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$\newcommand{\W}[1]{ \; #1 \; } \newcommand{\R}[1]{ {\rm #1} } \newcommand{\B}[1]{ {\bf #1} } \newcommand{\D}[2]{ \frac{\partial #1}{\partial #2} } \newcommand{\DD}[3]{ \frac{\partial^2 #1}{\partial #2 \partial #3} } \newcommand{\Dpow}[2]{ \frac{\partial^{#1}}{\partial {#2}^{#1}} } \newcommand{\dpow}[2]{ \frac{ {\rm d}^{#1}}{{\rm d}\, {#2}^{#1}} }$
AD Compound Assignment Multiplication: Example and Test
# include <cppad/cppad.hpp> bool MulEq(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(n); x[0] = x0; // declare independent variables and start tape recording CppAD::Independent(x); // range space vector size_t m = 2; CPPAD_TESTVECTOR(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 compound 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, eps99, eps99); ok &= NearEqual(y[1] , y[0], 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], 8.*2.*x0, eps99, eps99); ok &= NearEqual(dy[1], 8.*2.*x0, eps99, eps99); // reverse computation of derivative of y[0] CPPAD_TESTVECTOR(double) w(m); CPPAD_TESTVECTOR(double) dw(n); w[0] = 1.; w[1] = 0.; dw = f.Reverse(1, w); ok &= NearEqual(dw[0], 8.*2.*x0, eps99, eps99); // 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; } 
Input File: example/general/mul_eq.cpp