# 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);
int i;
for(i = 0; i < int(m); i++)
y[i] = CppAD::pow(x[0], i - 3);
// create f: x -> y and stop tape recording
CppAD::ADFun<double> f(x, y);
// check value
double check;
for(i = 0; i < int(m); i++)
{ check = std::pow(x0, double(i - 3));
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(i = 0; i < int(m); i++)
{ check = double(i-3) * std::pow(x0, double(i - 4));
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(i = 0; i < int(m); i++)
w[i] = 0.;
for(i = 0; i < int(m); i++)
{ w[i] = 1.;
dw = f.Reverse(1, w);
check = double(i-3) * std::pow(x0, double(i - 4));
ok &= NearEqual(dw[0] , check, eps99 , eps99);
w[i] = 0.;
}
return ok;
}