Sandia National Laboratories

# active_set_vector

Deactivate the Active Set Vector

Specification

- Alias: None

- Arguments: None

Description

Allows the user to turn off any variability in ASV values so that active set logic can be omitted in the user’s simulation interface. This option trades some efficiency for simplicity in interface development.

The default behavior is to request the minimum amount of data required by an algorithm at any given time, which implies that the ASV values may vary from one function evaluation to the next. Since the user’s interface must return the data set requested by the ASV values, this interface must contain additional logic to account for any variations in ASV content.

Deactivating this ASV control causes Dakota to always request a “full” data set (the full function, gradient, and Hessian data that is available from the interface as specified in the responses specification) on each function evaluation.

For example, if ASV control has been deactivated and the responses section specifies four response functions, analytic gradients, and no Hessians, then the ASV on every function evaluation will be { 3 3 3 3 }, regardless of what subset of this data is currently needed. While wasteful of computations in many instances, this simplifies the interface and allows the user to return the same data set on every evaluation. Conversely, if ASV control is active (the default behavior), then the ASV requests in this example might vary from { 1 1 1 1 } to { 2 0 0 2 }, etc., according to the specific data needed on a particular function evaluation. This will require the user’s interface to read the ASV requests and perform the appropriate logic in conditionally returning only the data requested.

Usage Tips

- In general, the default ASV behavior is recommended for the sake of computational efficiency, unless interface development time is a critical concern.

- Whether active or inactive, the data returned to Dakota from the user’s interface must match the ASV passed in, or else a response recovery error will result. However, when the ASV control is deactivated, the ASV values are invariant and need not be checked on every evaluation.

- Deactivating the ASV control can have a positive effect on load balancing for parallel Dakota executions. Thus, there is significant overlap in this ASV control option with speculative gradients. There is also overlap with the mode override approach used with certain optimizers to combine individual value, gradient, and Hessian requests.

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