model

Specifies how variables are mapped into a set of responses

Topics

block

Specification

• Alias: None

• Arguments: None

Child Keywords:

Required/Optional	Description of Group	Dakota Keyword	Dakota Keyword Description
Optional		id_model	Give the model block an identifying name, in case of multiple model blocks
Required (Choose One)	Model Type	single	A model with one of each block: variable, interface, and response
		surrogate	An empirical model that is created from data or the results of a submodel
		nested	A model whose responses are computed through the use of a sub-iterator
		active_subspace	Active (variable) subspace model
		adapted_basis	Basis adaptation model
		random_field	Experimental capability to generate a random field representation. from data, from simulation runs, or from a covariance matrix. The representation may then be sampled for use as a random field input to another simulation. THIS IS AN EXPERIMENTAL CAPABILITY.
Optional		variables_pointer	Specify which variables block will be included with this model block
Optional		responses_pointer	Specify which reponses block will be used by this model block
Optional		hierarchical_tagging	Enables hierarchical evaluation tagging

Description

A model is comprised of a mapping from variables, through an interface, to responses.

Model Group 1 The type of model can be:

• single (default)

• surrogate

• nested

• subspace

• random_field

The input file must specify one of these types. If the type is not specified, Dakota will assume a single model.

Block Pointers and ID

Each of these model types supports variables_pointer and responses_pointer strings for identifying the variables and responses specifications used in constructing the model by cross-referencing with id_variables and id_responses strings from particular variables and responses keyword specifications.

These pointers are valid for each model type since each model contains a set of variables that is mapped into a set of responses – only the specifics of the mapping differ.

Additional pointers are used for each model type for constructing the components of the variable to response mapping. As an environment specification identifies a top-level method and a method specification identifies a model, a model specification identifies variables, responses, and (for some types) interface specifications. This top-down flow specifies all of the object interrelationships.

Examples

The first example shows a minimal specification for a single model, which is the default model when no models are explicitly specified by the user.

model
  single

The next example displays a surrogate model specification which selects a quadratic polynomial from among the global approximation methods. It uses a pointer to a design of experiments method for generating the data needed for building the global approximation, reuses any old data available for the current approximation region, and employs the first-order multiplicative approach to correcting the approximation each time correction is requested.

model,
  id_model = 'M1'
  variables_pointer = 'V1'
  responses_pointer = 'R1'
  surrogate
    global
      polynomial quadratic
      dace_method_pointer = 'DACE'
      reuse_samples region
      correction multiplicative first_order

This example demonstrates the use of identifiers and pointers. It provides the optional model independent specifications for model identifier, variables pointer, and responses pointer as well as model dependent specifications for global surrogates (see global).

Finally, an advanced nested model example would be

model
  id_model = 'M1'
  variables_pointer = 'V1'
  responses_pointer = 'R1'
  nested
    optional_interface_pointer = 'OI1'
      optional_interface_responses_pointer = 'OIR1'
     sub_method_pointer = 'SM1'
       primary_variable_mapping  = '' '' 'X'   'Y'
       secondary_variable_mapping = '' '' 'mean' 'mean'
       primary_response_mapping  = 1. 0. 0. 0. 0. 0. 0. 0. 0.
       secondary_response_mapping = 0. 0. 0. 1. 3. 0. 0. 0. 0.
                                    0. 0. 0. 0. 0. 0. 1. 3. 0.

This example illustrates controls for model identifier, variables pointer, and responses pointer and for specifying details of the nested mapping.