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

json_div_op.cpp

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Json div Operator: Example and Test

Source Code

# include <cppad/cppad.hpp>

bool div_op(void)
{  bool ok = true;
   using CppAD::vector;
   using CppAD::AD;
   using CppAD::NearEqual;
   double eps99 = 99.0 * std::numeric_limits<double>::epsilon();
   //
   // AD graph example
   // node_1 : p[0]
   // node_2 : p[1]
   // node_3 : x[0]
   // node_4 : p[0] / p[1]
   // node_5 : x[0] / ( p[1] / p[0] )
   // y[0]   = p[0] / p[1]
   // y[1]   = x[0] / ( p[0] / p[1] )
   // use single quote to avoid having to escape double quote
   std::string json =
      "{\n"
      "   'function_name'  : 'div example',\n"
      "   'op_define_vec'  : [ 1, [\n"
      "       { 'op_code':1, 'name':'div', 'n_arg':2 } ]\n"
      "   ],\n"
      "   'n_dynamic_ind'  : 2,\n"
      "   'n_variable_ind' : 1,\n"
      "   'constant_vec'   : [ 0, [ ] ],\n"
      "   'op_usage_vec'   : [ 2, [\n"
      "       [ 1, 1, 2 ] ,\n" // p[0] / p[1]
      "       [ 1, 3, 4 ] ]\n" // x[0] / ( p[0] / p[1] )
      "   ],\n"
      "   'dependent_vec' : [ 2, [4, 5] ] \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) = [ p_0 / p_1 , x_0 * p_1 / p_0 ]
   CppAD::ADFun<double> f;
   f.from_json(json);
   //
   ok &= f.Domain() == 1;
   ok &= f.Range() == 2;
   ok &= f.size_dyn_ind() == 2;
   //
   // set independent variables and parameters
   vector<double> p(2), x(1);
   p[0] = 2.0;
   p[1] = 3.0;
   x[0] = 4.0;
   //
   // compute y = f(x, p)
   f.new_dynamic(p);
   vector<double> y = f.Forward(0, x);
   //
   // check result
   ok &= NearEqual(y[0] , p[0] / p[1] , eps99, eps99 );
   ok &= NearEqual(y[1] , x[0] / ( p[0] / p[1] ), eps99, eps99 );
   // -----------------------------------------------------------------------
   // Convert to Json graph and back again
   json = f.to_json();
   // std::cout << "json = " << json;
   f.from_json(json);
   // -----------------------------------------------------------------------
   ok &= f.Domain() == 1;
   ok &= f.Range() == 2;
   ok &= f.size_dyn_ind() == 2;
   //
   // set independent variables and parameters
   p[0] = 2.0;
   p[1] = 3.0;
   x[0] = 4.0;
   //
   // compute y = f(x, p)
   f.new_dynamic(p);
   y = f.Forward(0, x);
   //
   // check result
   ok &= NearEqual(y[0] , p[0] / p[1] , eps99, eps99 );
   ok &= NearEqual(y[1] , x[0] / ( p[0] / p[1] ), eps99, eps99 );
   //
   return ok;
}