1#ifndef BOOST_QVM_DETAIL_DETERMINANT_IMPL_HPP_INCLUDED
2#define BOOST_QVM_DETAIL_DETERMINANT_IMPL_HPP_INCLUDED
3
4// Copyright 2008-2022 Emil Dotchevski and Reverge Studios, Inc.
5
6// Distributed under the Boost Software License, Version 1.0. (See accompanying
7// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
8
9#include <boost/qvm/config.hpp>
10#include <boost/qvm/mat_traits_array.hpp>
11#include <boost/qvm/static_assert.hpp>
12
13namespace boost { namespace qvm {
14
15namespace
16qvm_detail
17 {
18 template <int N>
19 struct
20 det_size
21 {
22 };
23
24 template <class M>
25 BOOST_QVM_CONSTEXPR BOOST_QVM_INLINE_TRIVIAL
26 typename mat_traits<M>::scalar_type
27 determinant_impl_( M const & a, det_size<2> )
28 {
29 return
30 mat_traits<M>::template read_element<0,0>(a) * mat_traits<M>::template read_element<1,1>(a) -
31 mat_traits<M>::template read_element<1,0>(a) * mat_traits<M>::template read_element<0,1>(a);
32 }
33
34 template <class M,int N>
35 BOOST_QVM_CONSTEXPR BOOST_QVM_INLINE_RECURSION
36 typename mat_traits<M>::scalar_type
37 determinant_impl_( M const & a, det_size<N> )
38 {
39 typedef typename mat_traits<M>::scalar_type T;
40 T m[N-1][N-1];
41 T det=T(0);
42 for( int j1=0; j1!=N; ++j1 )
43 {
44 for( int i=1; i!=N; ++i )
45 {
46 int j2 = 0;
47 for( int j=0; j!=N; ++j )
48 {
49 if( j==j1 )
50 continue;
51 m[i-1][j2] = mat_traits<M>::read_element_idx(i,j,a);
52 ++j2;
53 }
54 }
55 T d=determinant_impl_(m,det_size<N-1>());
56 if( j1&1 )
57 d=-d;
58 det += mat_traits<M>::read_element_idx(0,j1,a) * d;
59 }
60 return det;
61 }
62
63 template <class M>
64 BOOST_QVM_CONSTEXPR BOOST_QVM_INLINE_TRIVIAL
65 typename mat_traits<M>::scalar_type
66 determinant_impl( M const & a )
67 {
68 BOOST_QVM_STATIC_ASSERT(mat_traits<M>::rows==mat_traits<M>::cols);
69 return determinant_impl_(a,det_size<mat_traits<M>::rows>());
70 }
71 }
72
73} }
74
75#endif
76

source code of boost/libs/qvm/include/boost/qvm/detail/determinant_impl.hpp