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// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later
// SPDX-FileCopyrightText: Bradley M. Bell <bradbell@seanet.com>
// SPDX-FileContributor: 2003-22 Bradley M. Bell
// ----------------------------------------------------------------------------
/*
{xrst_begin exp_2_rev1.cpp}
exp_2: Verify First Order Reverse Sweep
#######################################
{xrst_spell_off}
{xrst_code cpp} */
# 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;
}
/* {xrst_code}
{xrst_spell_on}
{xrst_end exp_2_rev1.cpp}
*/
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