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var2par.cpp |
Headings |
@(@\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}} }@)@
Convert an AD Variable to a Parameter: Example and Test
# 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/general/var2par.cpp