// $Id$
# ifndef CPPAD_CSKIP_OP_INCLUDED
# define CPPAD_CSKIP_OP_INCLUDED

/* --------------------------------------------------------------------------
CppAD: C++ Algorithmic Differentiation: Copyright (C) 2003-14 Bradley M. Bell

CppAD is distributed under multiple licenses. This distribution is under
the terms of the 
                    GNU General Public License Version 3.

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.
-------------------------------------------------------------------------- */

namespace CppAD { // BEGIN_CPPAD_NAMESPACE
/*!
\file cskip_op.hpp
Zero order forward mode set which operations to skip.
*/

/*!
Zero order forward mode execution of op = CSkipOp.

\tparam Base
base type for the operator; i.e., this operation was recorded
using AD< \a Base > and computations by this routine are done using type
\a Base.

\param i_z
variable index corresponding to the result of the previous operation.
This is used for error checking. To be specific,
the left and right operands for the CExpOp operation must have indexes
less than or equal this value.

\param arg [in]
\n
\a arg[0]
is static cast to size_t from the enum type
\verbatim
	enum CompareOp {
		CompareLt, 
		CompareLe, 
		CompareEq, 
		CompareGe, 
		CompareGt, 
		CompareNe
	}
\endverbatim
for this operation.
Note that arg[0] cannot be equal to CompareNe.
\n
\n
\a arg[1] & 1
\n
If this is zero, left is a a parameter. Otherwise it is a variable.
\n
\n
\a arg[1] & 2
\n
If this is zero, right is a parameter. Otherwise it is a variable.
\n
\a arg[2] 
is the index corresponding to left in comparision.
\n
\a arg[3] 
is the index corresponding to right in comparision.
\n
\a arg[4] 
is the number of operations to skip if the comparision result is true.
\n
\a arg[5] 
is the number of operations to skip if the comparision result is false.
\n
<tt>arg[5+i]</tt>
for <tt>i = 1 , ... , arg[4]</tt> are the operations to skip if the
comparision result is true.
\n
<tt>arg[5+arg[4]+i]</tt>
for <tt>i = 1 , ... , arg[5]</tt> are the operations to skip if the
comparision result is false.

\param num_par [in]
is the total number of values in the vector \a parameter.

\param parameter [in]
If left is a parameter,
<code>parameter [ arg[2] ]</code> is its value.
If right is a parameter,
<code>parameter [ arg[3] ]</code> is its value.

\param cap_order [in]
number of columns in the matrix containing the Taylor coefficients.

\param taylor [in]
If left is a variable,
<code>taylor [ arg[2] * cap_order + 0 ]</code>
is the zeroth order Taylor coefficient corresponding to left.
If right is a variable,
<code>taylor [ arg[3] * cap_order + 0 ]</code>
is the zeroth order Taylor coefficient corresponding to right.

\param \cskip_op [in,out]
is vector specifying which operations are at this point are know to be
unecessary and can be skipped. 
This is both an input and an output.
*/
template <class Base>
inline void forward_cskip_op_0(
	size_t               i_z            ,
	const addr_t*        arg            ,
	size_t               num_par        ,
	const Base*          parameter      ,
	size_t               cap_order      ,
	Base*                taylor         ,
	bool*                cskip_op       )
{
	CPPAD_ASSERT_UNKNOWN( size_t(arg[0]) < size_t(CompareNe) );
	CPPAD_ASSERT_UNKNOWN( arg[1] != 0 );

	Base left, right;
	if( arg[1] & 1 )
	{	// If varialbe arg[2] <= i_z, it has already been computed,
		// but it will be skipped for higher orders.
		left = taylor[ arg[2] * cap_order + 0 ];
		CPPAD_ASSERT_UNKNOWN( IdenticalPar(left) );
	}
	else
	{	CPPAD_ASSERT_UNKNOWN( size_t(arg[2]) < num_par );
		left = parameter[ arg[2] ];
		CPPAD_ASSERT_UNKNOWN( IdenticalPar(left) );
	}
	if( arg[1] & 2 )
	{	// If varialbe arg[3] <= i_z, it has already been computed,
		// but it will be skipped for higher orders.
		right = taylor[ arg[3] * cap_order + 0 ];
		CPPAD_ASSERT_UNKNOWN( IdenticalPar(right) );
	}
	else
	{	CPPAD_ASSERT_UNKNOWN( size_t(arg[3]) < num_par );
		right = parameter[ arg[3] ];
		CPPAD_ASSERT_UNKNOWN( IdenticalPar(right) );
	}


	// initialize to avoid compiler warning
	bool true_case = false;
	Base diff      = left - right;
	switch( CompareOp( arg[0] ) )
	{
		case CompareLt:
		true_case = LessThanZero(diff);
		break;

		case CompareLe:
		true_case = LessThanOrZero(diff);
		break;

		case CompareEq:
		true_case = IdenticalZero(diff);
		break;

		case CompareGe:
		true_case = GreaterThanOrZero(diff);
		break;

		case CompareGt:
		true_case = GreaterThanZero(diff);
		break;

		case CompareNe:
		true_case = ! IdenticalZero(diff);
		break;

		default:
		CPPAD_ASSERT_UNKNOWN(false);
	}
	if( true_case )
	{	for(size_t i = 0; i < size_t(arg[4]); i++)
			cskip_op[ arg[6+i] ] = true; 
	}
	else
	{	for(size_t i = 0; i < size_t(arg[5]); i++)
			cskip_op[ arg[6+arg[4]+i] ] = true; 
	}
	return;
}
} // END_CPPAD_NAMESPACE
# endif