Convert an ADFun Object to a Json AD Graph: Example and Test

to_json.cpp

@(@\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}} }@)@ This is cppad-20221105 documentation. Here is a link to its current documentation . Convert an ADFun Object to a Json AD Graph: Example and Test
Source Code


# include <cppad/cppad.hpp>

bool to_json(void)
{   bool ok = true;
    using CppAD::vector;
    using CppAD::AD;
    //
    // An AD graph example
    // node_1 : x[0]
    // node_2 : x[1]
    // node_3 : x[0] + x[1]
    // node_4 : (x[0] + x[1]) * x[1]
    // y[0]   = (x[0] + x[1]) * x[1]
    // use single quote to avoid having to escape double quote
    std::string json =
        "{\n"
        "   'function_name'  : 'to_json example',\n"
        "   'op_define_vec'  : [ 2, [\n"
        "       { 'op_code':1, 'name':'add', 'n_arg':2 } ,\n"
        "       { 'op_code':2, 'name':'mul', 'n_arg':2 } ]\n"
        "   ],\n"
        "   'n_dynamic_ind'  : 0,\n"
        "   'n_variable_ind' : 2,\n"
        "   'constant_vec'   : [ 0, [ ] ],\n"
        "   'op_usage_vec'   : [ 2, [\n"
        "       [ 1, 1, 2 ] ,\n"
        "       [ 2, 3, 2 ] ]\n"
        "   ],\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) = (x_0 + x_1) * x_1
    CppAD::ADFun< AD<double> > af;
    af.from_json(json);
    ok &= af.Domain() == 2;
    ok &= af.Range() == 1;
    //
    // Declare independent variables for a new recording
    vector< AD<double> > ax(2);
    ax[0] = 1.0;
    ax[1] = 2.0;
    CppAD::Independent(ax);
    //
    // Compute f(x)
    af.Forward(0, ax);
    //
    // Compute z = f'(x)
    vector< AD<double> > aw(1), az(2);
    aw[0] = 1.0;
    az    = af.Reverse(1, aw);
    //
    // define g(x) = f'(x)
    CppAD::ADFun<double> g(ax, az);
    // ------------------------------------------------------------------------
    // Convert to Json graph and back
    json = g.to_json();
    // std::cout << json;
    g.from_json(json);
    // ------------------------------------------------------------------------
    //
    // Evaluate function corresponding to g
    vector<double> x(2), z(2);
    x[0] = 3.0;
    x[1] = 4.0;
    z = g.Forward(0, x);
    //
    // should be derivative of f
    ok &= z[0] == x[1];
    ok &= z[1] == x[0] + 2.0 * x[1];
    //
    return ok;
}

Input File: example/json/to_json.cpp