Constraint¶

class ampl::Constraint : public ampl::BasicEntity<ConstraintInstance>¶

This class represents an algebraic or logical constraint.

In case the constraint is scalar, its values can be accessed via functions like Constraint::body and Constraint::dual. All the AMPL suffixes for constraints (see http://www.ampl.com/NEW/suffbuiltin.html) are available through methods of this class with the same name (and methods of ConstraintInstance for indexed constraints).

Note that, since this class represents both algebraic and logical constraints, some suffixes might not be available for every entity.

An std::logic_error is thrown if one of such methods is called for a non-scalar constraint and if a method corresponding to a suffix which is not supported by the type of the constraint is called. A runtime error is thrown if any property of an entity which has been deleted from the underlying interpreter is accessed.

The instances, represented by the class ConstraintInstance can be accessed via the operator Constraint::operator[](), via the methods Constraint::get() or via the iterators provided.

To gain access to all the values in an entity (for all instances and all suffixes for that entities), see Entity::getValues() and the ampl::DataFrame class.

Instance access

Methods to access the instances which are part of this Entity

inline ConstraintInstance get() const¶

Get the instance corresponding to a scalar entity.

Throws

runtime_error – if the entity has been deleted in the underlying AMPL interpreter
logic_error – if the entity is not scalar

Returns

The corresponding instance.

inline ConstraintInstance get(TupleRef index) const¶

Get the instance with the specified index.

Parameters

index – The tuple specifying the index

Throws

out_of_range – if an instance with the specified index does not exist
out_of_range – if the entity has been deleted in the underlying AMPL interpreter
ampl::UnsupportedOperationException – if the entity is scalar

Returns

The corresponding instance

inline ConstraintInstance get(VariantRef v1) const¶: Get the instance with the specified index.

inline ConstraintInstance get(VariantRef v1, VariantRef v2) const¶: Get the instance with the specified index.

inline ConstraintInstance get(VariantRef v1, VariantRef v2, VariantRef v3) const¶: Get the instance with the specified index.

inline ConstraintInstance get(VariantRef v1, VariantRef v2, VariantRef v3, VariantRef v4) const¶

Get the instance with the specified index.

Parameters

v1 – The VariantRef specifying the first element of the indexing tuple
v2 – The VariantRef specifying the second element of the indexing tuple
v3 – The VariantRef specifying the third element of the indexing tuple
v4 – The VariantRef specifying the fourth element of the indexing tuple

Throws

out_of_range – if an instance with the specified index does not exist
runtime_error – if the entity has been deleted in the underlying AMPL interpreter
ampl::UnsupportedOperationException – if the entity is scalar

Returns

The corresponding instance

inline ConstraintInstance operator[](TupleRef index) const¶

inline ConstraintInstance operator[](VariantRef v1) const¶

Public Types

typedef internal::CountedIterator<internal::EntityWrapper<ConstraintInstance>> iterator¶: Iterator for entities, represented by an iterator pointing to elements of type std::pair<TupleRef, InstanceClass>

Public Functions

inline bool isLogical() const¶

Check if the constraint is a logical constraint.

The available suffixes differ between logical and non logical constraints. See http://www.ampl.com/NEW/suffbuiltin.html

for a list of the available suffixes for algebraic constraints. The suffixes available for logical constraints are marked on the method description by “Valid only for logical

constraints”.

Returns: True if logical

inline void drop()¶: Drop all instances in this constraint entity, corresponding to the AMPL code: drop constraintname;

inline void restore()¶: Restore all instances in this constraint entity, 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 (valid only if the constraint is scalar).

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 iterator begin() const¶: Get an iterator pointing to the first instance in this entity.

inline iterator end() const¶: Get an iterator pointing after the last instance in this entity.

inline iterator find(TupleRef t) const¶

Searches the current entity for an instance with the specified index.

Returns: an iterator to the wanted entity if found, otherwise an iterator to BasicEntity::end.

inline StringArray getIndexingSets() const¶

Get the AMPL string representation of the sets on which this entity is indexed.

The obtained vector can be modified without any effect to the entity.

Returns: The string representation of the indexing sets for this entity or an empty array if the entity is scalar

inline DataFrame getValues() const¶

Get the principal values of this entity as a DataFrame. The specific returned value depends on the type of entity (see list below).

For:

Variables and Objectives it returns the suffix val
Parameters it returns their values
Constraints it returns the suffix dual
Sets it returns all the of the set. Note that it does not
apply to indexed sets. See SetInstance::getValues

Returns: A DataFrame containing the values for all instances

inline DataFrame getValues(StringArgs suffixes) const¶

Get the specified suffixes value for all instances in a DataFrame.

Parameters: suffixes – Suffixes to get
Returns: A DataFrame containing the specified values

inline std::size_t indexarity() const¶

Get the indexarity of this entity (sum of the dimensions of the indexing sets).

This value indicates the arity of the Tuple to be passed to the method BasicEntity::get() in order to access an instance of this entity. See the following AMPL examples

var x;               # indexarity = 0
var y {1..2};        # indexarity = 1
var z {1..2,3..4};   # indexarity = 2
var zz {{(1, 2)}};   # indexarity = 2

Returns: The sum of the dimensions of the indexing sets or 0 if the entity is not indexed

inline bool isScalar() const¶

Check whether this entity is scalar.

Equivalent to testing whether indexarity() is equal to zero.

Returns: True if the entity is scalar (not indexed over any set)

inline std::string name() const¶: Get the name of this entity.

inline std::size_t numInstances() const¶: Get the number of instances in this entity.

inline void setValues(DataFrame data)¶

Set the values of this entiy to the correponding values of a DataFrame indexed over the same sets (or a subset). This function assigns the values in the first data column of the passed dataframe to the entity the function is called from. In particular, the statement:

x.setValues(y.getValues());

is semantically equivalent to the AMPL statement:

let {s in S} x[s] := y[s];

Parameters: data – The data to set the entity to

inline std::string toString() const¶: Returns a string representation of this entity (its declaration)

inline StringArray xref() const¶

Get the names of all entities which depend on this one.

Returns: An array with the names of all entities which depend on this one.

Instance

ConstraintInstance