Blurb::
Surrogate is used in lieu of true model for mesh adaptive search

Description::
When \c optimize is specified with \c use_surrogate, \c
mesh_adaptive_search will use the surrogate in lieu of the true model
and thus the true function is never invoked except to construct the
surrogate.

<b> Default Behavior </b>

\c optimize is the default surrogate usage mode.

<b> Expected Output </b>

The user can expect to see both the number of true model evaluations
and the number of approximation (i.e., surrogate) evaluations reported
in the Dakota screen output.  The former should equal the number of
truth evaluations done for the surrogate construction.

Examples::

The following example shows the syntax used to set \c
use_surrogate to \c optimize.

\verbatim
method,
	mesh_adaptive_search
	model_pointer = 'SURROGATE'
	use_surrogate optimize

model,
	id_model = 'SURROGATE'
	surrogate global
	polynomial quadratic
	dace_method_pointer = 'SAMPLING'

variables,
	continuous_design = 3
	  initial_point   -1.0    1.5   2.0
	  upper_bounds    10.0   10.0  10.0
	  lower_bounds   -10.0  -10.0 -10.0
	  descriptors      'x1'  'x2'  'x3'
	discrete_design_range = 2
	  initial_point      2     2
	  lower_bounds       1     1
	  upper_bounds       4     9
	  descriptors      'y1'   'y2'
       discrete_design_set
         real = 2
           elements_per_variable = 4 5
           elements = 1.2 2.3 3.4 4.5 1.2 3.3 4.4 5.5 7.7
           descriptors      'y3'   'y4'
         integer = 2
           elements_per_variable = 2 2
           elements = 4 7 8 9
           descriptors      'z1'   'z2'

method,
	id_method = 'SAMPLING'
	model_pointer = 'TRUTH'
	sampling
	  samples = 55

model,
	id_model = 'TRUTH'
	single
	  interface_pointer = 'TRUE_FN'

interface,
	id_interface = 'TRUE_FN'
       direct
	  analysis_driver = 'text_book'

responses,
	objective_functions = 1
	no_gradients
	no_hessians
\endverbatim

The following will appear toward the end of the screen output when
Dakota is run on this example.  The number of true function
evaluations includes only the 55 evaluations that were done to
construct the surrogate (as specified in the SAMPLING method block).

\verbatim
<<<<< Function evaluation summary (APPROX_INTERFACE): 221 total (221 new, 0 duplicate)
<<<<< Function evaluation summary (TRUE_FN): 55 total (55 new, 0 duplicate)
\endverbatim

Theory::
Faq::
See_Also::
