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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 pow_int.cpp}
The Pow Integer Exponent: Example and Test
##########################################
{xrst_literal
// BEGIN C++
// END C++
}
{xrst_end pow_int.cpp}
*/
// BEGIN C++
# include <cppad/cppad.hpp>
# include <cmath>
bool pow_int(void)
{ bool ok = true;
using CppAD::AD;
using CppAD::NearEqual;
double eps99 = 99.0 * std::numeric_limits<double>::epsilon();
// declare independent variables and start tape recording
size_t n = 1;
double x0 = -0.5;
CPPAD_TESTVECTOR(AD<double>) x(n);
x[0] = x0;
CppAD::Independent(x);
// dependent variable vector
size_t m = 7;
CPPAD_TESTVECTOR(AD<double>) y(m);
for(size_t i = 0; i < m; i++)
y[i] = CppAD::pow(x[0], int(i) - 3);
// create f: x -> y and stop tape recording
CppAD::ADFun<double> f(x, y);
// check value
double check;
for(size_t i = 0; i < m; i++)
{ check = std::pow(x0, double(i) - 3.0);
ok &= NearEqual(y[i] , check, eps99 , eps99);
}
// 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);
for(size_t i = 0; i < m; i++)
{ check = (double(i) - 3.0) * std::pow(x0, double(i) - 4.0);
ok &= NearEqual(dy[i] , check, eps99 , eps99);
}
// reverse computation of derivative of y[i]
CPPAD_TESTVECTOR(double) w(m);
CPPAD_TESTVECTOR(double) dw(n);
for(size_t i = 0; i < m; i++)
w[i] = 0.;
for(size_t i = 0; i < m; i++)
{ w[i] = 1.;
dw = f.Reverse(1, w);
check = (double(i) - 3.0) * std::pow(x0, double(i) - 4.0);
ok &= NearEqual(dw[0] , check, eps99 , eps99);
w[i] = 0.;
}
return ok;
}
// END C++
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