Blurb::
Perform evaluations in batches

Description::
When the optional \c batch keyword is used, %Dakota performs
evaluations in batches. In batch mode, %Dakota writes the parameters
for multiple (a batch of) evaluations to a single file, invokes 
the analysis driver once for the whole batch, and expects 
to find results for the entire batch in a single file after
the analysis driver has exited. Batch mode may be useful 
when a user desires to take greater control over job management.
For example, the analysis driver can perform the evaluations in 
the batch in any sequence or in concurrent sub-batches.

The names of the parameters file and results file are provided
as command line arguments to the analysis driver, just as in
a conventional, non-batch evaluation. By default, all currently
available evaluations will be performed in a single batch, but
the batch size can be limited using the \ref interface-batch-size
keyword.

Batch mode has a few important limitations.

\li Only one batch at a time may be executed. Asynchronous
    execution of multiple concurrent batches is not supported.
\li No \ref interface-analysis_drivers-input_filter or 
    \ref interface-analysis_drivers-output_filter is permitted.
\li Only one \c analysis_driver is allowed.
\li \c failure_capture modes are restricted to 
    \ref interface-failure_capture-abort and 
    \ref interface-failure_capture-recover.

Some of these restrictions may be lifted in future %Dakota releases.

<b>File Formats</b>

A batch parameters file written by %Dakota is simply a
concatenated set of parameters files for the set of evaluations, either
in \ref interface-analysis_drivers-fork-aprepro or default Dakota
format.

The batch results file is also a concatenated set of results files
for the individual evaluations. However, because %Dakota's results 
file format is not as rich as its parameters file format, 
evaluations in the batch results file must be separated by a line 
that begins with the '#' character.

The order of evaluations in the batch results file must match the order
in the batch parameters file.

<b>Tagging and Work Directories</b>

When %Dakota's \ref interface-analysis_drivers-fork-work_directory
feature is enabled, one directory is created per batch. If 
\ref interface-analysis_drivers-fork-file_tag or 
\ref interface-analysis_drivers-fork-work_directory-directory_tag
is used, parameters/results files and work directories are tagged
with a batch Id, which is an integer that begins with 1 and increments
for each new batch.

Topics::	concurrency_and_parallelism
Examples::
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