Constraint¶

public class
Constraint
extends Entity<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
andConstraint.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 ofConstraintInstance
for indexed constraints).Note that, since this class represents both algebraic and logical constraints, some suffixes might not be available for every entity.
An
UnsupportedOperationException
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.The instances, represented by the class
ConstraintInstance
can be accessed via the methodConstraint.get
(see section Access to instances and values for further information on how to access instances).To gain access to all the values in an entity (for all instances and all suffixes for that entities), see
Entity.getValues
and theDataFrame
class.
Constructors¶
Methods¶
astatus¶
defvar¶

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

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

public double
dual
()¶ 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
(seeAMPL.setBoolOption
).
get¶

public ConstraintInstance
get
()¶ Get the constraint instance (to be used only on scalar constraints)
Throws:  UnsupportedOperationException – if the constraint is not scalar.
Returns: The corresponding instance. @ throws IllegalStateException if the constraint has been deleted in the underlying AMPL interpreter
get¶

public ConstraintInstance
get
(Object... key)¶ Get the constraint instance corresponding to the specified key. See Access to instances and values for further information on how the key can be specified.
Parameters:  key – The key to be found
Throws:  IllegalArgumentException – if trying to access an instance with the wrong number of keys (see
Entity.indexarity
)  IllegalStateException – if the entity has been deleted in the underlying AMPL interpreter
Returns: The constraint instance corresponding to the specified key. Returns
null
if the specified key is not present.
get¶

public ConstraintInstance
get
(Tuple key)¶ Get the constraint instance corresponding to the specified key, expressed as a Tuple. See Access to instances and values for further information on how the key can be specified.
Parameters:  key – The indexing Tuple of the instance to be found
Throws:  IllegalArgumentException – if trying to access an instance with the wrong indexarity (see
Entity.indexarity
)  IllegalStateException – if the entity has been deleted in the underlying AMPL interpreter
Returns: The constraint instance corresponding to the specified key. Returns
null
if the specified key is not present.
isLogical¶

public boolean
isLogical
()¶ 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
lbs¶

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

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

public 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
(seeAMPL.setBoolOption
).Parameters:  dual – The value to be assigned to the dual variable