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37 * \brief Structure and basic routines to handle periodic boundary conditions.
39 * This file contains CPU
41 * \todo CPU, GPU and SIMD routines essentially do the same operations on
42 * different data-types. Currently this leads to code duplication,
43 * which has to be resolved. For details, see Issue #2863
44 * https://gitlab.com/gromacs/gromacs/-/issues/2863
46 * \author Mark Abraham <mark.j.abraham@gmail.com>
47 * \author Berk Hess <hess@kth.se>
48 * \author Artem Zhmurov <zhmurov@gmail.com>
51 * \ingroup module_pbcutil
53 #ifndef GMX_PBCUTIL_PBC_AIUC_H
54 #define GMX_PBCUTIL_PBC_AIUC_H
56 #include "gromacs/pbcutil/ishift.h"
58 /*! \brief Compact and ordered version of the PBC matrix.
60 * The structure contains all the dimensions of the periodic box,
61 * arranged so that the memory access pattern is more efficient.
62 * This duplicates the information, stored in PBC 'box' matrix object,
63 * but without duplicating off-diagonal members of the matrix.
64 * The structure can be set by setPbcAiuc( ... ) routine below.
88 /*! \brief Set the PBC data-structure.
90 * \param[in] numPbcDim Number of periodic dimensions:
92 * 1 - periodicity along X-axis.
93 * 2 - periodicity in XY plane.
94 * 3 - periodicity along all dimensions.
95 * \param[in] box Matrix, describing the periodic cell.
96 * \param[out] pbcAiuc Pointer to PbcAiuc structure to be initialized.
99 static inline void setPbcAiuc(int numPbcDim, const matrix box, PbcAiuc* pbcAiuc)
102 pbcAiuc->invBoxDiagZ = 0.0f;
103 pbcAiuc->boxZX = 0.0f;
104 pbcAiuc->boxZY = 0.0f;
105 pbcAiuc->boxZZ = 0.0f;
106 pbcAiuc->invBoxDiagY = 0.0f;
107 pbcAiuc->boxYX = 0.0f;
108 pbcAiuc->boxYY = 0.0f;
109 pbcAiuc->invBoxDiagX = 0.0f;
110 pbcAiuc->boxXX = 0.0f;
114 pbcAiuc->invBoxDiagZ = 1.0f / box[ZZ][ZZ];
115 pbcAiuc->boxZX = box[ZZ][XX];
116 pbcAiuc->boxZY = box[ZZ][YY];
117 pbcAiuc->boxZZ = box[ZZ][ZZ];
121 pbcAiuc->invBoxDiagY = 1.0f / box[YY][YY];
122 pbcAiuc->boxYX = box[YY][XX];
123 pbcAiuc->boxYY = box[YY][YY];
127 pbcAiuc->invBoxDiagX = 1.0f / box[XX][XX];
128 pbcAiuc->boxXX = box[XX][XX];
132 /*! \brief Computes the vector between two points taking PBC into account.
134 * Computes the vector dr between points r2 and r1, taking into account the
135 * periodic boundary conditions, described in pbcAiuc object. Note that this
136 * routine always does the PBC arithmetic for all directions, multiplying the
137 * displacements by zeroes if the corresponding direction is not periodic.
138 * For triclinic boxes only distances up to half the smallest box diagonal
139 * element are guaranteed to be the shortest. This means that distances from
140 * 0.5/sqrt(2) times a box vector length (e.g. for a rhombic dodecahedron)
141 * can use a more distant periodic image.
143 * \todo This routine operates on rvec types and uses PbcAiuc to define
144 * periodic box, but essentially does the same thing as SIMD and GPU
145 * version. These will have to be unified in future to avoid code
146 * duplication. See Issue #2863:
147 * https://gitlab.com/gromacs/gromacs/-/issues/2863
149 * \param[in] pbcAiuc PBC object.
150 * \param[in] r1 Coordinates of the first point.
151 * \param[in] r2 Coordinates of the second point.
152 * \param[out] dr Resulting distance.
154 static inline void pbcDxAiuc(const PbcAiuc& pbcAiuc, const rvec& r1, const rvec& r2, rvec dr)
156 dr[XX] = r1[XX] - r2[XX];
157 dr[YY] = r1[YY] - r2[YY];
158 dr[ZZ] = r1[ZZ] - r2[ZZ];
160 float shz = rintf(dr[ZZ] * pbcAiuc.invBoxDiagZ);
161 dr[XX] -= shz * pbcAiuc.boxZX;
162 dr[YY] -= shz * pbcAiuc.boxZY;
163 dr[ZZ] -= shz * pbcAiuc.boxZZ;
165 float shy = rintf(dr[YY] * pbcAiuc.invBoxDiagY);
166 dr[XX] -= shy * pbcAiuc.boxYX;
167 dr[YY] -= shy * pbcAiuc.boxYY;
169 float shx = rintf(dr[XX] * pbcAiuc.invBoxDiagX);
170 dr[XX] -= shx * pbcAiuc.boxXX;
174 #endif // GMX_PBCUTIL_PBC_AIUC_H