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

graph_comp_op.cpp

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C++ AD Graph Comparison Operators: Example and Test

Source Code

# include <cppad/cppad.hpp>

bool comp_op(void)
{  bool ok = true;
   using std::string;
   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] )
   //
   // 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("comp_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);
   //
   // x[0] < p[0]
   op_enum = CppAD::graph::comp_lt_graph_op;
   graph_obj.operator_vec_push_back(op_enum);
   graph_obj.operator_arg_push_back(2);
   graph_obj.operator_arg_push_back(1);
   //
   // node_3 : p[0] - x[0]
   op_enum = CppAD::graph::sub_graph_op;
   graph_obj.operator_vec_push_back(op_enum);
   graph_obj.operator_arg_push_back(1);
   graph_obj.operator_arg_push_back(2);
   //
   // node_4 : log( p[0] - x[0] )
   op_enum = CppAD::graph::log_graph_op;
   graph_obj.operator_vec_push_back(op_enum);
   graph_obj.operator_arg_push_back(3);
   //
   // y[0]   = log( p[0] - x[0] )
   graph_obj.dependent_vec_push_back(4);
   //
   // f(x, p) = log( p[0] - 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] = 0.3;
   x[0] = 0.2;
   //
   // compute y = f(x, p)
   f.new_dynamic(p);
   CPPAD_TESTVECTOR(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 Graph graph and back again
   f.to_graph(graph_obj);
   // std::cout << graph;
   f.from_graph(graph_obj);
   // -----------------------------------------------------------------------
   //
   // 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;
}