radial_basis

Radial basis function (RBF) model

Specification

  • Alias: None

  • Arguments: None

Child Keywords:

Required/Optional

Description of Group

Dakota Keyword

Dakota Keyword Description

Optional

bases

Initial number of radial basis functions

Optional

max_pts

Maximum number of RBF CVT points

Optional

min_partition

(Inactive) Minimum RBF partition

Optional

max_subsets

Number of trial RBF subsets

Optional

export_model

Exports surrogate model in user-specified format(s)

Optional

import_model

Import surrogate model from archive file

Description

Radial basis functions \(\phi\) are functions whose value typically depends on the distance from a center point, called the centroid, \({\bf c}\) .

The surrogate model approximation comprises a sum of K weighted radial basis functions:

\[\hat{f}({\bf x})=\sum_{k=1}^{K}w_{k}\phi({\parallel {\bf x} - {\bf c_{k}} \parallel})\]

These basis functions take many forms, but Gaussian kernels or splines are most common. The Dakota implementation uses a Gaussian radial basis function. The weights are determined via a linear least squares solution approach. See [Orr96] for more details.

Known Issue: When using discrete variables, there have been sometimes significant differences in surrogate behavior observed across computing platforms in some cases. The cause has not yet been fully diagnosed and is currently under investigation. In addition, guidance on appropriate construction and use of surrogates with discrete variables is under development. In the meantime, users should therefore be aware that there is a risk of inaccurate results when using surrogates with discrete variables.