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int f2cad::dscal_(integer *n, doublereal *da, doublereal *dx, integer *incx);
libf2cadCppAD.a
library routine dscal
to
compute the function
\[
f(a) =
a
\left( \begin{array}{c}
1 \\
2
\end{array} \right)
\]
We check that the derivative of this function,
calculated using the CppAD, satisfies
\[
f^{(1)} (a)
=
\left( \begin{array}{c}
1 \\
2
\end{array} \right)
\]
// standard input output library
# include <iostream>
// f2cad set up for CppAD::AD<double>
# define F2CAD_USE_CPPAD
// prototype for dscal
# include <f2cad/dscal.hpp>
int main(void)
{ using namespace CppAD;
// independent variables
size_t n = 1; // number of independent variables
CppADvector< AD<double> > a(n); // vector of independent variables
a[0] = 5.; // value of independent variables
Independent(a); // declare independent variables
// create data structure expected by dscal
AD<double> A[1];
A[0] = a[0];
integer M = 2;
AD<double> F[2];
F[0] = 1.;
F[1] = 2.;
integer Incf = 1;
// set f = a * f
f2cad::dscal_(&M, A, F, &Incf );
// dependent variables
size_t m = 2; // number of dependent variables
CppADvector< AD<double> > f(2); // vector of dependent variables
f[0] = F[0]; // value of dependent variables
f[1] = F[1];
ADFun<double> Fun(a, f); // declare dependent variables
// set differential for a
CppADvector<double> da(n);
CppADvector<double> df(m);
da[0] = 1.;
// compute differential for f
df = Fun.Forward(1, da);
// print results
std::cout << "f(a) = a * (1, 2)^T" << std::endl;
std::cout << "f'(a) = ("
<< df[0]
<< ", "
<< df[1]
<< ")^T"
<< std::endl;
if( df[0] != 1. || df[1] != 2. )
return 1; // error
return 0; // no error
}