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00025 #ifndef EIGEN_DETERMINANT_H
00026 #define EIGEN_DETERMINANT_H
00027
00028 namespace Eigen {
00029
00030 namespace internal {
00031
00032 template<typename Derived>
00033 inline const typename Derived::Scalar bruteforce_det3_helper
00034 (const MatrixBase<Derived>& matrix, int a, int b, int c)
00035 {
00036 return matrix.coeff(0,a)
00037 * (matrix.coeff(1,b) * matrix.coeff(2,c) - matrix.coeff(1,c) * matrix.coeff(2,b));
00038 }
00039
00040 template<typename Derived>
00041 const typename Derived::Scalar bruteforce_det4_helper
00042 (const MatrixBase<Derived>& matrix, int j, int k, int m, int n)
00043 {
00044 return (matrix.coeff(j,0) * matrix.coeff(k,1) - matrix.coeff(k,0) * matrix.coeff(j,1))
00045 * (matrix.coeff(m,2) * matrix.coeff(n,3) - matrix.coeff(n,2) * matrix.coeff(m,3));
00046 }
00047
00048 template<typename Derived,
00049 int DeterminantType = Derived::RowsAtCompileTime
00050 > struct determinant_impl
00051 {
00052 static inline typename traits<Derived>::Scalar run(const Derived& m)
00053 {
00054 if(Derived::ColsAtCompileTime==Dynamic && m.rows()==0)
00055 return typename traits<Derived>::Scalar(1);
00056 return m.partialPivLu().determinant();
00057 }
00058 };
00059
00060 template<typename Derived> struct determinant_impl<Derived, 1>
00061 {
00062 static inline typename traits<Derived>::Scalar run(const Derived& m)
00063 {
00064 return m.coeff(0,0);
00065 }
00066 };
00067
00068 template<typename Derived> struct determinant_impl<Derived, 2>
00069 {
00070 static inline typename traits<Derived>::Scalar run(const Derived& m)
00071 {
00072 return m.coeff(0,0) * m.coeff(1,1) - m.coeff(1,0) * m.coeff(0,1);
00073 }
00074 };
00075
00076 template<typename Derived> struct determinant_impl<Derived, 3>
00077 {
00078 static inline typename traits<Derived>::Scalar run(const Derived& m)
00079 {
00080 return bruteforce_det3_helper(m,0,1,2)
00081 - bruteforce_det3_helper(m,1,0,2)
00082 + bruteforce_det3_helper(m,2,0,1);
00083 }
00084 };
00085
00086 template<typename Derived> struct determinant_impl<Derived, 4>
00087 {
00088 static typename traits<Derived>::Scalar run(const Derived& m)
00089 {
00090
00091 return bruteforce_det4_helper(m,0,1,2,3)
00092 - bruteforce_det4_helper(m,0,2,1,3)
00093 + bruteforce_det4_helper(m,0,3,1,2)
00094 + bruteforce_det4_helper(m,1,2,0,3)
00095 - bruteforce_det4_helper(m,1,3,0,2)
00096 + bruteforce_det4_helper(m,2,3,0,1);
00097 }
00098 };
00099
00100 }
00101
00106 template<typename Derived>
00107 inline typename internal::traits<Derived>::Scalar MatrixBase<Derived>::determinant() const
00108 {
00109 assert(rows() == cols());
00110 typedef typename internal::nested<Derived,Base::RowsAtCompileTime>::type Nested;
00111 return internal::determinant_impl<typename internal::remove_all<Nested>::type>::run(derived());
00112 }
00113
00114 }
00115
00116 #endif // EIGEN_DETERMINANT_H