Dakota Reference Manual: interval_type

| Dakota Reference Manual Version 6.15 Explore and Predict with Confidence

- Main Page
- Related Pages

All Pages
interval_type

Specify how to compute gradients and hessians

## Specification

Alias: none

Argument(s): none

Default: forward

## Description

The `interval_type` setting is used to select between `forward` and `central` differences in the numerical gradient calculations. The `dakota`, DOT `vendor`, and OPT++ `vendor` routines have both forward and central differences available, the CONMIN, NL2SOL and ROL `vendor` routines support forward differences only, and the NPSOL and NLSSOL `vendor` routines start with forward differences and automatically switch to central differences as the iteration progresses (the user has no control over this). The following forward difference expression

and the following central difference expression

are used to estimate the component of the gradient vector.