/* $Id: exp_2_rev1.cpp 2506 2012-10-24 19:36:49Z bradbell $ */
/* --------------------------------------------------------------------------
CppAD: C++ Algorithmic Differentiation: Copyright (C) 2003-07 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 exp_2_rev1.cpp$$
$spell
	cstddef
	cmath
	exp_2_rev
	bool
	std
	fabs
$$

$section exp_2: Verify First Order Reverse Sweep$$

$index reverse, exp_2$$
$index exp_2, reverse mode$$


$codep */
# include <cstddef>                 // define size_t
# include <cmath>                   // prototype for fabs
extern bool exp_2_for0(double *v0); // computes zero order forward sweep
bool exp_2_rev1(void)
{	bool ok = true;

	// set the value of v0[j] for j = 1 , ... , 5
	double v0[6];
	ok &= exp_2_for0(v0);

	// initial all partial derivatives as zero
	double f_v[6];
	size_t j;
	for(j = 0; j < 6; j++)
		f_v[j] = 0.;

	// set partial derivative for f5
	f_v[5] = 1.;
	ok &= std::fabs( f_v[5] - 1. ) <= 1e-10; // f5_v5

	// f4 = f5( v1 , v2 , v3 , v4 , v2 + v4 )
	f_v[2] += f_v[5] * 1.;
	f_v[4] += f_v[5] * 1.;
	ok &= std::fabs( f_v[2] - 1. ) <= 1e-10; // f4_v2
	ok &= std::fabs( f_v[4] - 1. ) <= 1e-10; // f4_v4

	// f3 = f4( v1 , v2 , v3 , v3 / 2 )
	f_v[3] += f_v[4] / 2.;
	ok &= std::fabs( f_v[3] - 0.5) <= 1e-10; // f3_v3

	// f2 = f3( v1 , v2 , v1 * v1 )
	f_v[1] += f_v[3] * 2. * v0[1];
	ok &= std::fabs( f_v[1] - 0.5) <= 1e-10; // f2_v1

	// f1 = f2( v1 , 1 + v1 )
	f_v[1] += f_v[2] * 1.;
	ok &= std::fabs( f_v[1] - 1.5) <= 1e-10; // f1_v1

	return ok;
}
/* $$
$end
*/
