ConstraintInstance¶

class ampl::ConstraintInstance : public ampl::BasicInstance<internal::ConstraintInstance>¶

This class represent an instance of a constraint.

In general, all AMPL suffixes for a constraint are available through methods with the same name in this class. See http://www.ampl.com/NEW/suffbuiltin.html for a list of the available suffixes.

Note that, since this class represents instances of both algebraic and logical constraints, some suffixes might not be available for every instance. If a wrong suffix for the specific class of constraint is accessed, an std::logic_error is thrown.

All the accessors in this class throw an std::runtime_error if the instance has been deleted in the underlying AMPL interpreter.

Public Functions

inline void drop()¶: Drop this constraint instance, corresponding to the AMPL code: drop constraintname;.

inline void restore()¶: Restore this constraint instance, corresponding to the AMPL code: restore constraintname;.

inline double body() const¶: Get the current value of the constraint’s body.

inline std::string astatus() const¶: Get the current AMPL status (dropped, presolved, or substituted out)

inline int defvar() const¶: Get the index in _var of “defined variable” substituted out by the constraint.

inline double dinit() const¶: Get the current initial guess for the constraint’s dual variable.

inline double dinit0() const¶: Get the original initial guess for the constraint’s dual variable.

inline double dual() const¶

Get the current value of the constraint’s dual variable.

Note that dual values are often reset by the underlying AMPL interpreter by the presolve functionalities triggered by some methods. A possible workaround is to set the option presolve; to false (see setBoolOption).

inline double lb() const¶: Get the current value of the constraint’s lower bound.

inline double ub() const¶: Get the current value of the constraint’s upper bound.

inline double lbs() const¶: Get the constraint lower bound sent to the solver (reflecting adjustment for fixed variables)

inline double ubs() const¶: Get the constraint upper bound sent to the solver (reflecting adjustment for fixed variables)

inline double ldual() const¶: Get the current dual value associated with the lower bound.

inline double udual() const¶: Get the current dual value associated with the upper bounds.

inline double lslack() const¶: Get the slack at lower bound body - lb

inline double uslack() const¶: Get the slack at upper bound ub - body

inline double slack() const¶: Constraint slack (the lesser of lslack and uslack)

inline std::string sstatus() const¶: Get the solver status (basis status of constraint’s slack or artificial variable)

inline std::string status() const¶: Get the AMPL status if not in, otherwise solver status.

inline void setDual(double dual)¶

Set the value of the dual variable associated to this constraint.

Equivalent to the AMPL statement:

let c := dual;

Parameters: dual – The value to be assigned to the dual variable

inline double val() const¶

Get the AMPL val suffix.

Valid only for logical constraints.

inline Entity entity() const¶: Returns the entity that this instance is part of.

inline Tuple key() const¶: Returns the key of this instance.

inline std::string name() const¶: Returns the name of this instance.

inline std::string toString() const¶: Returns a string representation of this instance.

Constraint

Objective