Class IloRange

This class models a constraint of the form:

 lowerBound <= expression <= upperBound
 

You can create a range from the constructors in this class or from the arithmetic operators on numeric variables (instances of IloNumVar and its subclasses) or on expressions (instances of IloExpr and its subclasses):

• operator <=
• operator >=
• operator ==

After you create a constraint, such as an instance of IloRange, you must explicitly add it to the model in order for it to be taken into account. To do so, use the member function IloModel::add to add the range to a model and the member function IloAlgorithm::extract to extract the model for an algorithm.

Most member functions in this class contain assert statements. For an explanation of the macro NDEBUG (a way to turn on or turn off these assert statements), see the concept Assert and NDEBUG.

What Is Extracted

All the variables (that is, instances of IloNumVar or one of its subclasses) in the range (an instance of IloRange) will be extracted when an algorithm such as IloCplex, documented in the CPLEX C++ API Reference Manual, extracts the range.

Normalizing Linear Expressions: Reducing the Terms

Normalizing is sometimes known as reducing the terms of a linear expression.

Linear expressions consist of terms made up of constants and variables related by arithmetic operations; for example, x + 3y. In some linear expressions, a given variable may appear in more than one term, for example, x + 3y +2x. Concert Technology has more than one way of dealing with linear expressions in this respect, and you control which way Concert Technology treats linear expressions from your application.

In one mode (the default mode), Concert Technology analyzes linear expressions that your application passes it, and attempts to reduce them so that a given variable appears in only one term in the expression. You set this mode with the member function IloEnv::setNormalizer(IloTrue) .

Certain constructors and member functions in this class check this setting in the model and behave accordingly: they attempt to reduce expressions. This mode may require more time during preliminary computation, but it avoids the possibility of an assertion in some of the member functions of this class failing in the case of duplicates.

In the other mode, Concert Technology assumes that no variable appears in more than one term in any of the linear expressions that your application passes to Concert Technology. We call this mode assume normalized linear expressions. You set this mode with the member function IloEnv::setNormalizer(IloFalse).

Certain constructors and member functions in this class check this setting in the model and behave accordingly: they assume that no variable appears in more than one term in an expression. This mode may save time during computation, but it entails the risk that an expression may contain one or more variables, each of which appears in one or more terms. This situation will cause certain assert statements in Concert Technology to fail if you do not compile with the flag -DNDEBUG.

This constructor creates an empty range constraint. Before you use this constraint, you must fill the range. The optional argument name is set to 0 by default.

After you create a range constraint, you must explicitly add it to a model in order for it to be taken into account. To do so, use the member function IloModel::add.

This constructor creates a range constraint from an expression (an instance of the class IloNumExprArg) and its upper bound (rhs). The default bound for rhs is the symbolic constant IloInfinity. The optional argument name is set to 0 by default.

This constructor creates a range constraint from an expression (an instance of the class IloNumExprArg) and its upper bound (rhs). Its lower bound (lhs) will be -IloInfinity. The default bound for rhs is IloInfinity. The optional argument name is set to 0 by default.

This member function returns the expression of the invoking IloRange object.

This member function returns the lower bound of the invoking range.

This member function creates and returns an iterator to traverse linear expressions in the invoking range.

This member function creates and returns an iterator to traverse quadratic expressions in the invoking range.

This member function returns the upper bound of the invoking range.

This operator creates the objects needed internally to represent a range in column-wise modeling. See the concept Column-Wise Modeling in CPLEX for an explanation of how to use this operator in column-wise modeling.

This member function sets lb as the lower bound and ub as the upper bound of the invoking range, and it creates the appropriate instance of the undocumented class IloChange to notify algorithms about this change of an extractable object in the model.

This member function sets expr as the invoking range, and it creates the appropriate instance of the undocumented class IloChange to notify algorithms about this change of an extractable object in the model.

This member function sets lb as the lower bound of the invoking range, and it creates the appropriate instance of the undocumented class IloChange to notify algorithms about this change of an extractable object in the model.

This member function sets value as the linear coefficient of the variable var in the invoking range, and it creates the appropriate instance of the undocumented class IloChange to notify algorithms about this change of an extractable object in the model.

If you attempt to use setLinearCoef on a non linear expression, it will throw an exception on platforms that support C++ exceptions when exceptions are enabled.

For each of the variables in vars, this member function sets the corresponding value of values (whether integer or floating-point) as its linear coefficient in the invoking range, and it creates the appropriate instance of the undocumented class IloChange to notify algorithms about this change of an extractable object in the model.

If you attempt to use setLinearCoef on a non linear expression, it will throw an exception on platforms that support C++ exceptions when exceptions are enabled.

This member function sets ub as the upper bound of the invoking range, and it creates the appropriate instance of the undocumented class IloChange to notify algorithms about this change of an extractable object in the model.