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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
// ----------------------------------------------------------------------------
# include <cppad/cppad.hpp>
bool log1p(void)
{ bool ok = true;
using CppAD::AD;
using CppAD::NearEqual;
// 10 times machine epsilon
double eps = 10. * std::numeric_limits<double>::epsilon();
// domain space vector
size_t n = 1;
double x0 = 0.5;
CPPAD_TESTVECTOR(AD<double>) ax(n);
ax[0] = x0;
// declare independent variables and start tape recording
CppAD::Independent(ax);
// a temporary value
AD<double> expm1_of_x0 = CppAD::expm1(ax[0]);
// range space vector
size_t m = 1;
CPPAD_TESTVECTOR(AD<double>) ay(m);
ay[0] = CppAD::log1p(expm1_of_x0);
// create f: x -> y and stop tape recording
CppAD::ADFun<double> f(ax, ay);
// check value
ok &= NearEqual(ay[0] , x0, eps, eps);
// forward computation of first partial w.r.t. x[0]
CPPAD_TESTVECTOR(double) dx(n);
CPPAD_TESTVECTOR(double) dy(m);
dx[0] = 1.;
dy = f.Forward(1, dx);
ok &= NearEqual(dy[0], 1., eps, eps);
// forward computation of higher order partials w.r.t. x[0]
size_t n_order = 5;
for(size_t order = 2; order < n_order; order++)
{ dx[0] = 0.;
dy = f.Forward(order, dx);
ok &= NearEqual(dy[0], 0., eps, eps);
}
// reverse computation of derivatives
CPPAD_TESTVECTOR(double) w(m);
CPPAD_TESTVECTOR(double) dw(n_order * n);
w[0] = 1.;
dw = f.Reverse(n_order, w);
ok &= NearEqual(dw[0], 1., eps, eps);
for(size_t order = 1; order < n_order; order++)
ok &= NearEqual(dw[order * n + 0], 0., eps, eps);
return ok;
}
// END C++
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