src/gromacs/mdlib/groupcoord.h

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  37
  38 /*! \libinternal \file
  39  * \brief Assemble atomic positions of a (small) subset of atoms and distribute to all nodes.
  40  *
  41  *  This file contains functions to assemble the positions of a subset of the
  42  *  atoms and to do operations on it like determining the center of mass, or
  43  *  doing translations and rotations. These functions are useful when
  44  *  a subset of the positions needs to be compared to some set of reference
  45  *  positions, as e.g. done for essential dynamics.
  46  *
  47  * \inlibraryapi
  48  */
  49
  50 #include <stdio.h>
  51
  52 #include "gromacs/math/vectypes.h"
  53 #include "gromacs/utility/basedefinitions.h"
  54
  55 struct gmx_ga2la_t;
  56 struct t_commrec;
  57
  58 #ifdef __cplusplus
  59 extern "C" {
  60 #endif
  61
  62 /*! \brief Select local atoms of a group.
  63  *
  64  * Selects the indices of local atoms of a group and stores them in anrs_loc[0..nr_loc].
  65  * If you need the positions of the group's atoms on all nodes, provide a coll_ind[0..nr]
  66  * array and pass it on to communicate_group_positions. Thus the collective array
  67  * will always have the same atom order (ascending indices).
  68  *
  69  *  \param[in]     ga2la      Global to local atom index conversion data.
  70  *  \param[in]     nr         The total number of atoms that the group contains.
  71  *  \param[in]     anrs       The global atom number of the group's atoms.
  72  *  \param[out]    nr_loc     The number of group atoms present on the local node.
  73  *  \param[out]    anrs_loc   The local atom numbers of the group.
  74  *  \param[in,out] nalloc_loc Local allocation size of anrs_loc array.
  75  *  \param[out]    coll_ind   If not NULL this array must be of size nr. It stores
  76  *                            for each local atom where it belongs in the global
  77  *                            (collective) array such that it can be gmx_summed
  78  *                            in the communicate_group_positions routine.
  79  */
  80
  81 extern void dd_make_local_group_indices(gmx_ga2la_t *ga2la,
  82                                         const int nr, int anrs[], int *nr_loc,
  83                                         int *anrs_loc[], int *nalloc_loc,
  84                                         int coll_ind[]);
  85
  86
  87 /*! \brief Assemble local positions into a collective array present on all nodes.
  88  *
  89  * Communicate the positions of the group's atoms such that every node has all of
  90  * them. Unless running on huge number of cores, this is not a big performance impact
  91  * as long as the collective subset [0..nr] is kept small. The atom indices are
  92  * retrieved from anrs_loc[0..nr_loc]. If you call the routine for the serial case,
  93  * provide an array coll_ind[i] = i for i in 1..nr.
  94  *
  95  * If shifts != NULL, the PBC representation of each atom is chosen such that a
  96  * continuous trajectory results. Therefore, if the group is whole at the start
  97  * of the simulation, it will always stay whole.
  98  * If shifts = NULL, the group positions are not made whole again, but assembled
  99  * and distributed to all nodes. The variables marked "optional" are not used in
 100  * that case.
 101  *
 102  * \param[in]     cr           Pointer to MPI communication data.
 103  * \param[out]    xcoll        Collective array of positions, identical on all nodes
 104  *                             after this routine has been called.
 105  * \param[in,out] shifts       Collective array of shifts for xcoll, needed to make
 106  *                             the group whole. This array remembers the shifts
 107  *                             since the start of the simulation (where the group
 108  *                             is whole) and must therefore not be changed outside
 109  *                             of this routine! If NULL, the group will not be made
 110  *                             whole and the optional variables are ignored.
 111  * \param[out]    extra_shifts Extra shifts since last time step, only needed as
 112  *                             buffer variable [0..nr] (optional).
 113  * \param[in]     bNS          Neighbor searching / domain re-decomposition has been
 114  *                             performed at the begin of this time step such that
 115  *                             the shifts have changed and need to be updated
 116  *                             (optional).
 117  * \param[in]     x_loc        Pointer to the local atom positions this node has.
 118  * \param[in]     nr           Total number of atoms in the group.
 119  * \param[in]     nr_loc       Number of group atoms on the local node.
 120  * \param[in]     anrs_loc     Array of the local atom indices.
 121  * \param[in]     coll_ind     This array of size nr stores for each local atom where
 122  *                             it belongs in the collective array so that the local
 123  *                             contributions can be gmx_summed. It is provided by
 124  *                             dd_make_local_group_indices.
 125  * \param[in,out] xcoll_old    Positions from the last time step, used to make the
 126  *                             group whole (optional).
 127  * \param[in]     box          Simulation box matrix, needed to shift xcoll such that
 128  *                             the group becomes whole (optional).
 129  */
 130 extern void communicate_group_positions(t_commrec *cr, rvec *xcoll, ivec *shifts,
 131                                         ivec *extra_shifts, const gmx_bool bNS,
 132                                         rvec *x_loc, const int nr, const int nr_loc,
 133                                         int *anrs_loc, int *coll_ind, rvec *xcoll_old,
 134                                         matrix box);
 135
 136 /*! \brief Calculates the center of the positions x locally.
 137  *
 138  * Calculates the center of mass (if masses are given in the weight array) or
 139  * the geometrical center (if NULL is passed as weight).
 140  *
 141  * \param[in]   x            Positions.
 142  * \param[in]   weight       Can be NULL or an array of weights. If masses are
 143  *                           given as weights, the COM is calculated.
 144  * \param[in]   nr           Number of positions and weights if present.
 145  * \param[out]  center       The (weighted) center of the positions.
 146  *
 147  */
 148 extern void get_center(rvec x[], real weight[], const int nr, rvec center);
 149
 150
 151 /*! \brief Calculates the sum of the positions x locally.
 152  *
 153  * Calculates the (weighted) sum of position vectors and returns the sum of
 154  * weights, which is needed when local contributions shall be summed to a
 155  * global weighted center.
 156  *
 157  * \param[in]   x            Array of positions.
 158  * \param[in]   weight       Can be NULL or an array of weights.
 159  * \param[in]   nr           Number of positions and weights if present.
 160  * \param[out]  dsumvec      The (weighted) sum of the positions.
 161  * \return Sum of weights.
 162  *
 163  */
 164 extern double get_sum_of_positions(rvec x[], real weight[], const int nr, dvec dsumvec);
 165
 166
 167 /*! \brief Calculates the global center of all local arrays x.
 168  *
 169  * Get the center from local positions [0..nr_loc], this involves communication.
 170  * Not that the positions must already have the correct PBC representation. Use
 171  * this routine if no collective coordinates are assembled from which the center
 172  * could be calculated without communication.
 173  *
 174  * \param[in]   cr           Pointer to MPI communication data.
 175  * \param[in]   x_loc        Array of local positions [0..nr_loc].
 176  * \param[in]   weight_loc   Array of local weights, these are the masses if the
 177  *                           center of mass is to be calculated.
 178  * \param[in]   nr_loc       The number of positions on the local node.
 179  * \param[in]   nr_group     The number of positions in the whole group. Since
 180  *                           this is known anyway, we do not need to communicate
 181  *                           and sum nr_loc if we pass it over.
 182  * \param[out]  center       The (weighted) center of all x_loc from all the
 183  *                           nodes.
 184  */
 185 extern void get_center_comm(t_commrec *cr, rvec x_loc[], real weight_loc[],
 186                             int nr_loc, int nr_group, rvec center);
 187
 188
 189 /*! \brief Translate positions.
 190  *
 191  * Add a translation vector to the positions x.
 192  *
 193  * \param[in,out] x          Array of positions.
 194  * \param[in]     nr         Number of entries in the position array.
 195  * \param[in]     transvec   Translation vector to be added to all positions.
 196  *
 197  */
 198 extern void translate_x(rvec x[], const int nr, const rvec transvec);
 199
 200
 201 /*! \brief Rotate positions.
 202  *
 203  * Rotate the positions with the rotation matrix.
 204  *
 205  * \param[in,out] x          Array of positions.
 206  * \param[in]     nr         Number of entries in the position array.
 207  * \param[in]     rmat       Rotation matrix to operate on all positions.
 208  *
 209  */
 210 extern void rotate_x(rvec x[], const int nr, matrix rmat);
 211
 212 #ifdef __cplusplus
 213 }
 214 #endif