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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 sub.cpp}
AD Binary Subtraction: Example and Test
#######################################
{xrst_literal
// BEGIN C++
// END C++
}
{xrst_end sub.cpp}
*/
// BEGIN C++
# include <cppad/cppad.hpp>
bool Sub(void)
{ bool ok = true;
using CppAD::AD;
using CppAD::NearEqual;
double eps99 = 99.0 * std::numeric_limits<double>::epsilon();
// domain space vector
size_t n = 1;
double x0 = .5;
CPPAD_TESTVECTOR(AD<double>) x(1);
x[0] = x0;
// declare independent variables and start tape recording
CppAD::Independent(x);
AD<double> a = 2. * x[0] - 1.; // AD<double> - double
AD<double> b = a - 2; // AD<double> - int
AD<double> c = 3. - b; // double - AD<double>
AD<double> d = 4 - c; // int - AD<double>
// range space vector
size_t m = 1;
CPPAD_TESTVECTOR(AD<double>) y(m);
y[0] = x[0] - d; // AD<double> - AD<double>
// create f: x -> y and stop tape recording
CppAD::ADFun<double> f(x, y);
// check value
ok &= NearEqual(y[0], x0-4.+3.+2.-2.*x0+1., eps99, eps99);
// forward computation of partials 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., eps99, eps99);
// reverse computation of derivative of y[0]
CPPAD_TESTVECTOR(double) w(m);
CPPAD_TESTVECTOR(double) dw(n);
w[0] = 1.;
dw = f.Reverse(1, w);
ok &= NearEqual(dw[0], -1., eps99, eps99);
// use a VecAD<Base>::reference object with subtraction
CppAD::VecAD<double> v(1);
AD<double> zero(0);
v[zero] = b;
AD<double> result = 3. - v[zero];
ok &= (result == c);
return ok;
}
// END C++
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