lp_set(+Handle, ++What, +Value)

Handle

Handle to a solver state

What

Option to set

Value

Value being set

Description

This primitive can be used to change some of the initial options even after setup. Handle refers to an existing solver state, What can be one of the following:

method

Set the method that will be used to solve the problem. Value is one of default, primal, dual, net_primal, net_dual, barrier, barrier_primal, barrier_dual. Note that some of these methods may not be available on all external solvers. In case of MIP solving, this is the start algorithm (the one that is used to solve the initial relaxation).

solution

Make the solutions available each time the problem has been (re-)solved successfully. Value is one of the atoms yes or no.

reduced_cost

Make the reduced costs available each time the problem has been (re-)solved successfully. Value is one of the atoms yes or no.

slack

Make the constraint slacks available each time the problem has been (re-)solved successfully. Value is one of the atoms yes or no.

dual_solution

Make the dual solutions available each time the problem has been (re-)solved successfully. Value is one of the atoms yes or no.

keep_basis

Store the basis each time the problem has been solved successfully, and use this basis as a starting point for re-solving next time. Value is one of the atoms yes or no.

demon_tolerance

Specify how far outside a variable's range an lp-solution can fall before lp_demon_setup/6 re-triggers. Value is a comma-separated pair (RealTol,IntTol) of floating-point values (default (0.00001,0.5)).

simplify

Simplify the constraints before sending them to the external solver. The simplification consists of eliminating trivial constraints and turning simple constraints into bound updates. It is solver-dependent whether this step is needed or whether it is covered by the external solvers's preprocessing. Value is one of the atoms yes or no.

use_var_names

Specify if variable names (set using set_var_name/2 of the var_name library) should be passed to the external solver. If a particular variable does not have a name, a solver's default name would be used. Note that for XPRESS-MP, there is a limit on the length of the name, which can be changed between 8 and 64 in steps of 8 with the parameter N_NAMLEN. Variable names longer than this limit are truncated to the limit. Note also that only new variables from constraints added after the lp_set/3 call will pass their names to the external solver. Value is one of the atoms yes or no.

See Also