![]() |
Prev | Next | MulEq.cpp | Headings |
# include <cppad/cppad.hpp>
bool MulEq(void)
{ bool ok = true;
using CppAD::AD;
using CppAD::NearEqual;
// domain space vector
size_t n = 1;
double x0 = .5;
CPPAD_TEST_VECTOR< AD<double> > x(n);
x[0] = x0;
// declare independent variables and start tape recording
CppAD::Independent(x);
// range space vector
size_t m = 2;
CPPAD_TEST_VECTOR< AD<double> > y(m);
y[0] = x[0]; // initial value
y[0] *= 2; // AD<double> *= int
y[0] *= 4.; // AD<double> *= double
y[1] = y[0] *= x[0]; // use the result of a computed assignment
// create f: x -> y and stop tape recording
CppAD::ADFun<double> f(x, y);
// check value
ok &= NearEqual(y[0] , x0*2.*4.*x0, 1e-10 , 1e-10);
ok &= NearEqual(y[1] , y[0], 1e-10 , 1e-10);
// forward computation of partials w.r.t. x[0]
CPPAD_TEST_VECTOR<double> dx(n);
CPPAD_TEST_VECTOR<double> dy(m);
dx[0] = 1.;
dy = f.Forward(1, dx);
ok &= NearEqual(dy[0], 8.*2.*x0, 1e-10, 1e-10);
ok &= NearEqual(dy[1], 8.*2.*x0, 1e-10, 1e-10);
// reverse computation of derivative of y[0]
CPPAD_TEST_VECTOR<double> w(m);
CPPAD_TEST_VECTOR<double> dw(n);
w[0] = 1.;
w[1] = 0.;
dw = f.Reverse(1, w);
ok &= NearEqual(dw[0], 8.*2.*x0, 1e-10, 1e-10);
// use a VecAD<Base>::reference object with computed multiplication
CppAD::VecAD<double> v(1);
AD<double> zero(0);
AD<double> result = 1;
v[zero] = 2;
result *= v[zero];
ok &= (result == 2);
return ok;
}