University of Jyvaskyla, Scientific Visualization

Main help page | OVi Tutorial | Optimization Methods | Mathematical Expressions Visualization | The Ovi User Interface

OVi Guided Tour

In this section we show how to solve one example. This also illustrates the basic steps one must go through when using OVi. These steps are:

I Enter the objective function

The basic purpose of every optimization algorithm is to minimize the value of the objective function, i.e., to find the point (x₁, x₂, ..., x_n) where the function reaches its smallest value. The objective function is entered into the appropriate field in the main window (without the lefthand side of the function , i.e., the name of the function!):

For more information about the syntax and the operation of the input, you can see the section Mathematical Expressions.

II Choose the optimization methods to be used

In order to specify the desired optimization methods you must press either insert or edit buttons in the main window. OVi then launches a separate window called "Method chain", which looks like this:

The name of the combination should be entered into the first field on the top of the window. The name isn't compulsory, but it helps you to identify different solution processes.

The different levels of optimization (unimodal, line search, multi dimensional search and constrained) can be chosen by pressing one of the four push buttons on the top of the window (below the name field). After the selection of the level, the leftmost listbox reflects the methods in concern. To select (or unselect) a method in the list just press the left mouse button. If the selected method needs some special initial values, they will show up in the rightmost listbox. The chain of the optimization algorithms must be completely specified in order to be able to proceed. For more information about the optimization algorithms, see the section Optimization Methods.

The starting point and epsilon (final accuracy tolerance) must be entered into the two fields on the right.

When you are satisfied with the method combination, press done.

III View the optimization results

To carry out the actual optimization you must press 'Solve' in the main window. After this, you can view the optimization statistics (numerically) by selecting Results | Statistic... from the main window. This is what the "Statistics"-window looks like:

The optimization combinations specified by the user can be browsed by pressing the Previous and the Next buttons on the window. From the Results menu entry you can select which information on a single iteration to be shown in the Statistic window.

IV Viewing the graph

The visual window is launched by selecting Data | Graphical Display from the main window. In the example view the function is visualized by a graph. The red line shows the optimization path:

The objective function can be viewed in different ways and it can be rotated and translated by the mouse movements. For additional information about the Visual Window menus and viewing the graph see Visualization.

Good luck! The OVi team Samuli, Jani, Markku-Juhani and Kimmo.