Dakota Reference Manual
Version 6.2
LargeScale Engineering Optimization and Uncertainty Analysis

Select the built in Gaussian Process surrogate
Alias: none
Argument(s): none
Required/Optional  Description of Group  Dakota Keyword  Dakota Keyword Description  

Optional  point_selection  Enable greedy selection of wellspaced build points  
Optional  trend  Choose a trend function for a Gaussian process surrogate 
A second version of GP surrogates was available in prior versions of Dakota. For now, both versions are supported but the dakota
version is deprecated and intended to be removed in a future release.
Historically these models were drastically different, but in Dakota 5.1, they became quite similar. They now differ in that the Surfpack GP has a richer set of features/options and tends to be more accurate than the Dakota version. Due to how the Surfpack GP handles illconditioned correlation matrices (which significantly contributes to its greater accuracy), the Surfpack
GP can be a factor of two or three slower than Dakota's. As of Dakota 5.2, the Surfpack implementation is the default in all contexts except Bayesian calibration.
More details on the gaussian_process
dakota model can be found in[58].
Dakota's GP deals with illconditioning in two ways. First, when it encounters a noninvertible correlation matrix it iteratively increases the size of a "nugget," but in such cases the resulting approximation smooths rather than interpolates the data. Second, it has a point_selection
option (default off) that uses a greedy algorithm to select a wellspaced subset of points prior to the construction of the GP. In this case, the GP will only interpolate the selected subset. Typically, one should not need point selection in trustregion methods because a small number of points are used to develop a surrogate within each trust region. Point selection is most beneficial when constructing with a large number of points, typically more than order one hundred, though this depends on the number of variables and spacing of the sample points.
This differs from the point_selection
option of the Dakota GP which initially chooses a wellspaced subset of points and finds the correlation parameters that are most likely for that one subset.