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@(@\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}} }@)@
Printing During Forward Mode: Example and Test

Running
To build this program and run its correctness test see cmake_check .

Source Code
# include <cppad/cppad.hpp>

namespace {
     using std::cout;
     using std::endl;
     using CppAD::AD;

     // use of PrintFor to check for invalid function arguments
     AD<double> check_log(const AD<double>& y)
     {     // check during recording
          if( y <= 0. )
               cout << "check_log: y = " << y << " is <= 0" << endl;

          // check during zero order forward calculation
          PrintFor(y, "check_log: y == ", y , " which is <= 0\n");

          return log(y);
     }
}

void print_for(void)
{     using CppAD::PrintFor;

     // independent variable vector
     size_t n = 1;
     CPPAD_TESTVECTOR(AD<double>) ax(n);
     ax[0] = 1.;
     Independent(ax);

     // print a VecAD<double>::reference object that is a parameter
     CppAD::VecAD<double> av(1);
     AD<double> Zero(0);
     av[Zero] = 0.;
     PrintFor("v[0] = ", av[Zero]);

     // Print a newline to separate this from previous output,
     // then print an AD<double> object that is a variable.
     PrintFor("\nv[0] + x[0] = ", av[0] + ax[0]);

     // A conditional print that will not generate output when x[0] = 2.
     PrintFor(ax[0], "\n  2. + x[0] = ",   2. + ax[0], "\n");

     // A conditional print that will generate output when x[0] = 2.
     PrintFor(ax[0] - 2., "\n  3. + x[0] = ",   3. + ax[0], "\n");

     // A log evaluations that will result in an error message when x[0] = 2.
     AD<double> var     = 2. - ax[0];
     AD<double> log_var = check_log(var);

     // dependent variable vector
     size_t m = 2;
     CPPAD_TESTVECTOR(AD<double>) ay(m);
     ay[0] = av[Zero] + ax[0];

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

     // zero order forward with x[0] = 2
     CPPAD_TESTVECTOR(double) x(n);
     x[0] = 2.;

     cout << "v[0] = 0" << endl;
     cout << "v[0] + x[0] = 2" << endl;
     cout << "  3. + x[0] = 5" << endl;
     cout << "check_log: y == 0 which is <= 0" << endl;
     // ./makefile.am expects "Test passes" at beginning of next output line
     cout << "Test passes if four lines above repeat below:" << endl;
     f.Forward(0, x);

     return;
}
int main(void)
{     print_for();

     return 0;
}

Output
Executing the program above generates the following output:
 
     v[0] = 0
     v[0] + x[0] = 2
     Test passes if two lines above repeat below:
     v[0] = 0
     v[0] + x[0] = 2

Input File: example/print_for/print_for.cpp