ConstraintInstance¶
- class 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 https://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 error is thrown.
All the accessors in this class throw an error if the instance has been deleted in the underlying AMPL interpreter.
- ConstraintInstance.name()¶
Returns the name of this instance.
- Returns
Name of the instance.
- ConstraintInstance.toString()¶
Returns a string representation of this instance.
- Returns
String representation of this instance.
- ConstraintInstance.drop()¶
Drop this constraint instance, corresponding to the AMPL code: drop constraintname;
- ConstraintInstance.restore()¶
Restore this constraint instance, corresponding to the AMPL code: restore constraintname;
- ConstraintInstance.body()¶
Get the current value of the constraint’s body.
- Returns
The current value of the constraint’s body.
- ConstraintInstance.astatus()¶
Get the current AMPL status (dropped, presolved, or substituted out).
- Returns
The current AMPL status.
- ConstraintInstance.defvar()¶
Get the index in _var of “defined variable” substituted out by the constraint.
- Returns
The index of the variable substituted out by the constraint.
- ConstraintInstance.dinit()¶
Get the current initial guess for the constraint’s dual variable.
- Returns
The current initial guess for the constraint’s dual variable.
- ConstraintInstance.dinit0()¶
Get the original initial guess for the constraint’s dual variable.
- Returns
The original initial guess for the constraint’s dual variable.
- ConstraintInstance.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; to false (see
setOption
).- Returns
The current value of the constraint’s dual variable.
- ConstraintInstance.lb()¶
Get the current value of the constraint’s lower bound.
- Returns
The current value of the constraint’s lower bound.
- ConstraintInstance.ub()¶
Get the current value of the constraint’s upper bound.
- Returns
The current value of the constraint’s upper bound.
- ConstraintInstance.lbs()¶
Get the constraint lower bound sent to the solver (reflecting adjustment for fixed variables).
- Returns
The constraint lower bound sent to the solver.
- ConstraintInstance.ubs()¶
Get the constraint upper bound sent to the solver (reflecting adjustment for fixed variables).
- Returns
The constraint upper bound sent to the solver.
- ConstraintInstance.ldual()¶
Get the current dual value associated with the lower bound.
- Returns
The current dual value associated with the lower bound.
- ConstraintInstance.udual()¶
Get the current dual value associated with the upper bounds
- Returns
The current dual value associated with the upper bound.
- ConstraintInstance.lslack()¶
Get the slack at lower bound body - lb.
- Returns
The slack at lower bound.
- ConstraintInstance.uslack()¶
Get the slack at upper bound ub - body
- Returns
The slack at upper bound.
- ConstraintInstance.slack()¶
Constraint slack (the lesser of lslack and uslack).
- Returns
The constraint slack.
- ConstraintInstance.sstatus()¶
Get the solver status (basis status of constraint’s slack or artificial variable)
- Returns
The solver status.
- ConstraintInstance.status()¶
Get the AMPL status if not in, otherwise solver status.
- Returns
The AMPL status.
- ConstraintInstance.setDual(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 to false (see
setOption
).- Parameters
dual (float) – The value to be assigned to the dual variable.
- ConstraintInstance.val()¶
Get the AMPL val suffix. Valid only for logical constraints.
- Returns
The val suffix.