force.h

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/*
 * Copyright (C) 2004-2005 by David J. Hardy.  All rights reserved.
 */

#ifndef FORCE_H
#define FORCE_H

#include "mdapi/mdtypes.h"

#ifdef __cplusplus
extern "C" {
#endif

  typedef struct ForceParam_tag {
    /* Force field parameters as defined by the MDAPI mdtypes.h file. */
    MD_AtomPrm *atomprm;   
    MD_BondPrm *bondprm;   
    MD_AnglePrm *angleprm; 
    MD_TorsPrm *dihedprm;  
    MD_TorsPrm *imprprm;   
    MD_NbfixPrm *nbfixprm; 
    int32 atomprm_len;     
    int32 bondprm_len;     
    int32 angleprm_len;    
    int32 dihedprm_len;    
    int32 imprprm_len;     
    int32 nbfixprm_len;    
    /* Topology parameters as defined by the MDAPI mdtypes.h file. */
    MD_Atom *atom;         
    MD_Bond *bond;         
    MD_Angle *angle;       
    MD_Tors *dihed;        
    MD_Tors *impr;         
    MD_Excl *excl;         
    int32 atom_len;        
    int32 bond_len;        
    int32 angle_len;       
    int32 dihed_len;       
    int32 impr_len;        
    int32 excl_len;        
    /* (semi-)periodic orthogonal cell size */
    double xlen;           
    double ylen;           
    double zlen;           
    MD_Dvec center;        
    /* boundary conditions defined around center */
    double radius1;        
    double radius2;        
    double length1;        
    double length2;        
    double konst1;         
    double konst2;         
    int32 exp1;            
    int32 exp2;            
    /* nonbonded parameters */
    double cutoff;         
    double elec_cutoff;    
    double vdw_cutoff;     
    double switchdist;     
    double elec_const;     
    double dielectric;     
    double scaling14;      
    /* flags */
    int32 flags;           
  } ForceParam;


  enum ForceFlags_tag {
    /* force types */
    FORCE_BOND        = 0x000001,
    FORCE_ANGLE       = 0x000002,
    FORCE_DIHED       = 0x000004,
    FORCE_IMPR        = 0x000008,
    FORCE_ELEC        = 0x000010,
    FORCE_VDW         = 0x000020,
    FORCE_BONDED      = FORCE_BOND | FORCE_ANGLE | FORCE_DIHED | FORCE_IMPR,
    FORCE_NONBONDED   = FORCE_ELEC | FORCE_VDW,
    FORCE_ALL         = FORCE_BONDED | FORCE_NONBONDED,
    FORCE_ELEC_DIRECT = 0x000040,
    FORCE_VDW_DIRECT  = 0x000080,
    FORCE_DIRECT      = FORCE_ELEC_DIRECT | FORCE_VDW_DIRECT,
    FORCE_MASK_TYPE   = 0x0000FF,
    /* periodicity */
    FORCE_NONPERIODIC = 0x000000,
    FORCE_X_PERIODIC  = 0x000100,
    FORCE_Y_PERIODIC  = 0x000200,
    FORCE_Z_PERIODIC  = 0x000400,
    FORCE_PERIODIC    = FORCE_X_PERIODIC | FORCE_Y_PERIODIC | FORCE_Z_PERIODIC,
    FORCE_MASK_PERIOD = 0x000F00,
    /* boundary restraints (for nonperiodic systems) */
    FORCE_SPHERE      = 0x001000,
    FORCE_X_CYLINDER  = 0x002000,
    FORCE_Y_CYLINDER  = 0x004000,
    FORCE_Z_CYLINDER  = 0x008000,
    FORCE_MASK_BC     = 0x00F000,
    /* nonbonded exclusion policy */
    FORCE_EXCL_NONE   = 0x000000,
    FORCE_EXCL_12     = 0x010000,
    FORCE_EXCL_13     = 0x020000,
    FORCE_EXCL_14     = 0x030000,
    FORCE_EXCL_SCAL14 = 0x040000,
    FORCE_MASK_EXCL   = 0x0F0000,
    /* nonbonded cutoff continuity and exclusions */
    FORCE_SMOOTH      = 0x100000,
    FORCE_SWITCH      = 0x200000,
    FORCE_CONTINUOUS  = FORCE_SMOOTH | FORCE_SWITCH,
    FORCE_ELEC_EXCL   = 0x400000,
    FORCE_VDW_EXCL    = 0x800000,
    FORCE_EXCL        = FORCE_ELEC_EXCL | FORCE_VDW_EXCL,
    FORCE_MASK_CUTOFF = 0xF00000,
    FORCE_MD_VACUUM   = FORCE_ALL | FORCE_EXCL_SCAL14 | FORCE_CONTINUOUS,
    FORCE_MD_CELL     = FORCE_MD_VACUUM | FORCE_PERIODIC
  };


  enum {
    FORCE_FAIL = -1  
  };


  typedef struct ForceEnergy_tag {
    double pe;     
    double bond;   
    double angle;  
    double dihed;  
    double impr;   
    double elec;   
    double vdw;    
    double bound;  
  } ForceEnergy;


  typedef struct ForceResult_tag {
    MD_Dvec *f;        
    MD_Dvec *f_bond;   
    MD_Dvec *f_angle;  
    MD_Dvec *f_dihed;  
    MD_Dvec *f_impr;   
    MD_Dvec *f_elec;   
    MD_Dvec *f_vdw;    
    MD_Dvec *f_bound;  
  } ForceResult;


  typedef struct ForceCell_tag {
    /* cells for geometric hashing, implement as cursor link list */
    int32 head;          /* index of first atom in this cell */
    int32 cnt;           /* count number of atoms in this cell */
    int32 nnbrs;         /* length of neighbor cell list */
    int32 nbr[14];       /* up to half-shell of neighbors, including self */
    MD_Dvec offset[14];  /* offset for neighbors that are periodic images */
  } ForceCell;


  typedef struct Force_tag {
    ForceParam *param;
    ForceEnergy *energy;
    ForceResult *result;

    double elec_const;
    double inv_elec_cutoff2;
    double switchdist2;
    double inv_denom_switch;
    double elec_cutoff2;
    double vdw_cutoff2;

    double *vdwtable;

    MD_Dvec lo;
    double inv_cutoff;
    double inv_xcellsize;
    double inv_ycellsize;
    double inv_zcellsize;

    MD_Dvec *wrap;

    int32 *next;
    ForceCell *cell;
    int32 ncells;
    int32 nxcells;
    int32 nycells;
    int32 nzcells;
    int32 is_resize;
    int32 is_xresize;
    int32 is_yresize;
    int32 is_zresize;

    /* nonbonded exclusion lists */
    int32 **excl_list;
    int32 **scaled14_list;

    /* helper arrays for building exclusion lists */
    int32 **exclx;     /* explicit exclusions (from MD_Excl) */
    int32 **excl12;    /* lists for 1-2 exclusions (from MD_Bond) */
    int32 **excl13;    /* lists for 1-3 exclusions */
    int32 **excl14;    /* lists for 1-4 exclusions */
    int32 **scaled14;  /* lists for scaled 1-4 exclusions */
    int32 *lenx;       /* counters for exclx lists */
    int32 *len12;      /* counters for excl12 lists */
    int32 *len13;      /* counters for excl13 lists */
    int32 *accum;      /* for merging lists */
    int32 *dest;       /* for merging lists */

    /* for boundary conditions */
    int32 is_bcterm1;
    int32 is_bcterm2;
    double sq_minradius;
    double minlength;

  } Force;


  /* force interface routines */

  int force_init(Force *);

  int force_setup(Force *, ForceParam *fp, ForceEnergy *fe, ForceResult *fr);

  int force_compute(Force *, const MD_Dvec *pos, MD_Dvec *wrap);

  void force_done(Force *);


  /* provide access to exclusion lists */

  int32 **force_excl_list(const Force *);

  int32 **force_scaled14_list(const Force *);


  /* setup subroutines */
  int force_setup_bonded(Force *);
  int force_setup_nonbonded(Force *);
  int force_setup_nonbonded_cells(Force *);
  int force_setup_boundary(Force *);

  /* compute subroutines */
  int force_compute_bonded(Force *, const MD_Dvec *pos);
  int force_compute_nonbonded(Force *, const MD_Dvec *pos, MD_Dvec *wrap);
  int force_compute_boundary(Force *, const MD_Dvec *pos, const MD_Dvec *wrap);


#ifdef __cplusplus
}
#endif

#endif /* FORCE_H */

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