing Strategies for the Primal and Dual Simplex Algorithms.

QUEUESIZE=k

specifies the queue size , where n is the number of decision variables. This queue is used for finding an entering variable in the simplex iteration. The default value is chosen adaptively based on the number of decision variables. This option is used only when PRICETYPE=PARTIAL.

SCALE=AUTOMATIC | NONE

specifies a scaling option. You can specify the following values:

AUTOMATIC: automatically applies scaling procedure if necessary.
NONE: disables scaling.

By default, SCALE=AUTOMATIC.

SEED=number

specifies the initial seed for the random number generator. Because the seed affects the perturbation in the simplex algorithms, the result might be a different optimal solution and a different solver path, but the effect is usually negligible. The value of number can be any positive integer up to the largest four-byte signed integer, which is . By default, SEED=100.

Interior Point Algorithm Options

CROSSOVER=FALSE | TRUE

specifies whether to convert the interior point solution to a basic simplex solution. If the interior point algorithm terminates with a solution, the crossover algorithm uses the interior point solution to create an initial basic solution. After performing primal fixing and dual fixing, the crossover algorithm calls a simplex algorithm to locate an optimal basic solution.

You can specify the following values:

FALSE: does not convert the interior point solution to a basic simplex solution.
TRUE: converts the interior point solution to a basic simplex solution.

By default, CROSSOVER=TRUE.

DUALITYGAP=

specifies the desired relative duality gap [1E–9, 1E–4], which is the relative difference between the primal and dual objective function values and is the primary solution quality parameter. For more information, see the section The Interior Point Algorithm. The default value is 1E–6.

Parallel Options

The LP solver has several components that take advantage of shared-memory parallel architectures. You can use the following options to control parallel processing:

DETERMINISTIC=TRUE | FALSE

specifies whether to run the LP solver in deterministic or nondeterministic parallel mode. You can specify the following values:

TRUE: runs the LP solver in deterministic parallel mode.
FALSE: runs the LP solver in nondeterministic parallel mode.

By default, DETERMINISTIC=TRUE.

NTHREADS=number

specifies the maximum number of threads for the LP solver to use for multithreaded processing. The value of number can be any integer between 1 and 256, inclusive. The default is the value of the NTHREADS= option in PROC OPTMODEL.

Sensitivity Analysis Option

The following option enables sensitivity analysis in the LP solver:

SENSITIVITY=(options)

enables sensitivity analysis and specifies overall control options for the algorithm. You can specify the following options:

CHANGE=(ALL LB OBJ RANGE RHS UB)

specifies which parts of the problem data to run the sensitivity analysis algorithm on. You can specify the following values:

ALL: runs sensitivity analysis on all the supported pieces of the input data.
LB: runs sensitivity analysis on the variable lower bounds.
OBJ: runs sensitivity analysis on the objective coefficients.
RANGE: runs sensitivity analysis on the range row bounds.
RHS: runs sensitivity analysis on the row right-hand sides.
UB: runs sensitivity analysis on the variable upper bounds.

This is a required option with no default value.

For more information about sensitivity analysis, see the section Sensitivity Analysis.

Dantzig-Wolfe Decomposition Algorithm Options

The following options are available for the Dantzig-Wolfe decomposition algorithm in the LP solver. For information about the Dantzig-Wolfe decomposition algorithm, see Chapter 19, The Dantzig-Wolfe Decomposition Algorithm.

DECOMP=(options): enables the Dantzig-Wolfe decomposition algorithm and specifies overall control options for the algorithm. For more information about this option, see Chapter 19, The Dantzig-Wolfe Decomposition Algorithm.
DECOMPMASTER=(options): specifies options for the master problem. For more information about this option, see Chapter 19, The Dantzig-Wolfe Decomposition Algorithm.
DECOMPSUBPROB=(options): specifies option for the subproblem. For more information about this option, see Chapter 19, The Dantzig-Wolfe Decomposition Algorithm.

Last updated: September 09, 2026