AD Computed Assignment Multiplication: Example and Test
Keywords: ad computed assignment multiplication: example test *= multiply assign plus add

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AD Computed Assignment Multiplication: Example and Test
`

    # 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_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 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_TESTVECTOR(double) dx(n);
    	CPPAD_TESTVECTOR(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_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, 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;
    }

`

Input File: example/mul_eq.cpp