Constraint¶

class
ampl::
Constraint
¶ 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 nonscalar 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

InstanceClass
get
() const¶ Get the instance corresponding to a scalar entity.
 Return
 The corresponding instance.
 Exceptions
runtime_error
if the entity has been deleted in the underlying AMPL interpreter
logic_error
if the entity is not scalar

InstanceClass
get
(TupleRef index) const¶ Get the instance with the specified index.
 Return
 The corresponding instance
 Parameters
index
The tuple specifying the index
 Exceptions
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

InstanceClass
get
(VariantRef v1) const¶

InstanceClass
get
(VariantRef v1, VariantRef v2) const¶

InstanceClass
get
(VariantRef v1, VariantRef v2, VariantRef v3) const¶

InstanceClass
get
(VariantRef v1, VariantRef v2, VariantRef v3, VariantRef v4) const¶ Get the instance with the specified index.
 Return
 The corresponding instance
 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
 Exceptions
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

InstanceClass
operator[]
(VariantRef v1) const¶
Public Types

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

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”.
 Return
 True if logical

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

void
restore
()¶ Restore all instances in this constraint entity, corresponding to the AMPL code:
restore constraintname;

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

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

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

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

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

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;
tofalse
(see setBoolOption).

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

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

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

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

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

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

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

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

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

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

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

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;
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
tofalse
(see setBoolOption). Parameters
dual
The value to be assigned to the dual variable

double
val
() const¶ Get the AMPL val suffix.
Valid only for logical constraints.

iterator
find
(TupleRef t) const¶ Searches the current entity for an instance with the specified index.
 Return
 an iterator to the wanted entity if found, otherwise an iterator to BasicEntity::end.

InstanceClass