Fit Methods

Numerical methods available for a Fit approach.

Method Response Characteristics Accuracy Efficiency Basic Parameters Comments
Fit Automatically Selected by Training General N/A N/A Choose methods for Fit Automatically Selected by Training to consider. Selects the most appropriate method and settings.

It it recommended that you use this method unless you desire a specific method and settings.
HyperKriging Interpolated data ✩✩✩ ✩✩ The time to build the Fit and use the Fit (Evaluate From) increases with both the number of runs and the number of design variables in the input matrix.

The number of design variables has more influence than the number of runs if order is larger than 1.
Least Squares Regression Data trend lines ✩ ✩✩✩ Noises can be screened out with this method.

Closed form equations are available.
Moving Least Squares Method (MLSM) General ✩✩ ✩✩ The time to build the Fit and use the Fit (Evaluate From) increases with both the number of runs and the number of design variables in the input matrix.

The number of design variables has more influence than the number of runs if order is larger than one.
Radial Basis Function Interpolate data ✩✩✩ ✩✩ The time to build the Fit increases with both the number of runs and the number of design variables in the input matrix.

The number of runs has more influence than the number of design variables.

The run time for using the Fit in another approach (Evaluate From) is very small regardless of the size of the input matrix.
romAI Leverages multilayer perceptron (MLP) and classical system theory
Altair romAI requires installation of Twin Activate (version 2023.1 and above) and romAI block to be activated in the extensions:
  • Set HW_HST_TWINACTIVATE env and point to the TwinActivate.bat file (i.e., C:\Program Files\Altair\2023.1\TwinActivate2023.1\TwinActivate.bat)
  • Enable romAI Director from extensions in Twin Activate.
    Note: romAI model is not active by default. Please go to preferences_study.mvw under “<install directory>/hw/prefinc/” and activate it by adding an asterisk before its registration line under *BeginExternalFitDefaults statement.
*BeginExternalFitDefaults()
        *RegisterExternalFit(RomAI, "RomAI",    
          {getenv("ALTAIR_HOME") + "/hst/etc/fit/rom_ai/romAI.py"})