Use the Sensitivity (
) study step to add a sensitivity analysis to the study. Using a Sensitivity study node, you can add sensitivity functions at the study level and use model parameters as global control variables. Compared to
The Sensitivity Interface, the Sensitivity study step has these capabilities:
The Settings window has the following sections:
Choose a method from the Gradient method list: one of the analytical methods
Forward or
Adjoint (the default). See
Choosing a Sensitivity Method for information about the forward and adjoint methods. These methods have similar limitations as the gradient-based optimization methods (SNOPT and Levenberg-Marquardt). For example, nonanalytic functions are not correctly treated. Also, when model parameters are used in the geometry or mesh, the sensitivity is not correctly computed.
You choose the study step to use from the Study step list, which contains
None and any supported study steps in the study. The supported study step types are Stationary, Time Dependent, and Frequency Domain.
You specify the objective function for the optimization problem in the table’s Expression column. Enter any globally available expression that evaluates to a real number. Optionally, you can add a description in the
Description column. Click the
Add Expression (
) and
Replace Expression (
) buttons to search through a list of predefined expressions.
Here you select the evaluation method of the objective function when several solutions are present, like for Time Dependent studies. For sensitivity studies, only Auto is available. The solver chooses the evaluation method based on the innermost study. For studies in the
Frequency Domain, the contributions from all solutions are summed (equivalent to the
Sum of objectives option). For a
Time Dependent study, the optimization solver selects the last solution (final time).
The table under Control Variables and Parameters is used to define control variables. In this table you can select all parameters defined in the
Global Definitions>Parameters node’s
Settings window through the
Add (
) button.
From a list in the Parameter name column, select the parameter to define as a control variable. You can then give it a value and scale as a control variable in the
Value and
Scale columns, respectively. If the control value is complex-valued, select
Complex from the list in the
Value type column (the default is
Real).
Move control parameter rows up and down using the Move Up (
) and
Move Down (
) buttons. To remove a control parameter, select some part of that parameter’s row in the table and click the
Delete button (
).
You can also save the definitions of the control parameters to a text file by clicking the Save to File button (
) and using the
Save to File dialog box that appears. To load a text file with control variables, click the
Load from File button (
) and use the
Load from File dialog box that appears. Data must be separated by spaces or tabs.