AD Unary Minus Operator: Example and Test

unary_minus.cpp

Headings

@(@\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 . AD Unary Minus Operator: Example and Test


# include <cppad/cppad.hpp>

bool UnaryMinus(void)
{   bool ok = true;
    using CppAD::AD;


    // domain space vector
    size_t n = 1;
    CPPAD_TESTVECTOR(AD<double>) x(n);
    x[0]      = 3.;

    // declare independent variables and start tape recording
    CppAD::Independent(x);

    // range space vector
    size_t m = 1;
    CPPAD_TESTVECTOR(AD<double>) y(m);
    y[0] = - x[0];

    // create f: x -> y and stop tape recording
    CppAD::ADFun<double> f(x, y);

    // check values
    ok &= ( y[0] == -3. );

    // forward computation of partials w.r.t. x[0]
    CPPAD_TESTVECTOR(double) dx(n);
    CPPAD_TESTVECTOR(double) dy(m);
    size_t p = 1;
    dx[0]    = 1.;
    dy       = f.Forward(p, dx);
    ok      &= ( dy[0] == -1. );   // dy[0] / dx[0]

    // reverse computation of dertivative of y[0]
    CPPAD_TESTVECTOR(double)  w(m);
    CPPAD_TESTVECTOR(double) dw(n);
    w[0] = 1.;
    dw   = f.Reverse(p, w);
    ok &= ( dw[0] == -1. );       // dy[0] / dx[0]

    // use a VecAD<Base>::reference object with unary minus
    CppAD::VecAD<double> v(1);
    AD<double> zero(0);
    v[zero] = x[0];
    AD<double> result = - v[zero];
    ok     &= (result == y[0]);

    return ok;
}

Input File: example/general/unary_minus.cpp