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

graph_discrete_op.cpp

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C++ AD Graph add Operator: Example and Test

Source Code

# include <cppad/cppad.hpp>

namespace {
   double heaviside(const double &x)
   {  if( x < 0.0 )
         return 0.0;
      if( x == 0.0 )
         return 0.5;
      return 1.0;
   }
   CPPAD_DISCRETE_FUNCTION(double, heaviside)
}

bool discrete_op(void)
{  bool ok = true;
   using std::string;
   //
   // The discrete function does not exist until its AD version is called
   heaviside( CppAD::AD<double>( 0.0 ) );
   //
   // AD graph example
   // node_1 : p[0]
   // node_2 : x[0]
   // node_3 : heaviside(p[0])
   // node_4 : heaviside(p[1])
   // node_5 = heaviside(p[0]) + heaviside(p[1])
   // y[0]   = heaviside(p[0]) + heaviside(p[1])
   //
   // C++ graph object
   CppAD::cpp_graph graph_obj;
   //
   // operator being used
   CppAD::graph::graph_op_enum op_enum;
   //
   // set scalars
   graph_obj.function_name_set("discrete_op example");
   size_t n_dynamic_ind = 1;
   graph_obj.n_dynamic_ind_set(n_dynamic_ind);
   size_t n_variable_ind = 1;
   graph_obj.n_variable_ind_set(n_variable_ind);
   //
   // name_index corresponding to heaviside function
   size_t name_index = graph_obj.discrete_name_vec_size();
   graph_obj.discrete_name_vec_push_back("heaviside");
   //
   // heaviside(p[0])
   op_enum = CppAD::graph::discrete_graph_op;
   graph_obj.operator_vec_push_back(op_enum);
   graph_obj.operator_arg_push_back(name_index);  // name_index
   graph_obj.operator_arg_push_back(1);           // node arg
   //
   // heaviside(x[0])
   graph_obj.operator_vec_push_back(op_enum);
   graph_obj.operator_arg_push_back(name_index);  // name_index
   graph_obj.operator_arg_push_back(2);           // node arg
   //
   // heaviside(p[0]) + heaviside(x[0])
   op_enum = CppAD::graph::add_graph_op;
   graph_obj.operator_vec_push_back(op_enum);
   graph_obj.operator_arg_push_back(3);           // first node arg
   graph_obj.operator_arg_push_back(4);           // second node arg
   //
   // y[0] = heaviside(p[0]) + heaviside(x[0])
   graph_obj.dependent_vec_push_back(5);
   //
   // f(x, p) = heaviside(p[0]) + heaviside(x[0])
   CppAD::ADFun<double> f;
   f.from_graph(graph_obj);
   ok &= f.Domain() == 1;
   ok &= f.Range() == 1;
   ok &= f.size_dyn_ind() == 1;
   //
   // set independent variables and parameters
   CPPAD_TESTVECTOR(double) p(1), x(1);
   p[0] = 0.0;
   x[0] = 2.0;
   //
   // compute y = f(x, p)
   f.new_dynamic(p);
   CPPAD_TESTVECTOR(double) y = f.Forward(0, x);
   //
   // check result
   ok &= y[0] == heaviside(p[0]) + heaviside(x[0]);
   // -----------------------------------------------------------------------
   // Convert function to graph and back again
   f.to_graph(graph_obj);
   f.from_graph(graph_obj);
   // -----------------------------------------------------------------------
   ok &= f.Domain() == 1;
   ok &= f.Range() == 1;
   ok &= f.size_dyn_ind() == 1;
   //
   // set independent variables and parameters
   p[0] = -2.0;
   x[0] = 2.0;
   //
   // compute y = f(x, p)
   f.new_dynamic(p);
   y = f.Forward(0, x);
   //
   // check result
   ok &= y[0] == heaviside(p[0]) + heaviside(x[0]);
   //
   return ok;
}