1 #ifndef STAN_MATH_REV_FUN_DETERMINANT_HPP
2 #define STAN_MATH_REV_FUN_DETERMINANT_HPP
3 
4 #include <stan/math/rev/meta.hpp>
5 #include <stan/math/rev/core.hpp>
6 #include <stan/math/prim/err.hpp>
7 #include <stan/math/prim/fun/Eigen.hpp>
8 
9 namespace stan {
10 namespace math {
11 
12 template <typename T, require_rev_matrix_t<T>* = nullptr>
determinant(const T & m)13 inline var determinant(const T& m) {
14   check_square("determinant", "m", m);
15 
16   if (m.size() == 0) {
17     return var(1.0);
18   }
19 
20   arena_t<T> arena_m = m;
21   auto m_lu = arena_m.val().partialPivLu();
22   auto arena_m_inv_transpose = to_arena(m_lu.inverse().transpose());
23   var det = m_lu.determinant();
24 
25   reverse_pass_callback([arena_m, det, arena_m_inv_transpose]() mutable {
26     arena_m.adj() += (det.adj() * det.val()) * arena_m_inv_transpose;
27   });
28 
29   return det;
30 }
31 
32 }  // namespace math
33 }  // namespace stan
34 #endif
35