\(\newcommand{\W}[1]{ \; #1 \; }\) \(\newcommand{\R}[1]{ {\rm #1} }\) \(\newcommand{\B}[1]{ {\bf #1} }\) \(\newcommand{\D}[2]{ \frac{\partial #1}{\partial #2} }\) \(\newcommand{\DD}[3]{ \frac{\partial^2 #1}{\partial #2 \partial #3} }\) \(\newcommand{\Dpow}[2]{ \frac{\partial^{#1}}{\partial {#2}^{#1}} }\) \(\newcommand{\dpow}[2]{ \frac{ {\rm d}^{#1}}{{\rm d}\, {#2}^{#1}} }\)

json_comp_op.cpp

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Json Comparison Operators: Example and Test

Source Code

# include <cppad/cppad.hpp>

bool comp_op(void)
{  bool ok = true;
   using CppAD::vector;
   using CppAD::AD;
   double eps99 = 99.0 * std::numeric_limits<double>::epsilon();
   //
   // AD graph example
   // node_1 : p[0]
   // node_2 : x[0]
   //        : x[0] < p[0]
   // node_3 : p[0] - x[0]
   // node_4 : log( p[0] - x[0] )
   // y[0]   = log( p[0] - x[0] )
   // use single quote to avoid having to escape double quote
   std::string json =
      "{\n"
      "   'function_name'  : 'comp_op example',\n"
      "   'op_define_vec'  : [ 3, [\n"
      "       { 'op_code':1, 'name':'comp_lt'            } ,\n"
      "       { 'op_code':2, 'name':'sub',     'n_arg':2 } ,\n"
      "       { 'op_code':3, 'name':'log',     'n_arg':1 } ]\n"
      "   ],\n"
      "   'n_dynamic_ind'  : 1,\n"
      "   'n_variable_ind' : 1,\n"
      "   'constant_vec'   : [ 0, [ ] ],\n"
      "   'op_usage_vec'   : [ 3, [\n"
      "       [ 1, 0, 2, [2, 1 ] ] ,\n" // x[0] < p[0]
      "       [ 2, 1, 2          ] ,\n" // p[0] - x[0]
      "       [ 3, 3             ] ]\n" // log( p[0] - x[0] )
      "   ],\n"
      "   'dependent_vec' : [ 1, [4] ] \n"
      "}\n";
   // Convert the single quote to double quote
   for(size_t i = 0; i < json.size(); ++i)
      if( json[i] == '\'' ) json[i] = '"';
   //
   // f(x, p) = log( p[0] - x[0] )
   CppAD::ADFun<double> f;
   f.from_json(json);
   ok &= f.Domain() == 1;
   ok &= f.Range() == 1;
   ok &= f.size_dyn_ind() == 1;
   //
   // set independent variables and parameters
   vector<double> p(1), x(1);
   p[0] = 0.3;
   x[0] = 0.2;
   //
   // compute y = f(x, p)
   f.new_dynamic(p);
   vector<double> y = f.Forward(0, x);
   //
   //  x[0] < p[0] so comparison should not have changed
   ok &= f.compare_change_number() == 0;
   //
   // check result
   double check = std::log( p[0] - x[0] );
   ok &= CppAD::NearEqual(y[0], check, eps99, eps99);
   //
   // case where comparison is false
   f.check_for_nan(false); // suppress checking for nan for this test
   x[0] = 0.4;
   y = f.Forward(0, x);
   ok &= f.compare_change_number() == 1;
   //
   // -----------------------------------------------------------------------
   // Convert to Json graph and back again
   json = f.to_json();
   // std::cout << json;
   f.from_json(json);
   // -----------------------------------------------------------------------
   //
   // compute y = f(x, p)
   f.new_dynamic(p);
   x[0] = 0.2;
   y = f.Forward(0, x);
   //
   // check result
   ok &= CppAD::NearEqual(y[0], check, eps99, eps99);
   //
   // case where comparison is false
   x[0] = 0.4;
   y = f.Forward(0, x);
   ok &= f.compare_change_number() == 1;
   //
   return ok;
}