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In specific scenarios, system allows user to define what parameter values can never be tested together or in the other hand, scenarios where parameter values can only be tested together. 
For that, user can apply constraints to support these cases.

So that the model can understand the requirements, you have the option to define invalid constraints (values that can never be tested together), and/or bound constraints (values that can only be tested together) to train the model.

Invalid constraints

Invalid constraints restrict parameter values that can never be tested together.

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