Convert an AD Variable to a Parameter: Example and Test
Keywords: convert ad variable to parameter: example test Var2par Value during taping

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Convert an AD Variable to a Parameter: Example and Test
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    # include <cppad/cppad.hpp>

    bool Var2Par(void)
    {	bool ok = true;
    	using CppAD::AD;
    	using CppAD::Value;
    	using CppAD::Var2Par;

    	// domain space vector
    	size_t n = 2;
    	CPPAD_TESTVECTOR(AD<double>) x(n);
    	x[0] = 3.;
    	x[1] = 4.;

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

    	// range space vector
    	size_t m = 1;
    	CPPAD_TESTVECTOR(AD<double>) y(m);
    	y[0] = - x[1] * Var2Par(x[0]);    // same as y[0] = -x[1] * 3.;

    	// cannot call Value(x[j]) or Value(y[0]) here (currently variables)
    	ok &= ( Value( Var2Par(x[0]) ) == 3. );
    	ok &= ( Value( Var2Par(x[1]) ) == 4. );
    	ok &= ( Value( Var2Par(y[0]) ) == -12. );

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

    	// can call Value(x[j]) or Value(y[0]) here (currently parameters)
    	ok &= (Value(x[0]) ==  3.);
    	ok &= (Value(x[1]) ==  4.);
    	ok &= (Value(y[0]) == -12.);

    	// evaluate derivative of y w.r.t x
    	CPPAD_TESTVECTOR(double) w(m);
    	CPPAD_TESTVECTOR(double) dw(n);
    	w[0] = 1.;
    	dw   = f.Reverse(1, w);
    	ok  &= (dw[0] == 0.);  // derivative of y[0] w.r.t x[0] is zero
    	ok  &= (dw[1] == -3.); // derivative of y[0] w.r.t x[1] is 3

    	return ok;
    }

`

Input File: example/var2par.cpp