/* $Id$ */
/* --------------------------------------------------------------------------
CppAD: C++ Algorithmic Differentiation: Copyright (C) 2003-15 Bradley M. Bell

CppAD is distributed under multiple licenses. This distribution is under
the terms of the 
                    Eclipse Public License Version 1.0.

A copy of this license is included in the COPYING file of this distribution.
Please visit http://www.coin-or.org/CppAD/ for information on other licenses.
-------------------------------------------------------------------------- */
$begin CompareChange$$
$spell 
	const
$$

$section Comparison Changes During Zero Order Forward Mode$$

$index ADFun, CompareChange$$
$index CompareChange, ADFun$$
$index zero, order forward$$
$index forward, zero order$$

$head Syntax$$
$icode%c% = %f%.CompareChange()%$$
$pre
$$
$bold See Also$$
$cref FunCheck$$

$head Deprecated 20150120$$
This routine has been deprecated, use $cref compare_change$$
instead.

$head Purpose$$
We use $latex F : B^n \rightarrow B^m$$ to denote the
$cref/AD function/glossary/AD Function/$$ corresponding to $icode f$$.
This function may be not agree with the algorithm that was used
to create the corresponding
AD of $icode Base$$
$cref/operation sequence/glossary/Operation/Sequence/$$
because of changes in AD
$cref/comparison/Compare/$$ results.
The $code CompareChange$$ function can be used to detect these changes.

$head f$$
The object $icode f$$ has prototype
$codei%
	const ADFun<%Base%> %f%
%$$

$head c$$
The result $icode c$$ has prototype
$codei%
	size_t %c%
%$$
It is the number of 
$codei%AD<%Base%>%$$ $cref/comparison/Compare/$$ 
operations,
corresponding to the previous call to $cref Forward$$ 
$codei%
	%f%.Forward(0, %x%)
%$$
that have a different result from
when $icode F$$ was created by taping an algorithm.

$head Discussion$$
If $icode c$$ is not zero, 
the boolean values resulting from some of the 
$cref/comparison operations/Compare/$$ corresponding to $icode x$$
are different from when the 
AD of $icode Base$$
$cref/operation sequence/glossary/Operation/Sequence/$$ was created.
In this case, you may want to re-tape the algorithm with the
$cref/independent variables/glossary/Tape/Independent Variable/$$ 
equal to the values in $icode x$$ 
(so AD operation sequence properly represents the algorithm
for this value of independent variables).
On the other hand, re-taping the AD operation sequence usually takes 
significantly more time than evaluation using $cref forward_zero$$.
If the functions values have not changed (see $cref FunCheck$$)
it may not be worth re-taping a new AD operation sequence. 


$end