lp_get(+Handle, ++ParamName, -Value)

Handle

Handle to an exisiting solver state

ParamName

Name of parameter (atom)

Value

Returned value for ParamName

Description

Retrieve information about solver state and results for the solver state represented by Handle. ParamName is the same as that for eplex_get/2, which retrieves the same information via the EplexInstance. It can be one of:

vars

Returns a term ''(X1,...,Xn) whose arity is the number of variables involved in the solver's constraint set, and whose arguments are these variables.

ints

Returns a list [Xi1,...,Xik] which is the subset of the problem variables that the solver considers to be integers.

constraints_norm

Returns a list of the problem constraints in normalised form. They may be simplified with respect to the original set that was passed to lp_setup/4.

constraints

Returns a list of the problem constraints in denormalised (readable) form. They may be simplified with respect to the original set that was passed to lp_setup/4.

objective

Returns a term min(E) or max(E), representing objective function and optimisation direction. E is a linear expression.

method

Returns the method (default, primal, dual, net_primal, net_dual, barrier, barrier_primal, barrier_dual) that is used to solve the problem. In case of MIP solving, this is the start algorithm (the one that is used to solve the initial relaxation).

status

Status that was returned by the most recent invocation of the external solver.

cost

Cost of the current solution. Fails if no solution has been computed yet.

typed_solution

Returns a term ''(X1,...,Xn) whose arguments are the properly typed (integer or float) solution values for the corresponding problem variables (vars). The floating point solutions are the same as returned by solution, the integers are obtained by rounding the corresponding floating-point solution to the nearest integer. To instantiate the problem variables to their solutions, unify this term with the corresponding term containing the variables:

    instantiate_solution(Handle) :-
        lp_get(Handle, vars, Vars),
        lp_get(Handle, typed_solution, Values),
        Vars = Values.

slack

Returns a list of floating-point values representing the constraint slacks. The order corresponds to the list order in constraints. Fails if no solution has been computed yet.

dual_solution

Returns a list of floating-point values representing the dual solutions. The order corresponds to the list order in constraints. Fails if no solution has been computed yet.

demon_tolerance

Returns a comma-separated pair (RealTol,IntTol) of floating-point values which specify how far outside a variable's range an lp-solution can fall before lp_demon_setup/6 re-triggers. The tolerances differ for real (default 0.00001) and integer (default 0.5) variables.

simplex_iterations

Returns the external solver's count of simplex iterations.

node_count

Returns the external MIP solver's node count.

statistics

Returns a list of counter values [Successes, Failures, Aborts], indicating how often lp_solve/2 was invoked on the Handle, and how many invocations succeeded, failed and aborted respectively.

pool

Returns the name of the eplex instance (if any) associated with the solver state. Fails otherwise. Only useful if called with lp_get/3.

handle

Returns the solver state handle (if any) associated with the eplex instance. Fails otherwise. Only useful if called with eplex_get/2.

See Also