Dakota Reference Manual: energy

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energy

Truncate the subspace based on eigenvalue energy

## Specification

Alias: none

Argument(s): none

Child Keywords:

| Required/Optional | Description of Group | Dakota Keyword | Dakota Keyword Description
--- | --- | --- | --- | ---
| Optional | truncation_tolerance | Specify the maximum percentage (as a decimal) of the eigenvalue energy not captured by the active subspace representation.

## Description

Uses a criterion based on the derivative matrix eigenvalue energy.

Usage Tips

This subspace truncation method may work best when working with non-normally distributed uncertain variables. If this automated diagnostic does not yield desirable results, consider using the explicit dimension truncation option or one of the other truncation methods.

## Theory

Using the eigenvalue energy truncation metric, the subspace size is determined using the following equation:

where is the truncation_tolerance, is the estimated subspace size, is the size of the full space, and are the eigenvalues of the derivative matrix.