Nonprocedural Execution

Execution based on definitions

Execution based on definitions is typically not controlled by the user. It takes place automatically, but only when up-to-date values of defined sets or parameters are needed. Basically, execution can be triggered automatically from within:

  • the body of a function or procedure, or

  • an object in the graphical user interface.

Relating definitions and procedures

Consider a set or a parameter with a definition which is referenced in an execution statement inside a function or a procedure. Whenever the value of such a set or parameter is not up-to-date due to previous data changes, AIMMS will compute its current value just prior to executing the corresponding statement. This mechanism ensures that, during execution of functions or procedures, the functional relationships expressed in the definitions are always valid.

Lazy evaluation

During execution AIMMS minimizes its efforts and updates only those values of defined identifiers that are needed at the current point of execution. Such lazy evaluation can avoid unnecessary computations and reduces computational time significantly when the number of dependencies is large, and when relatively few dependencies need to be resolved at any particular point in time.

GUI requests

For the graphical objects in an end-user interface you may specify whether the data in that object must be up-to-date at all times, or just when the page containing the object is opened. AIMMS will react accordingly, and automatically update all corresponding identifiers as specified.

The set CurrentAutoUpdatedDefinitions

Which definitions are automatically updated in the graphical user interface whenever they are out-of-date, is determined by the contents of the predefined set CurrentAutoUpdatedDefinitions. This set is a subset of the predefined set AllIdentifiers, and is initialized by AIMMS to the union of the sets AllDefinedSets and AllDefinedParameters by default.

Exclude from auto-updating

To prevent auto-updating of particular identifiers in your model, you should remove such identifiers from the set CurrentAutoUpdatedDefinitions. You can change its contents either from within the language or from within the graphical user interface. Typically, you should exclude those identifiers from auto-updating whose computation takes a long time to finish. Instead of waiting for their computation on every input change, it makes much more sense to collect all input changes for such identifiers and request their re-computation on demand.

Requesting updates

All identifiers that are not contained in CurrentAutoUpdatedDefinitions must be updated manually under your control. AIMMS provides several mechanisms:

  • you can call the UPDATE statement from within the language, or

  • you can attach update requests of particular identifiers as actions to buttons and pages in the end-user interface.

The UPDATE statement

The UPDATE statement can be used to update the contents of one or more identifiers during the execution of a procedure that is called by the user. In this way, selected identifiers which are shown in the graphical user interface and not kept up-to-date automatically, can be made up-to-date once the procedure is activated by the user.



image/svg+xmlUPDATE identifier , ;

Allowed identifiers

The following selections of identifiers are allowed in the UPDATE statement:

  • identifiers with a definition,

  • identifiers associated with a structural section in the model-tree, and

  • identifiers in a subset of the predefined set AllIdentifiers.


The following execution statement inside a procedure will trigger AIMMS to update the values of the identifiers FixedCost, VariableCost and TotalCost upon execution.

Update FixedCost, VariableCost, TotalCost;