lines 15-103 of file: include/cppad/core/chkpoint_two/chkpoint_two.hpp

{xrst_begin chkpoint_two}
{xrst_spell
   chk
}

Checkpoint Functions: Second Generation
#######################################

Syntax
******

Constructor
===========

| ``chkpoint_two`` < *Base* > *chk_fun* ( *fun* , *name* ,
| |tab| *internal_bool* , *use_hes_sparsity* , *use_base2ad* , *use_in_parallel*
| )

Use Checkpoint Function
=======================
*chk_fun* ( *ax* , *ay* )

new_dynamic
===========
*chk_fun* . ``new_dynamic`` ( *dynamic* )

Reduce Memory
*************
You can reduce the size of the tape and memory required for AD
using a checkpoint representation of a function
:math:`g : \B{R}^n \rightarrow \B{R}^m`.

Faster Recording
****************
It may also reduce the time to make a recording if the same :math:`g(x)`
is used many times (with different values) during the
recording of an ``ADFun`` < *Base* > object.

Repeating Forward
*****************
Normally, CppAD stores :ref:`forward-name` mode results,
until they freed using :ref:`capacity_order-name` ,
or the corresponding :ref:`ADFun-name` object is deleted.
This is not true for ``chkpoint_two`` functions
because the same checkpoint function may be used repeatedly
with different arguments during a single forward mode operation.
Thus, forward mode results are computed for each use of *chk_fun*
in a forward mode sweep.

Operation Sequence
******************
The :ref:`operation sequence<glossary@Operation@Sequence>`
representing :math:`g(x)` is fixed; i.e.,
it cannot depend on the value of :math:`x`.

atomic_three
************
The ``chkpoint_two`` class is derived from ``atomic_three`` ,
hence some of its error message will refer to atomic operations.
The ``chkpoint_two`` class implements all the
:ref:`atomic_three_define@Virtual Functions`
and hence its source code,

   ``include/cppad/core/chkpoint_two/chkpoint_two.hpp``

provides an example for :ref:`atomic_three-name` operations.
The difference is that ``chkpoint_two.hpp`` uses AD
instead of user provided derivatives.

Base
****
The type *Base* specifies the base type for AD operations;
i.e., *chk_fun* can be used during the recording of
``AD`` < *Base* > operations.

Contents
********
{xrst_toc_table
   include/cppad/core/chkpoint_two/ctor.hpp
   include/cppad/core/chkpoint_two/chk_fun.xrst
   include/cppad/core/chkpoint_two/dynamic.hpp
   example/chkpoint_two/get_started.cpp
   example/chkpoint_two/compare.cpp
   example/chkpoint_two/base2ad.cpp
   example/chkpoint_two/dynamic.cpp
   example/chkpoint_two/ode.cpp
}

{xrst_end chkpoint_two}