Working with the Set AllIdentifiers

Working with AllIdentifiers

Throughout your model you can use the predefined set AllIdentifiers to construct and work with dynamic collections of identifiers in your model. Several operators in AIMMS support the use of a subset of AllIdentifiers instead of an explicit list of identifier names, while other operators support the use of an index into AllIdentifiers instead of a single explicit identifier name.

Constructing identifier sets

AIMMS offers a number of constructs that can help you to construct a meaningful subset of AllIdentifiers. They are:

• set algebra with other predefined identifier subsets, and

• dynamic selection based on model query functions.

Predefined identifier sets

When compiling your model, AIMMS automatically creates an identifier set for every section in your model. Each such set contains all the identifier names that are declared in the corresponding section. In addition, for every identifier type, AIMMS fills a predeclared set AllIdentifierTypes (e.g. AllParameters, AllSets) with all the identifiers of that type. The complete list of identifier type related sets defined by AIMMS can be found in Function Reference. You can use both type of sets to perform set algebra to construct particular identifier subsets of interest to your model.

Example

If your model contains a section Unit Model, you can assign the collection of all parameters in that section to a subset UnitModelParameters of AllIdentifiers through the assignment

UnitModelParameters := Unit_Model * AllParameters;

Model query functions

Another method to construct meaningful subsets of AllIdentifiers consists of using the functions provided to query aspects of those identifiers. Selected examples are:

• the function IdentifierDimension returning the dimension of the identifier,

• the function IdentifierType returning the type of the identifier as an element of AllIdentifierTypes,

• the function IdentifierText returning the contents of the TEXT attribute, and

• the function IdentifierUnit returning the contents of the UNIT attribute.

These functions take as argument an element in the set AllIdentifiers.

Functions accepting identifier index

In addition to the functions lists above, the functions Card and ActiveCard also accept an index into the set AllIdentifiers. They will then return the cardinality of the identifier represented by the index, or the cardinality of the active elements of that identifier, respectively. You can also use these functions to dynamically construct a subset of AllIdentifiers.

Example

The set expression

{ IndexIdentifiers in UnitModelParameters |
        IdentifierDimension( IndexIdentifier ) = 3 }

refers to the collection of all 3-dimensional parameter in the section Unit Model.

Working with identifier sets

The following operators in AIMMS support identifier subsets to represent a collection of individual identifiers:

• the READ and WRITE operators,

• the EMPTY, CLEANUP, CLEANDEPENDENTS, and REBUILD operators.

If you are interested in the contents of an identifier subset, you can use the DISPLAY operator, which will just print the identifier names contained in the set, rather than the contents of the identifiers referred to in the identifier set as is the case for the WRITE statement.

Functions accepting identifier sets

In addition to the operators above, the following AIMMS functions also operate on subsets of AllIdentifiers:

• GenerateXML,

• CaseCompareIdentifier,

• CaseCreateDifferenceFile,

• IdentifierMemory,

• GMP::Solution::SendToModelSelection,

• VariableConstraints,

• ConstraintVariables,

• ScalarValue,

• SectionIdentifiers,

• AttributeToString,

• IdentifierAttributes.

See also Model Query Functions of the AIMMS Function Reference.