/* ----------------------------------------------------------------------
   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
   http://lammps.sandia.gov, Sandia National Laboratories
   Steve Plimpton, sjplimp@sandia.gov

   Copyright (2003) Sandia Corporation.  Under the terms of Contract
   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
   certain rights in this software.  This software is distributed under
   the GNU General Public License.

   See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */

#ifdef FIX_CLASS

FixStyle(srd,FixSRD)

#else

#ifndef LMP_FIX_SRD_H
#define LMP_FIX_SRD_H

#include "fix.h"

namespace LAMMPS_NS {

class FixSRD : public Fix {
 public:
  FixSRD(class LAMMPS *, int, char **);
  ~FixSRD();
  int setmask();
  void init();
  void setup(int);
  void pre_neighbor();
  void post_force(int);
  double compute_vector(int);

  double memory_usage();
  int pack_reverse_comm(int, int, double *);
  void unpack_reverse_comm(int, int *, double *);

 private:
  int me,nprocs;
  int bigexist,biggroup,biggroupbit;
  int collidestyle,lamdaflag,overlap,insideflag,exactflag,maxbounceallow;
  int cubicflag,shiftuser,shiftseed,shiftflag,tstat;
  int rescale_rotate,rescale_collide;
  double gridsrd,gridsearch,lamda,radfactor,cubictol;
  int triclinic,change_size,change_shape,deformflag;

  double dt_big,dt_srd;
  double mass_big,mass_srd;
  double temperature_srd;
  double sigma;
  double srd_per_cell;
  double dmax,vmax,vmaxsq;
  double maxbigdiam,minbigdiam;
  double dist_ghost,dist_srd,dist_srd_reneigh;   // explained in code

  int wallexist,nwall,wallvarflag;
  class FixWallSRD *wallfix;
  int *wallwhich;
  double *xwall,*xwallhold,*vwall;
  double **fwall;
  double walltrigger;

  class AtomVecEllipsoid *avec_ellipsoid;
  class AtomVecLine *avec_line;
  class AtomVecTri *avec_tri;

  // for orthogonal box, these are in box units
  // for triclinic box, these are in lamda units

  double srdlo[3],srdhi[3];                  // SRDs must stay inside
  double srdlo_reneigh[3],srdhi_reneigh[3];  // SRDs trigger a reneigh

  int dimension;
  int initflag,setupflag,reneighflag;
  class RanMars *random;
  class RanPark *randomshift;

  // stats

  int ncheck,ncollide,ninside,nrescale,reneighcount;
  int nbounce,bouncemaxnum,bouncemax;
  int stats_flag;
  int srd_bin_count;
  double srd_bin_temp;
  double stats[12],stats_all[12];

  double **flocal;       // local ptrs to atom force and torque
  double **tlocal;

  // info to store for each owned and ghost big particle and wall

  struct Big {
    int index;                 // local index of particle/wall
    int type;                  // SPHERE or ELLIPSOID or LINE or TRI or WALL
    double radius,radsq;       // radius of sphere
    double aradsqinv;          // 3 ellipsoid radii
    double bradsqinv;
    double cradsqinv;
    double length;             // length of line segment
    double normbody[3];        // normal of tri in body-frame
    double cutbinsq;           // add big to bin if within this distance
    double omega[3];           // current omega for sphere/ellipsoid/tri/line
    double ex[3],ey[3],ez[3];  // current orientation vecs for ellipsoid/tri
    double norm[3];            // current unit normal of tri in space-frame
    double theta;              // current orientation of line
  };

  Big *biglist;           // list of info for each owned & ghost big and wall
  int torqueflag;         // 1 if any big particle is torqued

  // current size of particle-based arrays

  int nbig;               // # of owned/ghost big particles and walls
  int maxbig;             // max number of owned/ghost big particles and walls
  int nmax;               // max number of SRD particles

  // bins for SRD velocity remap, shifting and communication
  // binsize and inv are in lamda units for triclinic

  int nbins1,nbin1x,nbin1y,nbin1z;
  double binsize1x,binsize1y,binsize1z;
  double bininv1x,bininv1y,bininv1z;

  struct BinAve {
    int owner;           // 1 if I am owner of this bin, 0 if not
    int n;               // # of SRD particles in bin
    double xctr[3];      // center point of bin, only used for triclinic
    double vsum[3];      // sum of v components for SRD particles in bin
    double random;       // random value if I am owner
  };

  struct BinComm {
    int nsend,nrecv;            // # of bins to send/recv
    int sendproc,recvproc;      // who to send/recv to/from
    int *sendlist,*recvlist;    // list of bins to send/recv
  };

  struct BinShift {
    int commflag;                 // 1 if this shift requires any comm
    int nbins,nbinx,nbiny,nbinz;  // extent of my bins
    int maxbinsq,maxvbin;
    int binlo[3],binhi[3];        // extent of my bins in global array
    double corner[3];             // lower,left corner to offset from
                                  // corner is in lamda units for triclinic
    BinAve *vbin;                 // my bins
    BinComm bcomm[6];             // bin communication pattern for overlaps
  };
  BinShift shifts[2];             // 0 = no shift, 1 = shift

  int maxbin1;
  int *binhead;          // 1st SRD particle in each bin
  int *binnext;          // next SRD particle in same bin
  int maxbuf;
  double *sbuf1,*sbuf2;  // buffers for send/recv of velocity bin data
  double *rbuf1,*rbuf2;

  // bins and stencil for collision searching for SRDs & big particles

  int nbins2,nbin2x,nbin2y,nbin2z;
  int maxbin2;
  double binsize2x,binsize2y,binsize2z;
  double bininv2x,bininv2y,bininv2z;
  double xblo2,yblo2,zblo2;

  int *nbinbig;          // # of big particles overlapping each bin
  int **binbig;          // indices of big particles overlapping each bin
  int *binsrd;           // which bin each SRD particle is in
  int nstencil;          // # of bins in stencil
  int maxstencil;        // max # of bins stencil array can hold
  int **stencil;         // list of 3d bin offsets a big particle can overlap

  // persistent data for line/tri collision calculations

  double tfraction,theta0,theta1;
  double xs0[3],xs1[3],xsc[3];
  double xb0[3],xb1[3],xbc[3];
  double nbc[3];

  // shared data for triangle collision calculations

  // private functions

  void reset_velocities();
  void vbin_comm(int);
  void vbin_pack(BinAve *, int, int *, double *);
  void vbin_unpack(double *, BinAve *, int, int *);

  void collisions_single();
  void collisions_multi();

  int inside_sphere(double *, double *, Big *);
  int inside_ellipsoid(double *, double *, Big *);
  int inside_line(double *, double *, double *, double *, Big *, double);
  int inside_tri(double *, double *, double *, double *, Big *, double);
  int inside_wall(double *, int);

  double collision_sphere_exact(double *, double *, double *, double *,
                                Big *, double *, double *, double *);
  void collision_sphere_inexact(double *, double *,
                                Big *, double *, double *, double *);
  double collision_ellipsoid_exact(double *, double *, double *, double *,
                                   Big *, double *, double *, double *);
  void collision_ellipsoid_inexact(double *, double *,
                                   Big *, double *, double *, double *);
  double collision_line_exact(double *, double *, double *, double *,
                              Big *, double, double *, double *, double *);
  double collision_tri_exact(double *, double *, double *, double *,
                             Big *, double, double *, double *, double *);
  double collision_wall_exact(double *, int, double *,
                              double *, double *, double *);
  void collision_wall_inexact(double *, int, double *, double *, double *);

  void slip(double *, double *, double *, Big *,
            double *, double *,  double *);
  void slip_wall(double *, int, double *, double *);
  void noslip(double *, double *, double *, Big *, int,
              double *, double *,  double *);

  void force_torque(double *, double *, double *,
                    double *, double *,  double *);
  void force_wall(double *, double *, int);

  int update_srd(int, double, double *, double *, double *, double *);

  void parameterize();
  void setup_bounds();
  void setup_velocity_bins();
  void setup_velocity_shift(int, int);
  void setup_search_bins();
  void setup_search_stencil();
  void big_static();
  void big_dynamic();

  double point_bin_distance(double *, int, int, int);
  double bin_bin_distance(int, int, int);
  void velocity_stats(int);

  double newton_raphson(double, double);
  void lineside(double, double &, double &);
  void triside(double, double &, double &);

  double distance(int, int);
  void print_collision(int, int, int, double, double,
                       double *, double *, double *, int);
};

}

#endif
#endif

/* ERROR/WARNING messages:

E: Illegal ... command

Self-explanatory.  Check the input script syntax and compare to the
documentation for the command.  You can use -echo screen as a
command-line option when running LAMMPS to see the offending line.

E: Could not find fix srd group ID

Self-explanatory.

E: Fix srd requires newton pair on

Self-explanatory.

E: Fix srd requires ghost atoms store velocity

Use the communicate vel yes command to enable this.

E: Fix SRD no-slip requires atom attribute torque

This is because the SRD collisions will impart torque to the solute
particles.

E: Cannot change timestep once fix srd is setup

This is because various SRD properties depend on the timestep
size.

E: Cannot use fix wall/srd more than once

Nor is their a need to since multiple walls can be specified
in one command.

W: Fix SRD walls overlap but fix srd overlap not set

You likely want to set this in your input script.

E: Using fix srd with inconsistent fix deform remap option

When shearing the box in an SRD simulation, the remap v option for fix
deform needs to be used.

W: Using fix srd with box deformation but no SRD thermostat

The deformation will heat the SRD particles so this can
be dangerous.

W: Fix srd SRD moves may trigger frequent reneighboring

This is because the SRD particles may move long distances.

E: Fix SRD: bad search bin assignment

Something has gone wrong in your SRD model; try using more
conservative settings.

E: Fix SRD: bad stencil bin for big particle

Something has gone wrong in your SRD model; try using more
conservative settings.

E: Fix SRD: too many big particles in bin

Reset the ATOMPERBIN parameter at the top of fix_srd.cpp
to a larger value, and re-compile the code.

E: Fix SRD: too many walls in bin

This should not happen unless your system has been setup incorrectly.

E: Fix SRD: bad bin assignment for SRD advection

Something has gone wrong in your SRD model; try using more
conservative settings.

E: SRD particle %d started inside big particle %d on step %ld bounce %d

See the inside keyword if you want this message to be an error vs
warning.

W: SRD particle %d started inside big particle %d on step %ld bounce %d

See the inside keyword if you want this message to be an error vs
warning.

E: Bad quadratic solve for particle/line collision

This is an internal error.  It should nornally not occur.

E: Bad quadratic solve for particle/tri collision

This is an internal error.  It should nornally not occur.

W: Fix srd particle moved outside valid domain

This may indicate a problem with your simulation parameters.

E: Big particle in fix srd cannot be point particle

Big particles must be extended spheriods or ellipsoids.

E: Cannot use lines with fix srd unless overlap is set

This is because line segements are connected to each other.

E: Cannot use tris with fix srd unless overlap is set

This is because triangles are connected to each other.

E: Fix srd requires SRD particles all have same mass

Self-explanatory.

E: Fewer SRD bins than processors in some dimension

This is not allowed.  Make your SRD bin size smaller.

E: SRD bins for fix srd are not cubic enough

The bin shape is not within tolerance of cubic.  See the cubic
keyword if you want this message to be an error vs warning.

W: SRD bins for fix srd are not cubic enough

The bin shape is not within tolerance of cubic.  See the cubic
keyword if you want this message to be an error vs warning.

E: SRD bin size for fix srd differs from user request

Fix SRD had to adjust the bin size to fit the simulation box.  See the
cubic keyword if you want this message to be an error vs warning.

W: SRD bin size for fix srd differs from user request

Fix SRD had to adjust the bin size to fit the simulation box.  See the
cubic keyword if you want this message to be an error vs warning.

E: Fix srd lamda must be >= 0.6 of SRD grid size

This is a requirement for accuracy reasons.

W: SRD bin shifting turned on due to small lamda

This is done to try to preserve accuracy.

W: Fix srd grid size > 1/4 of big particle diameter

This may cause accuracy problems.

W: Fix srd viscosity < 0.0 due to low SRD density

This may cause accuracy problems.

W: Fix srd particles may move > big particle diameter

This may cause accuracy problems.

*/
