Dakota Reference Manual
Version 6.4
LargeScale Engineering Optimization and Uncertainty Analysis

Gradients are needed and will be obtained from a mix of numerical and analytic sources
Alias: none
Argument(s): none
Required/Optional  Description of Group  Dakota Keyword  Dakota Keyword Description  

Required  id_numerical_gradients  Identify which numerical gradient corresponds to which response  
Required  id_analytic_gradients  Identify which analytical gradient corresponds to which response  
Optional  method_source  Specify which finite difference routine is used  
Optional (Choose One)  Group 1  dakota  (Default) Use internal Dakota finite differences algorithm  
vendor  Use nonDakota fd algorithm  
Optional  interval_type  Specify how to compute gradients and hessians  
Optional (Choose One)  Group 2  forward  (Default) Use forward differences  
central  Use central differences  
Optional  fd_step_size  Step size used when computing gradients and Hessians 
The mixed_gradients
specification means that some gradient information is available directly from the simulation (analytic) whereas the rest will have to be finite differenced (numerical). This specification allows the user to make use of as much analytic gradient information as is available and then finite difference for the rest.
The method_source
, interval_type
, and fd_gradient_step_size
specifications pertain to those functions listed by the id_numerical_gradients
list.
For example, the objective function may be a simple analytic function of the design variables (e.g., weight) whereas the constraints are nonlinear implicit functions of complex analyses (e.g., maximum stress).
These keywords may also be of interest: