76 lines
2.2 KiB
C++
76 lines
2.2 KiB
C++
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#ifndef BOOST_QVM_DETAIL_DETERMINANT_IMPL_HPP_INCLUDED
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#define BOOST_QVM_DETAIL_DETERMINANT_IMPL_HPP_INCLUDED
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// Copyright 2008-2022 Emil Dotchevski and Reverge Studios, Inc.
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#include <boost/qvm/config.hpp>
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#include <boost/qvm/mat_traits_array.hpp>
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#include <boost/qvm/static_assert.hpp>
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namespace boost { namespace qvm {
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namespace
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qvm_detail
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{
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template <int N>
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struct
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det_size
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{
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};
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template <class M>
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BOOST_QVM_CONSTEXPR BOOST_QVM_INLINE_TRIVIAL
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typename mat_traits<M>::scalar_type
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determinant_impl_( M const & a, det_size<2> )
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{
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return
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mat_traits<M>::template read_element<0,0>(a) * mat_traits<M>::template read_element<1,1>(a) -
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mat_traits<M>::template read_element<1,0>(a) * mat_traits<M>::template read_element<0,1>(a);
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}
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template <class M,int N>
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BOOST_QVM_CONSTEXPR BOOST_QVM_INLINE_RECURSION
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typename mat_traits<M>::scalar_type
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determinant_impl_( M const & a, det_size<N> )
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{
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typedef typename mat_traits<M>::scalar_type T;
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T m[N-1][N-1];
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T det=T(0);
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for( int j1=0; j1!=N; ++j1 )
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{
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for( int i=1; i!=N; ++i )
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{
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int j2 = 0;
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for( int j=0; j!=N; ++j )
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{
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if( j==j1 )
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continue;
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m[i-1][j2] = mat_traits<M>::read_element_idx(i,j,a);
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++j2;
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}
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}
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T d=determinant_impl_(m,det_size<N-1>());
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if( j1&1 )
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d=-d;
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det += mat_traits<M>::read_element_idx(0,j1,a) * d;
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}
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return det;
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}
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template <class M>
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BOOST_QVM_CONSTEXPR BOOST_QVM_INLINE_TRIVIAL
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typename mat_traits<M>::scalar_type
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determinant_impl( M const & a )
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{
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BOOST_QVM_STATIC_ASSERT(mat_traits<M>::rows==mat_traits<M>::cols);
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return determinant_impl_(a,det_size<mat_traits<M>::rows>());
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}
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}
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} }
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#endif
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