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36 * \brief API for calculation of centers of mass/geometry.
38 * This header defines a few functions that can be used to calculate
39 * centers of mass/geometry for a group of atoms.
40 * These routines can be used independently of the other parts of the
41 * library, but they are also used internally by the selection engine.
42 * In most cases, it should not be necessary to call these functions
44 * Instead, one should write an analysis tool such that it gets all
45 * positions through selections.
47 * The functions in the header can be divided into a few groups based on the
48 * parameters they take. The simplest group of functions calculates the center
49 * of a single group of atoms:
50 * - gmx_calc_cog(): Calculates the center of geometry (COG) of a given
52 * - gmx_calc_com(): Calculates the center of mass (COM) of a given group
54 * - gmx_calc_comg(): Calculates either the COM or COG, based on a
57 * A second set of routines is provided for calculating the centers for groups
58 * that wrap over periodic boundaries (gmx_calc_cog_pbc(), gmx_calc_com_pbc(),
59 * gmx_calc_comg_pbc()). These functions are slower, because they need to
60 * adjust the center iteratively.
62 * It is also possible to calculate centers for several groups of atoms in
63 * one call. The functions gmx_calc_cog_block(), gmx_calc_com_block() and
64 * gmx_calc_comg_block() take an index group and a partitioning of that index
65 * group (as a \c t_block structure), and calculate the centers for
66 * each group defined by the \c t_block structure separately.
68 * Finally, there is a function gmx_calc_comg_blocka() that takes both the
69 * index group and the partitioning as a single \c t_blocka structure.
71 * \author Teemu Murtola <teemu.murtola@gmail.com>
72 * \ingroup module_selection
74 #ifndef GMX_SELECTION_CENTEROFMASS_H
75 #define GMX_SELECTION_CENTEROFMASS_H
77 #include "gromacs/math/vectypes.h"
85 * Calculate a single center of geometry.
87 * \param[in] top Topology structure (unused, can be NULL).
88 * \param[in] x Position vectors of all atoms.
89 * \param[in] nrefat Number of atoms in the index.
90 * \param[in] index Indices of atoms.
91 * \param[out] xout COG position for the indexed atoms.
93 void gmx_calc_cog(const gmx_mtop_t* top, rvec x[], int nrefat, const int index[], rvec xout);
94 /** Calculate a single center of mass. */
95 void gmx_calc_com(const gmx_mtop_t* top, rvec x[], int nrefat, const int index[], rvec xout);
96 /** Calculate force on a single center of geometry. */
97 void gmx_calc_cog_f(const gmx_mtop_t* top, rvec f[], int nrefat, const int index[], rvec fout);
99 * Calculate force on a single center of mass.
101 * \param[in] top Topology structure (unused, can be NULL).
102 * \param[in] f Forces on all atoms.
103 * \param[in] nrefat Number of atoms in the index.
104 * \param[in] index Indices of atoms.
105 * \param[out] fout Force on the COM position for the indexed atoms.
107 void gmx_calc_com_f(const gmx_mtop_t* top, rvec f[], int nrefat, const int index[], rvec fout);
108 /** Calculate a single center of mass/geometry. */
109 void gmx_calc_comg(const gmx_mtop_t* top, rvec x[], int nrefat, const int index[], bool bMass, rvec xout);
110 /** Calculate force on a single center of mass/geometry. */
111 void gmx_calc_comg_f(const gmx_mtop_t* top, rvec f[], int nrefat, const int index[], bool bMass, rvec fout);
113 /** Calculate a single center of geometry iteratively, taking PBC into account. */
114 void gmx_calc_cog_pbc(const gmx_mtop_t* top, rvec x[], const t_pbc* pbc, int nrefat, const int index[], rvec xout);
115 /** Calculate a single center of mass iteratively, taking PBC into account. */
116 void gmx_calc_com_pbc(const gmx_mtop_t* top, rvec x[], const t_pbc* pbc, int nrefat, const int index[], rvec xout);
117 /** Calculate a single center of mass/geometry iteratively with PBC. */
118 void gmx_calc_comg_pbc(const gmx_mtop_t* top,
127 * Calculate centers of geometry for a blocked index.
129 * \param[in] top Topology structure (unused, can be NULL).
130 * \param[in] x Position vectors of all atoms.
131 * \param[in] block t_block structure that divides \p index into blocks.
132 * \param[in] index Indices of atoms.
133 * \param[out] xout \p block->nr COG positions.
135 void gmx_calc_cog_block(const gmx_mtop_t* top, rvec x[], const t_block* block, const int index[], rvec xout[]);
136 /** Calculate centers of mass for a blocked index. */
137 void gmx_calc_com_block(const gmx_mtop_t* top, rvec x[], const t_block* block, const int index[], rvec xout[]);
138 /** Calculate forces on centers of geometry for a blocked index. */
139 void gmx_calc_cog_f_block(const gmx_mtop_t* top, rvec f[], const t_block* block, const int index[], rvec fout[]);
141 * Calculate forces on centers of mass for a blocked index.
143 * \param[in] top Topology structure (unused, can be NULL).
144 * \param[in] f Forces on all atoms.
145 * \param[in] block t_block structure that divides \p index into blocks.
146 * \param[in] index Indices of atoms.
147 * \param[out] fout \p block->nr Forces on COM positions.
149 void gmx_calc_com_f_block(const gmx_mtop_t* top, rvec f[], const t_block* block, const int index[], rvec fout[]);
150 /** Calculate centers of mass/geometry for a blocked index. */
151 void gmx_calc_comg_block(const gmx_mtop_t* top,
153 const t_block* block,
157 /** Calculate forces on centers of mass/geometry for a blocked index. */
158 void gmx_calc_comg_f_block(const gmx_mtop_t* top,
160 const t_block* block,
164 /** Calculate centers of mass/geometry for a set of blocks; */
165 void gmx_calc_comg_blocka(const gmx_mtop_t* top, rvec x[], const t_blocka* block, bool bMass, rvec xout[]);
166 /** Calculate forces on centers of mass/geometry for a set of blocks; */
167 void gmx_calc_comg_f_blocka(const gmx_mtop_t* top, rvec x[], const t_blocka* block, bool bMass, rvec xout[]);