Configuring the Sobol Sequence Technique

You can configure the Sobol Sequence technique options.

  1. Double-click the DOE component .
    The DOE Component Editor appears.
  2. From the DOE Technique list on the General tab, select Sobol Sequence.
  3. In the DOE Technique Options area, enter the Total number of points that you want to study.
  4. Of which, number of corner points is the number of corner points you want.
    Notes:
    • Although you can provide any positive integer value as number of corner points, the maximum number of corner points (m) that can be generated are 2 ( n - 1 ) for even number of factors, and 2 ( n - 1 ) + 1 for odd number of factors, where n is number of factors. The actual number of corner points generated maybe reduced further if they don’t satisfy Constraint Expression as discussed below.
    • Inclusion of more than 2 corner points is supported only for up to 17 factors. For 18 or more factors, a maximum of 2 corner points can be included - one representing lower bound values for all factors, and another representing upper bound values for all factors.
  5. Select the Include baseline point checkbox to include baseline point in design matrix even if it is neither a Sobol Sequence point nor a corner point.
  6. For each point other than baseline and corner points, Sobol Sequence point (a number on the unit interval) is applied to the design space for each factor.
  7. Enter the Number of initial Sobol points to be skipped value to control the starting value from the Sobol Sequence to be used for the design points.

    The default value of 0 indicates that no initial values in the Sobol Sequence are skipped.

  8. Click on Factors tab, select desired parameters.
    Click on Constraint... if you wish to apply constraint on factors. This opens a Constraint Expression dialogue box where you can specify the constraint expression you wish to impose on factors.
    Notes:
    • The expression must be a Boolean expression i.e. the evaluated expression must always return a Boolean value.
    • The dialogue box will not close unless it has valid expression which evaluates to a Boolean value
    • Since the constraint is to be defined by an end user, it may happen that the defined constraint is too restrictive, or even impossible to be fulfilled. In such a scenario, the search for valid design points may go on for too long duration, or may not end at all. To avoid the possibility of too long or indefinite search for valid points, a timeout field Max time to find compliant points (seconds): is added in the dialogue with default value as 60 seconds. The timeout must be a non-zero and positive integer value.
    • If timeout is reached before expected number of points are generated, the technique will stop searching for new points and return all the valid points generated till the timeout expires.
    • The filter option available on Design Matrix tab is no more available for Sobol Sequence technique. If a filter expression has been defined for Sobol Sequence technique in models authored using Isight 2021, the filter expression shall be ignored when such model is executed using Isight 2024 or later.
  9. Click OK to save your changes and to close the DOE Component Editor.