Blurb::
Specifies how function evaluations will be performed in order to map
the variables into the responses.

Description::
The interface section in a Dakota input file specifies how function
evaluations will be performed in order to map the variables into the
responses.  The term "interface" refers to the bridge between Dakota
and the underlying simulation code.

In this context, a "function evaluation" is the series of operations
that takes the variables and computes the responses. This can be
comprised of one or many codes, scripts, and glue, which are
generically referred to as "analysis drivers" (and optional
input/output filters).  The mapping actions of \ref
interface-analysis_drivers may be combined with explicit \ref
interface-algebraic_mappings

<b>Parallelism Options</b>

\li The \ref interface-asynchronous keyword enables concurrent local
    function evaluations or analyses via operating system process
    management.  Its child keywords allow tailoring the evaluation and
    analysis concurency.

\li The evaluation servers, scheduling mode (master, peer static or
    dynamic), and processor keywords allow a user to override Dakota's
    default evaluation configuration when running in parallel (MPI)
    mode.

\li The analysis servers and scheduling mode (master, peer static or
    dynamic) keywords allow a user to override Dakota's default
    analysis configuration when running in parallel (MPI) mode.

Note: see \ref interface-analysis_drivers-direct for the specific \c
processors_per_analysis specification supported for direct
interfaces.

The ParallelLibrary class and the Parallel Computing chapter of the
Users Manual \cite UsersMan provide additional details on parallel
configurations.

Topics::	block
Examples::
Theory::
Function evaluations are performed using either interfaces to
simulation codes, algebraic mappings, or a combination of the two.

When employing mappings with simulation codes, the interface invokes
the simulation using either forks, direct function invocations, or
computational grid invocations.

- In the fork case, Dakota will treat the simulation as a black-box
  and communication between Dakota and the simulation occurs through
  parameter and result files. This is the most common case.

- In the direct function case, the simulation is internal to Dakota
  and communication occurs through the function parameter list. The
  direct case can involve linked simulation codes or test functions
  which are compiled into the Dakota executable. The test functions
  allow for rapid testing of algorithms without process creation
  overhead or engineering simulation expense.

- The grid case is deprecated, but was an experiment in interfacing
  Dakota to distributed computing engines.

When employing algebraic mappings, the AMPL solver library \cite Gay97
is used to evaluate a directed acyclic graph (DAG) specification from
a separate stub.nl file. Separate stub.col and stub.row files are also
required to declare the string identifiers of the subset of inputs and
outputs, respectively, that will be used in the algebraic mappings.

Faq::
See_Also::	
