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/math/vec.h"
  49 #include "gromacs/utility/real.h"
  50
  51 #include "multidimarray.h"
  52
  53 namespace gmx
  54 {
  55
  56 /*! \brief Three-by-three matrix of ElementType.
  57  * \tparam ElementType type of element to be stored in matrix
  58  */
  59 template <class ElementType>
  60 using BasicMatrix3x3 = MultiDimArray<std::array<ElementType, 3*3>, extents <3, 3> >;
  61
  62 /*! \brief Three-by-three real number matrix.
  63  * \note will replace the C-style real[3][3] "matrix"
  64  */
  65 using Matrix3x3          = BasicMatrix3x3<real>;
  66 //! Convenience alias for a matrix view
  67 using Matrix3x3Span      = Matrix3x3::view_type;
  68 //! Convenience alias for a const matrix view
  69 using Matrix3x3ConstSpan = Matrix3x3::const_view_type;
  70
  71 //! Determinant of a 3x3 matrix
  72 constexpr real determinant(Matrix3x3ConstSpan matrix)
  73 {
  74     return (  matrix(0, 0)*(matrix(1, 1)*matrix(2, 2)-matrix(2, 1)*matrix(1, 2))
  75               -matrix(1, 0)*(matrix(0, 1)*matrix(2, 2)-matrix(2, 1)*matrix(0, 2))
  76               +matrix(2, 0)*(matrix(0, 1)*matrix(1, 2)-matrix(1, 1)*matrix(0, 2)));
  77 }
  78
  79 //! Calculates the trace of a 3x3 matrix view
  80 constexpr real trace(Matrix3x3ConstSpan matrixView)
  81 {
  82     return matrixView(0, 0) + matrixView(1, 1) + matrixView(2, 2);
  83 }
  84
  85 //! Calculate the transpose of a 3x3 matrix, from its view
  86 static Matrix3x3 transpose(Matrix3x3ConstSpan matrixView)
  87 {
  88
  89     return Matrix3x3({matrixView(0, 0), matrixView(1, 0), matrixView(2, 0),
  90                       matrixView(0, 1), matrixView(1, 1), matrixView(2, 1),
  91                       matrixView(0, 2), matrixView(1, 2), matrixView(2, 2)});
  92 }
  93
  94 //! Create new matrix type from legacy type.
  95 static Matrix3x3 createMatrix3x3FromLegacyMatrix(const matrix legacyMatrix)
  96 {
  97     GMX_RELEASE_ASSERT(legacyMatrix, "Legacy matrix needs to be non nullptr");
  98     Matrix3x3 newMatrix;
  99     for (int i = 0; i < DIM; i++)
 100     {
 101         for (int j = 0; j < DIM; j++)
 102         {
 103             newMatrix(i, j) = legacyMatrix[i][j];
 104         }
 105     }
 106     return newMatrix;
 107 }
 108
 109 } // namespace gmx
 110
 111 #endif