Converting CppAD::AD<double> to double in cpp - c++

Question

I'm using CppAD with Ipopt. In some places I have to typecast the AD format to its base format that is double. I have used CppAD::Value(AD var) it gives me output in double format.
But considering line no.27 the code is fine during compile time. Its showing the following error in runtime. The error is :
cppad-20160000.1 error from a known source:
Value: argument is a variable (not a parameter)
Error detected by false result for
Parameter(x)
at line 89 in the file
/usr/include/cppad/local/value.hpp
I have attached the code I'm running for verification. Kindly help. please install Ipopt before running the code.
The type of value is still CppAD::AD . But the Value() is not working.
#include <cppad/ipopt/solve.hpp>
#include <iostream>
namespace {
using CppAD::AD;
class FG_eval {
public:
typedef CPPAD_TESTVECTOR( AD<double> ) ADvector;
void operator()(ADvector& fg, const ADvector& x)
{ assert( fg.size() == 3 );
assert( x.size() == 4 );
// Fortran style indexing
AD<double> x1 = x[0];
AD<double> x2 = x[1];
AD<double> x3 = x[2];
AD<double> x4 = x[3];
// f(x)
fg[0] = x1 * x4 * (x1 + x2 + x3) + x3;
// g_1 (x)
fg[1] = x1 * x2 * x3 * x4;
// g_2 (x)
fg[2] = x1 * x1 + x2 * x2 + x3 * x3 + x4 * x4;
// help on this line
std::cout << CppAD::Value(x1) << std::endl;
//
return;
}
};
}
bool get_started()
{ bool ok = true;
size_t i;
typedef CPPAD_TESTVECTOR( double ) Dvector;
// number of independent variables (domain dimension for f and g)
size_t nx = 4;
// number of constraints (range dimension for g)
size_t ng = 2;
// initial value of the independent variables
Dvector xi(nx);
xi[0] = 1.0;
xi[1] = 5.0;
xi[2] = 5.0;
xi[3] = 1.0;
// lower and upper limits for x
Dvector xl(nx), xu(nx);
for(i = 0; i < nx; i++)
{ xl[i] = 1.0;
xu[i] = 5.0;
}
// lower and upper limits for g
Dvector gl(ng), gu(ng);
gl[0] = 25.0; gu[0] = 1.0e19;
gl[1] = 40.0; gu[1] = 40.0;
// object that computes objective and constraints
FG_eval fg_eval;
// options
std::string options;
// turn off any printing
options += "Integer print_level 0\n";
options += "String sb yes\n";
// maximum number of iterations
options += "Integer max_iter 10\n";
// approximate accuracy in first order necessary conditions;
// see Mathematical Programming, Volume 106, Number 1,
// Pages 25-57, Equation (6)
options += "Numeric tol 1e-6\n";
// derivative testing
options += "String derivative_test second-order\n";
// maximum amount of random pertubation; e.g.,
// when evaluation finite diff
options += "Numeric point_perturbation_radius 0.\n";
// place to return solution
CppAD::ipopt::solve_result<Dvector> solution;
// solve the problem
CppAD::ipopt::solve<Dvector, FG_eval>(
options, xi, xl, xu, gl, gu, fg_eval, solution
);
//
// Check some of the solution values
//
ok &= solution.status == CppAD::ipopt::solve_result<Dvector>::success;
//
double check_x[] = { 1.000000, 4.743000, 3.82115, 1.379408 };
double check_zl[] = { 1.087871, 0., 0., 0. };
double check_zu[] = { 0., 0., 0., 0. };
double rel_tol = 1e-6; // relative tolerance
double abs_tol = 1e-6; // absolute tolerance
for(i = 0; i < nx; i++)
{ ok &= CppAD::NearEqual(
check_x[i], solution.x[i], rel_tol, abs_tol
);
ok &= CppAD::NearEqual(
check_zl[i], solution.zl[i], rel_tol, abs_tol
);
ok &= CppAD::NearEqual(
check_zu[i], solution.zu[i], rel_tol, abs_tol
);
}
return ok;
}
int main()
{
get_started();
return 0;
}
cmakelists.txt
cmake_minimum_required(VERSION 3.5)
project(jnk)
add_compile_options(-std=c++11)
add_executable(${PROJECT_NAME} testCppAD.cpp)
target_link_libraries(${PROJECT_NAME}
ipopt z uv
)

Answer 1

I found out the answer. We have to use an inbuilt function CppAD::Var2Par() before using CppAD::Value(). Will work.