$\newcommand{\W}[1]{ \; #1 \; } \newcommand{\R}[1]{ {\rm #1} } \newcommand{\B}[1]{ {\bf #1} } \newcommand{\D}[2]{ \frac{\partial #1}{\partial #2} } \newcommand{\DD}[3]{ \frac{\partial^2 #1}{\partial #2 \partial #3} } \newcommand{\Dpow}[2]{ \frac{\partial^{#1}}{\partial {#2}^{#1}} } \newcommand{\dpow}[2]{ \frac{ {\rm d}^{#1}}{{\rm d}\, {#2}^{#1}} }$
 # include <cppad/cppad.hpp> # include <cppad/speed/det_by_lu.hpp> bool det_by_lu() { bool ok = true; double eps99 = 99.0 * std::numeric_limits<double>::epsilon(); // dimension of the matrix size_t n = 3; // construct the determinat object CppAD::det_by_lu<double> Det(n); double a[] = { 1., 2., 3., // a[0] a[1] a[2] 3., 2., 1., // a[3] a[4] a[5] 2., 1., 2. // a[6] a[7] a[8] }; CPPAD_TESTVECTOR(double) A(9); size_t i; for(i = 0; i < 9; i++) A[i] = a[i]; // evaluate the determinant double det = Det(A); double check; check = a[0]*(a[4]*a[8] - a[5]*a[7]) - a[1]*(a[3]*a[8] - a[5]*a[6]) + a[2]*(a[3]*a[7] - a[4]*a[6]); ok = CppAD::NearEqual(det, check, eps99, eps99); return ok; }