Configuring the Design Variables

You use the Design Variables tab to select the parameters that will be used as design variables in your model.

For the Pointer Automatic Optimizer technique, you can only define 200 design variables. The other techniques do not have a limit on the number of design variables that you can define.

  1. From the Optimization Component WebTop Editor, click the Design Variables tab.

  2. Perform the following actions, which may vary based on your model design:

    1. Determine which parameters you want to use as variables by selecting the corresponding check boxes in the first column. Alternatively, you can click Check All to add all the selected parameters (including array elements) as design variables. To clear all the parameters, click Check None.

      Selecting a subflow parameter as a variable will, at a later time, create a corresponding parameter in the Optimization component. Only real, integer, and string parameters can be variables.

    2. Specify the Lower Bound for the variables in the corresponding column. If you do not specify lower bound values, Isight uses the default value –1e15. This results in a large range for the design variables and may reduce the chances of finding a good design. It is recommended that you specify lower bounds for all variables. This setting is required if you are using the automatic scaling component preference.
    3. Specify the Upper Bound for the variables in the corresponding column. If you do not specify upper bound values, Isight uses the default value +1e15. This results in a large range for the design variables and may reduce the chances of finding a good design. It is recommended that you specify upper bounds for all variables. This setting is required if you are using the automatic scaling component preference.
    4. Type a list of allowed values in the Allowed Values column, separated by a semicolon. If you enter allowed values, the lower and upper bounds are erased and vice versa. Entering a list of allowed values creates a discrete variable and the Optimization component uses only these values during optimization. The optimization algorithm will view this variable as an integer parameter with the range of values 0, 1, 2, ..., N−1, where N is the length of the allowed values list.
    5. Set the Scale Factor for the variable in the corresponding column. Scale factors are used to bring variable values to the same order of magnitude to improve the efficiency of the optimizers.

      Note: This column does not appear if you use the automatic scaling component preference.

    6. (Multi-Island Genetic Algorithm technique only) Set the value in the Gene Size column. This value controls the number of bits N in all genes used for encoding the value of each variable. Every bit of the gene can change its value between 0 and 1. The total number of possible combinations in every gene is then 2N. This number of combinations determines the minimum change in the value of any design variable during all genetic operations—take the allowed range of values for a design variable and divide it by the total number of combinations. To increase the minimum change in design variable values (i.e., to decrease the number of possible bit combinations when the allowed range of design variable values is small), decrease the gene size.

  3. Click Update Component to save your changes