Building the Model

Starting a new project

Getting AIMMS

All current versions of AIMMS are provided as an installation free software. Instead of creating a directory in the Program Files and a dedicated launch icon, an execution file for the AIMMS versions that you have downloaded and run is stored in your local user directory. You can download the latest version of AIMMS from the download section on our website

The AIMMS Launcher

The AIMMS Launcher is a useful tool which enables you to easily run, manage, and navigate through all of the AIMMS versions on your computer. The AIMMS Launcher automatically creates a launch icon on your desktop to easily access and launch any version of AIMMS that you have available on your computer. The AIMMS Launcher is also available on the download section of our website.

Starting AIMMS

To run AIMMS you simply double click on the AIMMS Launcher icon on your desktop and select the preferred AIMMS version to run from the list and press the Launch button. Next, you will see the AIMMS splash screen. Once AIMMS has started, the splash screen will disappear and the AIMMS window will open.

Creating a new project from within AIMMS

Press the New Project button , which is located in the leftmost position on the AIMMS toolbar. The dialog box shown in Fig. 2 will then appear, requiring you to take the following actions:

• specify Beer Transport as the project name, and

• press the wizard button to select the folder for your AIMMS projects if the default folder .../Documents/AIMMS Projects/Beer Transport is not desired,

• change Default UI from ‘WebUI’ to ‘WinUI’. Uncheck the options ‘Include WebUI Library’ and ‘Include Pro Library’, and

• press the OK button.

Fig. 2 The New Project wizard

Next, the AIMMS Model Explorer and the AIMMS Page Manager will be automatically opened. We will look at the AIMMS Model Explorer first.

The Model Explorer

Initial model tree

When opened for the first time, the AIMMS Model Explorer will display the initial model tree shown in Fig. 3. In this initial model tree you will see

• a single declaration section where you can store the declarations used in your model,

• the predefined procedure MainInitialization, which is not relevant for this tutorial,

• the predefined procedure MainExecution, where you will put the execution statement necessary to solve the mathematical program, and

• the predefined procedure MainTermination, which is again not relevant for this tutorial.

Fig. 3 The initial model tree

See also

For more information on MainInitialization and MainExecution predefined procedures, you may investigate Model Initialization and Termination

Entering sets and indices

Opening the declaration section

The declaration of model identifiers requires you to first open the declaration section. You can do this either by clicking the icon or by double-clicking on the scroll icon . Note that double-clicking on the name of the declaration section instead of on its icon will open the attribute form of the declaration section and will therefore, at this point, not lead to the desired result. After opening the declaration section the standard identifier buttons on the toolbar will be enabled.

Creating the set Plants

To create a set of plants you should take the following actions:

• press the Set button to create a new set identifier in the model tree,

• specify Plants as the name of the set, and

• press the Enter key to register the name.

Opening its attribute form

Next, you need to declare the index \(p\) as an attribute of the set Plants. You can open the attribute form by double-clicking on the node Plants in the model tree. The resulting initial attribute form of the set Plants is shown in Fig. 4.

Fig. 4 The initial attribute form of the set Plants

Declaring the index \(p\)

To declare the index \(p\) as an attribute of the set Plants, execute the following sequence of actions:

• move the mouse cursor to the Index attribute field, and click in the (empty) edit field,

• enter the letter p, and

• complete the attribute form by pressing the Check, Commit and Close button .

Creating the set Customers

Next, create the set Customers with associated index \(c\) in exactly the same way as you created the set ‘Plants’ with index domain \(p\). Fig. 5 contains the resulting model tree.

Fig. 5 An intermediate model tree

Saving your changes

The asterisk on the left of the project name indicates that additions to your project have not yet been saved to disk. To save your work, please press the Save Project button on the toolbar.

Entering parameters and variables

Domain specification

In this section you will declare the parameters and variables that are needed in your model. The sets Plants and Customers and their associated indices will be used to specify the index domain for the parameters and variables.

Creating the parameter Supply

The declaration of a parameter is similar to the declaration of a set. To enter the parameter Supply(p), you should execute the following actions:

• press the parameter button on the toolbar to create a new parameter in the model tree,

• specify Supply(p) as the name of the parameter, and

• press the Enter key to register the name.

Note that parentheses are used to add the index domain \(p\) to the identifier Supply.

Creating the parameter Demand

The parameter ‘Demand(c)’ can be added in the same way. Should you make a mistake in entering the information, then you can always re-edit a name field by a single mouse click within the field.

Creating the parameter UnitTransportCost

The last model parameter UnitTransportCost is a two-dimensional parameter with index domain \((p,c)\). After entering UnitTransportCost(p,c), the resulting model tree should be the same as in Fig. 6.

Fig. 6 An intermediate model tree

Creating the variable Transport

Declaring a variable is similar to declaring a parameter.

• press the variable button on the toolbar to create a new variable in the model tree,

• specify Transport(p,c) as the name of the variable, and

• press the Enter key to register the variable.

Specifying range attribute

After opening the attribute form of the variable by double-clicking on the node Transport in the model tree, press the wizard button in front of the Range attribute field. The resulting dialog box provides the opportunity to specify the range of values that the variable Transport is allowed to take. In this case, select the Standard Range, then select nonnegative, and finally press the OK button (see Fig. 7).

Fig. 7 The AIMMS range wizard

Creating the variable TotalTransportCost

It should be clear by now how to create the variable TotalTransportCost. This variable will be used to specify the objective function. After entering its name, open the attribute form. There is no need to specify the range attribute, since the default range free will suffice. You are now ready to enter the following definition of this particular variable:

sum[ (p,c), UnitTransportCost(p,c) * Transport(p,c) ]

Specifying definition attribute

Simply enter the above definition in the Definition attribute field. You could type the entire sentence yourself, but you can also let AIMMS do some of the typing for you. Considering the parameter UnitTransportCost(p,c), the following two support features are quite useful.

• Type the letter u or U, and press the Ctrl + Spacebar combination for automatic name completion.

• Another option available to you is to drag the name UnitTransportCost(p,c) from the model tree to the edit field of the Definition attribute.

The attribute form should now have the same content as shown in Fig. 8. By pressing the Check, Commit and Close button , you can verify whether AIMMS will accept the definition you entered.

Fig. 8 The completed attribute form for the variable TotalTransportCost

Entering constraints and the mathematical program

The supply and demand constraints

Creating the supply and demand constraints, each with their own definition, requires the same actions as creating a variable with a definition (as you just completed). The only difference is that you must use the button instead of the button. The following two forms should be the result of your efforts.

Fig. 9 The completed attribute form for the constraint SupplyRestriction

Fig. 10 The completed attribute form for the constraint DemandRequirement

Creating the mathematical program

A mathematical program, unlike sets, parameters, variables and constraints, does not have a special button on the toolbar. By using the identifier button , you obtain access to all the other types of AIMMS identifiers. After pressing this button, select the Mathematical Program entry alongside the icon, press the OK button, and enter LeastCostTransportPlan as the name of the mathematical program.

Specifying its attributes

The complete the attribute form of the mathematical program as illustrated in Fig. 11. Among the attributes, AIMMS has automatically filled Direction, Constraints, Variables and Type attributes with default values and there is no need to change them for this project. You only need to fill the Objective attribute.

Fig. 11 The completed attribute form of the mathematical program

Selecting the objective

The Objective attribute wizard requires you to select a scalar variable. In the identifier selection wizard (see Fig. 12), simply select the scalar variable TotalTransportCost, and press the Finish button.

Fig. 12 The identifier selection wizard

Viewing the identifiers

Checking your model

You have now entered and declared all model identifiers. The resulting model tree is shown in Fig. 13. By pressing the F5 key you can instantly check the validity of your model. You will only receive a message in the event of an error. Once the validity of your model has been verified, you should save your work by pressing the Save Project button .

Fig. 13 The final model tree

Even though the Model Explorer is a convenient medium with which to build and inspect your model, AIMMS provides two other ways to view your model.

View text model

If you would like to see a text representation of the model, you can do the following:

• select node(s) in AIMMS Model Explorer,

• go to the View - Text Representation menu and execute the Selected Part(s) command (see Fig. 14).

Fig. 14 View text model

The text model provides a simple overview of selected identifiers. For instance, Fig. 15 shows the text model when the root node Main Beer Transport is selected.

Fig. 15 text model

Identifier overviews

Another way to inspect the model is by AIMMS Identifier Selector. This allows you to view several identifiers with similar properties at the same time. In this tutorial you will encounter one such example of a predefined view, namely all identifiers with a definition (see Fig. 16). AIMMS allows you to make your own views as you desire.

Fig. 16 View window with identifier definitions

Creating a view

You can create a view window by executing the following steps:

• press the Identifier Selector button on the toolbar,

• select the Identifiers with Definition node, and

• use the right mouse and select the Open With… command from the pop up menu (see Fig. 17).

Fig. 17 Identifier Selector window

For the selected identifiers the view can be constructed as follows:

• select the Domain - Definition entry from the View Manager window (see Fig. 18), and

• press the Open button to obtain the overall view.

Fig. 18 The View Manager window