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

from_json.cpp

View page source

Convert Jason Graph to an ADFun Object: Example and Test

Source Code

# include <cppad/cppad.hpp>

bool from_json(void)
{  bool ok = true;
   using CppAD::vector;
   //
   // An AD graph example
   // node_1 : p[0]
   // node_2 : x[0]
   // node_3 : x[1]
   // node_4 : -2.0
   // node_5 : p[0] + x[0] + x[1]
   // node_6 : (p[0] + x[0] + x[1]) * (p[0] + x[0] + x[1])
   // y[0]   = (p[0] + x[0] + x[1]) * (p[0] + x[0] + x[1])
   // use single quote to avoid having to escape double quote
   std::string json =
      "{\n"
      "   'function_name'  : 'from_json example',\n"
      "   'op_define_vec'  : [ 3, [\n"
      "       { 'op_code':1, 'name':'add', 'n_arg':2 } ,\n"
      "       { 'op_code':2, 'name':'mul', 'n_arg':2 } ,\n"
      "       { 'op_code':3, 'name':'sum'            } ]\n"
      "   ],\n"
      "   'n_dynamic_ind'  : 1,\n"
      "   'n_variable_ind' : 2,\n"
      "   'constant_vec'   : [ 1, [ -2.0 ] ],\n"
      "   'op_usage_vec'   : [ 2, [\n"
      "       [ 3, 1, 3, [1, 2, 3 ] ] ,\n"
      "       [ 2, 5, 5             ] ] \n"
      "   ],\n"
      "   'dependent_vec'   : [ 1, [6] ] \n"
      "}\n";
   // Convert the single quote to double quote
   for(size_t i = 0; i < json.size(); ++i)
      if( json[i] == '\'' ) json[i] = '"';
   //
   CppAD::ADFun<double> fun;
   fun.from_json(json);
   //
   // Compute function value
   vector<double> p(1), x(2);
   p[0] = 1.0;
   x[0] = 2.0;
   x[1] = 3.0;
   fun.new_dynamic(p);
   vector<double> y = fun.Forward(0, x);
   ok  &= y[0] ==  (p[0] + x[0] + x[1]) * (p[0] + x[0] + x[1]);
   //
   // Conpute derivative value
   vector<double> jac = fun.Jacobian(x);
   ok &= jac[0] == 2.0 * (p[0] + x[0] + x[1]);
   ok &= jac[1] == 2.0 * (p[0] + x[0] + x[1]);
   //
   return ok;
}