AD Binary Subtraction: Example and Test
Keywords: ad binary subtraction: example test - subtract minus

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AD Binary Subtraction: Example and Test
`

    # include <cppad/cppad.hpp>

    bool Sub(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(1);
    	x[0]      = x0;

    	// declare independent variables and start tape recording
    	CppAD::Independent(x);

    	AD<double> a = 2. * x[0] - 1.; // AD<double> - double
    	AD<double> b = a  - 2;         // AD<double> - int
    	AD<double> c = 3. - b;         // double     - AD<double>
    	AD<double> d = 4  - c;         // int        - AD<double>

    	// range space vector
    	size_t m = 1;
    	CPPAD_TESTVECTOR(AD<double>) y(m);
    	y[0] = x[0] - d;              // AD<double> - AD<double>

    	// create f: x -> y and stop tape recording
    	CppAD::ADFun<double> f(x, y);

    	// check value
    	ok &= NearEqual(y[0], x0-4.+3.+2.-2.*x0+1.,  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], -1., 1e-10, 1e-10);

    	// reverse computation of derivative of y[0]
    	CPPAD_TESTVECTOR(double)  w(m);
    	CPPAD_TESTVECTOR(double) dw(n);
    	w[0]  = 1.;
    	dw    = f.Reverse(1, w);
    	ok   &= NearEqual(dw[0], -1., 1e-10, 1e-10);

    	// use a VecAD<Base>::reference object with subtraction
    	CppAD::VecAD<double> v(1);
    	AD<double> zero(0);
    	v[zero] = b;
    	AD<double> result = 3. - v[zero];
    	ok     &= (result == c);

    	return ok;
    }

`

Input File: example/sub.cpp