Managing data

Describes C++ classes to manage data.

Usually the data of an optimization problem must be collected before or during the creation of the Concert Technology representation of the model. Though, in principle, modeling does not depend on how the data is generated and represented, this task may be facilitated by the array classes or set classes, such asIloNumSet, provided by Concert Technology.

For example, objects of class IloNumArray can be used to store numeric data in arrays. Elements of the class IloNumArray can be accessed like elements of standard C++ arrays, but the class also offers a wealth of additional features. For example, Concert Technology arrays are extensible; in other words, they transparently adapt to the required size when new elements are added using the method add . Conversely, elements can be removed from anywhere in the array with the method remove . Concert Technology arrays also provide debugging support when compiled in debug mode by using assert statements to make sure that no element beyond the array bounds is accessed. Input and output operators (that is,  operator << and  operator >>) are provided for arrays. For example, the code:

IloNumArray data(env, 3, 1.0, 2.0, 3.0); 
cout << data << endl;

produces the following output:

[1.0, 2.0, 3.0]

When you have finished using an array and want to reclaim its memory, call the method end; for example, data.end. When the environment ends, all memory of arrays belonging to the same environment is returned to the system as well. Thus, in practice you do not need to call end on an array (or any other Concert Technology object) just before calling env.end.

The constructor for arrays specifies that an array of size 3 with elements 1.0, 2.0, and 3.0 is constructed. This output format can be read back in with, for example:

cin >> data;

The Example: optimizing the diet problem in C++ takes advantage of this function and reads the problem data from a file.

Finally, Concert Technology provides the template class IloArray<X> to create array classes for your own type X. This technique can be used to generate multidimensional arrays. All the functions mentioned here are supported for IloArray classes except for input/output, which depends on the input and output operator being defined for type X.