src/gromacs/math/matrix.h

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  35 /*! \libinternal
  36  * \file
  37  * \brief Declares special case of 3x3 matrix frequently used, and associated functions.
  38  *
  39  * \author Christian Blau <cblau@gwdg.de>
  40  * \ingroup module_math
  41  */
  42
  43 #ifndef GMX_MATH_MATRIX_H_
  44 #define GMX_MATH_MATRIX_H_
  45
  46 #include <array>
  47
  48 #include "gromacs/utility/real.h"
  49
  50 #include "multidimarray.h"
  51
  52 namespace gmx
  53 {
  54
  55 /*! \brief Three-by-three matrix of ElementType.
  56  * \tparam ElementType type of element to be stored in matrix
  57  */
  58 template <class ElementType>
  59 using BasicMatrix3x3 = MultiDimArray<std::array<ElementType, 3*3>, extents <3, 3> >;
  60
  61 /*! \brief Three-by-three real number matrix.
  62  * \note will replace the C-style real[3][3] "matrix"
  63  */
  64 using Matrix3x3          = BasicMatrix3x3<real>;
  65 //! Convenience alias for a matrix view
  66 using Matrix3x3Span      = Matrix3x3::view_type;
  67 //! Convenience alias for a const matrix view
  68 using Matrix3x3ConstSpan = Matrix3x3::const_view_type;
  69
  70 //! Determinant of a 3x3 matrix
  71 constexpr real determinant(Matrix3x3ConstSpan matrix)
  72 {
  73     return (  matrix(0, 0)*(matrix(1, 1)*matrix(2, 2)-matrix(2, 1)*matrix(1, 2))
  74               -matrix(1, 0)*(matrix(0, 1)*matrix(2, 2)-matrix(2, 1)*matrix(0, 2))
  75               +matrix(2, 0)*(matrix(0, 1)*matrix(1, 2)-matrix(1, 1)*matrix(0, 2)));
  76 }
  77
  78 //! Calculates the trace of a 3x3 matrix view
  79 constexpr real trace(Matrix3x3ConstSpan matrixView)
  80 {
  81     return matrixView(0, 0) + matrixView(1, 1) + matrixView(2, 2);
  82 }
  83 } // namespace gmx
  84
  85 #endif