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lines 8-91 of file: include/cppad/core/parallel_ad.hpp
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{xrst_begin parallel_ad}
{xrst_spell
   rosen
   runge
   teardown
}

Enable AD Calculations During Parallel Mode
###########################################

Syntax
******
| ``parallel_ad`` < *Base* >()

Purpose
*******
The function
``parallel_ad`` < *Base* >()
must be called before any ``AD`` < *Base>* objects are used
in :ref:`parallel<ta_in_parallel-name>` mode.
In addition, if this routine is called after one is done using
parallel mode, it will free extra memory used to keep track of
the multiple ``AD`` < *Base* > tapes required for parallel execution.

Discussion
**********
By default, for each ``AD`` < *Base* > class there is only one
tape that records :ref:`glossary@AD of Base` operations.
This tape is a global variable and hence it cannot be used
by multiple threads at the same time.
The :ref:`parallel_setup<ta_parallel_setup-name>` function informs CppAD of the
maximum number of threads that can be active in parallel mode.
This routine does extra setup
(and teardown) for the particular *Base* type.

CheckSimpleVector
*****************
This routine has the side effect of calling ``CheckSimpleVector`` for
some of the possible
:ref:`CheckSimpleVector@Scalar` and :ref:`CheckSimpleVector@Vector` cases.
The set of these cases may increase in the future and currently includes
the following:

.. csv-table::
   :header: Scalar, Vector

   ``bool``          , ``CppAD::vectorBool``
   ``size_t``        , ``CppAD::vector<size_t>``
   *Base*            , *vector* < *Base* >
   ``AD`` < *Base* > , *vector* ``AD`` < *Base* >

Where *vector* above is
``CppAD::vector`` ,
``std::vector`` , and
the :ref:`cppad_testvector-name` .


Example
*******
The files
:ref:`openmp_get_started.cpp-name` ,
:ref:`bthread_get_started.cpp-name` , and
:ref:`pthread_get_started.cpp-name` ,
contain examples and tests that implement this function.

Restriction
***********
This routine cannot be called in parallel mode or while
there is a tape recording ``AD`` < *Base* > operations.

Other Initialization
********************
If the following routines have static memory and must be called once
before being used in parallel mode:

#. :ref:`CheckSimpleVector <CheckSimpleVector@Parallel Mode>`
#. :ref:`thread_alloc, memory_leak <ta_parallel_setup-name>`
#. :ref:`Rosen34 <Rosen34@Parallel Mode>`
#. :ref:`Runge45 <Runge45@Parallel Mode>`
#. :ref:`discrete <Discrete@Parallel Mode>`
#. :ref:`atomic_one <atomic_one@afun@Parallel Mode>`


{xrst_end parallel_ad}