/* ----------------------------------------------------------------------
   LIGGGHTS - LAMMPS Improved for General Granular and Granular Heat
   Transfer Simulations

   LIGGGHTS is part of the CFDEMproject
   www.liggghts.com | www.cfdem.com

   This file was modified with respect to the release in LAMMPS
   Modifications are Copyright 2009-2012 JKU Linz
                     Copyright 2012-     DCS Computing GmbH, Linz

   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 directory.
------------------------------------------------------------------------- */

#include "math.h"
#include "stdio.h"
#include "stdlib.h"
#include "string.h"
#include "fix_rigid.h"
#include "math_extra.h"
#include "atom.h"
#include "atom_vec_ellipsoid.h"
#include "atom_vec_line.h"
#include "atom_vec_tri.h"
#include "domain.h"
#include "update.h"
#include "respa.h"
#include "modify.h"
#include "group.h"
#include "comm.h"
#include "random_mars.h"
#include "force.h"
#include "output.h"
#include "math_const.h"
#include "memory.h"
#include "error.h"

using namespace LAMMPS_NS;
using namespace FixConst;
using namespace MathConst;

enum{SINGLE,MOLECULE,GROUP};
enum{NONE,XYZ,XY,YZ,XZ};
enum{ISO,ANISO,TRICLINIC};

#define MAXLINE 256
#define CHUNK 1024
#define ATTRIBUTE_PERBODY 11

#define TOLERANCE 1.0e-6
#define EPSILON 1.0e-7

#define SINERTIA 0.4            // moment of inertia prefactor for sphere
#define EINERTIA 0.4            // moment of inertia prefactor for ellipsoid
#define LINERTIA (1.0/12.0)     // moment of inertia prefactor for line segment

/* ---------------------------------------------------------------------- */

FixRigid::FixRigid(LAMMPS *lmp, int narg, char **arg) :
  Fix(lmp, narg, arg)
{
  //not working correctly for 2d
  if(domain->dimension == 2) error->warning(FLERR,"Fix rigid should not be used for 2d simulations - inertia is for 3d systems");

  if (narg > 3 && strcmp(arg[3],"pseudo") == 0) return; //NP modified C.K.

  int i,ibody;

  scalar_flag = 1;
  extscalar = 0;
  time_integrate = 1;
  rigid_flag = 1;
  virial_flag = 1;
  create_attribute = 1;

  MPI_Comm_rank(world,&me);
  MPI_Comm_size(world,&nprocs);

  just_created = 0; //NP modified C.K. inits properties in constructor, do not overwrite

  // perform initial allocation of atom-based arrays
  // register with Atom class

  extended = orientflag = dorientflag = 0;
  body = NULL;
  displace = NULL;
  eflags = NULL;
  orient = NULL;
  dorient = NULL;
  grow_arrays(atom->nmax);
  atom->add_callback(0);

  if (strcmp(this->style,"rigid")) return;  //NP modified C.K.

  // parse args for rigid body specification
  // set nbody and body[i] for each atom

  if (narg < 4) error->all(FLERR,"Illegal fix rigid command");
  int iarg;

  mol2body = NULL;
  body2mol = NULL;

  // single rigid body
  // nbody = 1
  // all atoms in fix group are part of body

  if (strcmp(arg[3],"single") == 0) {
    rstyle = SINGLE;
    iarg = 4;
    nbody = 1;

    int *mask = atom->mask;
    int nlocal = atom->nlocal;

    for (i = 0; i < nlocal; i++) {
      body[i] = -1;
      if (mask[i] & groupbit) body[i] = 0;
    }

  // each molecule in fix group is a rigid body
  // maxmol = largest molecule #
  // ncount = # of atoms in each molecule (have to sum across procs)
  // nbody = # of non-zero ncount values
  // use nall as incremented ptr to set body[] values for each atom

  } else if (strcmp(arg[3],"molecule") == 0) {
    rstyle = MOLECULE;
    iarg = 4;
    if (atom->molecule_flag == 0)
      error->all(FLERR,"Fix rigid molecule requires atom attribute molecule");

    int *mask = atom->mask;
    int *molecule = atom->molecule;
    int nlocal = atom->nlocal;

    maxmol = -1;
    for (i = 0; i < nlocal; i++)
      if (mask[i] & groupbit) maxmol = MAX(maxmol,molecule[i]);

    int itmp;
    MPI_Allreduce(&maxmol,&itmp,1,MPI_INT,MPI_MAX,world);
    maxmol = itmp;

    int *ncount;
    memory->create(ncount,maxmol+1,"rigid:ncount");
    for (i = 0; i <= maxmol; i++) ncount[i] = 0;

    for (i = 0; i < nlocal; i++)
      if (mask[i] & groupbit) ncount[molecule[i]]++;

    memory->create(mol2body,maxmol+1,"rigid:mol2body");
    MPI_Allreduce(ncount,mol2body,maxmol+1,MPI_INT,MPI_SUM,world);

    nbody = 0;
    for (i = 0; i <= maxmol; i++)
      if (mol2body[i]) mol2body[i] = nbody++;
      else mol2body[i] = -1;

    memory->create(body2mol,nbody,"rigid:body2mol");

    nbody = 0;
    for (i = 0; i <= maxmol; i++)
      if (mol2body[i] >= 0) body2mol[nbody++] = i;

    for (i = 0; i < nlocal; i++) {
      body[i] = -1;
      if (mask[i] & groupbit) body[i] = mol2body[molecule[i]];
    }

    memory->destroy(ncount);

  // each listed group is a rigid body
  // check if all listed groups exist
  // an atom must belong to fix group and listed group to be in rigid body
  // error if atom belongs to more than 1 rigid body

  } else if (strcmp(arg[3],"group") == 0) {
    if (narg < 5) error->all(FLERR,"Illegal fix rigid command");
    rstyle = GROUP;
    nbody = force->inumeric(FLERR,arg[4]);
    if (nbody <= 0) error->all(FLERR,"Illegal fix rigid command");
    if (narg < 5+nbody) error->all(FLERR,"Illegal fix rigid command");
    iarg = 5+nbody;

    int *igroups = new int[nbody];
    for (ibody = 0; ibody < nbody; ibody++) {
      igroups[ibody] = group->find(arg[5+ibody]);
      if (igroups[ibody] == -1)
        error->all(FLERR,"Could not find fix rigid group ID");
    }

    int *mask = atom->mask;
    int nlocal = atom->nlocal;

    int flag = 0;
    for (i = 0; i < nlocal; i++) {
      body[i] = -1;
      if (mask[i] & groupbit)
        for (ibody = 0; ibody < nbody; ibody++)
          if (mask[i] & group->bitmask[igroups[ibody]]) {
            if (body[i] >= 0) flag = 1;
            body[i] = ibody;
          }
    }

    int flagall;
    MPI_Allreduce(&flag,&flagall,1,MPI_INT,MPI_SUM,world);
    if (flagall)
      error->all(FLERR,"One or more atoms belong to multiple rigid bodies");

    delete [] igroups;

  } else error->all(FLERR,"Illegal fix rigid command");

  // error check on nbody

  if (nbody == 0) error->all(FLERR,"No rigid bodies defined");

  // create all nbody-length arrays

  memory->create(nrigid,nbody,"rigid:nrigid");
  memory->create(masstotal,nbody,"rigid:masstotal");
  memory->create(xcm,nbody,3,"rigid:xcm");
  memory->create(vcm,nbody,3,"rigid:vcm");
  memory->create(fcm,nbody,3,"rigid:fcm");
  memory->create(inertia,nbody,3,"rigid:inertia");
  memory->create(ex_space,nbody,3,"rigid:ex_space");
  memory->create(ey_space,nbody,3,"rigid:ey_space");
  memory->create(ez_space,nbody,3,"rigid:ez_space");
  memory->create(angmom,nbody,3,"rigid:angmom");
  memory->create(omega,nbody,3,"rigid:omega");
  memory->create(torque,nbody,3,"rigid:torque");
  memory->create(quat,nbody,4,"rigid:quat");
  memory->create(imagebody,nbody,"rigid:imagebody");
  memory->create(fflag,nbody,3,"rigid:fflag");
  memory->create(tflag,nbody,3,"rigid:tflag");
  memory->create(langextra,nbody,6,"rigid:langextra");

  memory->create(sum,nbody,6,"rigid:sum");
  memory->create(all,nbody,6,"rigid:all");
  memory->create(remapflag,nbody,4,"rigid:remapflag");

  // initialize force/torque flags to default = 1.0
  // for 2d: fz, tx, ty = 0.0

  array_flag = 1;
  size_array_rows = nbody;
  size_array_cols = 15;
  global_freq = 1;
  extarray = 0;

  for (i = 0; i < nbody; i++) {
    fflag[i][0] = fflag[i][1] = fflag[i][2] = 1.0;
    tflag[i][0] = tflag[i][1] = tflag[i][2] = 1.0;
    if (domain->dimension == 2) fflag[i][2] = tflag[i][0] = tflag[i][1] = 0.0;
  }

  // parse optional args

  int seed;
  langflag = 0;
  tstat_flag = 0;
  pstat_flag = 0;
  allremap = 1;
  id_dilate = NULL;
  t_chain = 10;
  t_iter = 1;
  t_order = 3;
  p_chain = 10;
  infile = NULL;

  pcouple = NONE;
  pstyle = ANISO;
  dimension = domain->dimension;

  for (int i = 0; i < 3; i++) {
    p_start[i] = p_stop[i] = p_period[i] = 0.0;
    p_flag[i] = 0;
  }

  while (iarg < narg) {
    if (strcmp(arg[iarg],"force") == 0) {
      if (iarg+5 > narg) error->all(FLERR,"Illegal fix rigid command");

      int mlo,mhi;
      force->bounds(arg[iarg+1],nbody,mlo,mhi);

      double xflag,yflag,zflag;
      if (strcmp(arg[iarg+2],"off") == 0) xflag = 0.0;
      else if (strcmp(arg[iarg+2],"on") == 0) xflag = 1.0;
      else error->all(FLERR,"Illegal fix rigid command");
      if (strcmp(arg[iarg+3],"off") == 0) yflag = 0.0;
      else if (strcmp(arg[iarg+3],"on") == 0) yflag = 1.0;
      else error->all(FLERR,"Illegal fix rigid command");
      if (strcmp(arg[iarg+4],"off") == 0) zflag = 0.0;
      else if (strcmp(arg[iarg+4],"on") == 0) zflag = 1.0;
      else error->all(FLERR,"Illegal fix rigid command");

      if (domain->dimension == 2 && zflag == 1.0)
        error->all(FLERR,"Fix rigid z force cannot be on for 2d simulation");

      int count = 0;
      for (int m = mlo; m <= mhi; m++) {
        fflag[m-1][0] = xflag;
        fflag[m-1][1] = yflag;
        fflag[m-1][2] = zflag;
        count++;
      }
      if (count == 0) error->all(FLERR,"Illegal fix rigid command");

      iarg += 5;

    } else if (strcmp(arg[iarg],"torque") == 0) {
      if (iarg+5 > narg) error->all(FLERR,"Illegal fix rigid command");

      int mlo,mhi;
      force->bounds(arg[iarg+1],nbody,mlo,mhi);

      double xflag,yflag,zflag;
      if (strcmp(arg[iarg+2],"off") == 0) xflag = 0.0;
      else if (strcmp(arg[iarg+2],"on") == 0) xflag = 1.0;
      else error->all(FLERR,"Illegal fix rigid command");
      if (strcmp(arg[iarg+3],"off") == 0) yflag = 0.0;
      else if (strcmp(arg[iarg+3],"on") == 0) yflag = 1.0;
      else error->all(FLERR,"Illegal fix rigid command");
      if (strcmp(arg[iarg+4],"off") == 0) zflag = 0.0;
      else if (strcmp(arg[iarg+4],"on") == 0) zflag = 1.0;
      else error->all(FLERR,"Illegal fix rigid command");

      if (domain->dimension == 2 && (xflag == 1.0 || yflag == 1.0))
        error->all(FLERR,"Fix rigid xy torque cannot be on for 2d simulation");

      int count = 0;
      for (int m = mlo; m <= mhi; m++) {
        tflag[m-1][0] = xflag;
        tflag[m-1][1] = yflag;
        tflag[m-1][2] = zflag;
        count++;
      }
      if (count == 0) error->all(FLERR,"Illegal fix rigid command");

      iarg += 5;

    } else if (strcmp(arg[iarg],"langevin") == 0) {
      if (iarg+5 > narg) error->all(FLERR,"Illegal fix rigid command");
      if (strcmp(style,"rigid") != 0 && strcmp(style,"rigid/nve") != 0)
        error->all(FLERR,"Illegal fix rigid command");
      langflag = 1;
      t_start = force->numeric(FLERR,arg[iarg+1]);
      t_stop = force->numeric(FLERR,arg[iarg+2]);
      t_period = force->numeric(FLERR,arg[iarg+3]);
      seed = force->inumeric(FLERR,arg[iarg+4]);
      if (t_period <= 0.0)
        error->all(FLERR,"Fix rigid langevin period must be > 0.0");
      if (seed <= 0) error->all(FLERR,"Illegal fix rigid command");
      iarg += 5;

    } else if (strcmp(arg[iarg],"temp") == 0) {
      if (iarg+4 > narg) error->all(FLERR,"Illegal fix rigid command");
      if (strcmp(style,"rigid/nvt") != 0 && strcmp(style,"rigid/npt") != 0)
        error->all(FLERR,"Illegal fix rigid command");
      tstat_flag = 1;
      t_start = force->numeric(FLERR,arg[iarg+1]);
      t_stop = force->numeric(FLERR,arg[iarg+2]);
      t_period = force->numeric(FLERR,arg[iarg+3]);
      iarg += 4;

    } else if (strcmp(arg[iarg],"iso") == 0) {
      if (iarg+4 > narg) error->all(FLERR,"Illegal fix rigid command");
      if (strcmp(style,"rigid/npt") != 0 && strcmp(style,"rigid/nph") != 0)
        error->all(FLERR,"Illegal fix rigid command");
      pcouple = XYZ;
      p_start[0] = p_start[1] = p_start[2] = force->numeric(FLERR,arg[iarg+1]);
      p_stop[0] = p_stop[1] = p_stop[2] = force->numeric(FLERR,arg[iarg+2]);
      p_period[0] = p_period[1] = p_period[2] =
        force->numeric(FLERR,arg[iarg+3]);
      p_flag[0] = p_flag[1] = p_flag[2] = 1;
      if (dimension == 2) {
	      p_start[2] = p_stop[2] = p_period[2] = 0.0;
      	p_flag[2] = 0;
      }
      iarg += 4;
    } else if (strcmp(arg[iarg],"aniso") == 0) {
      if (iarg+4 > narg) error->all(FLERR,"Illegal fix rigid command");
      if (strcmp(style,"rigid/npt") != 0 && strcmp(style,"rigid/nph") != 0)
	      error->all(FLERR,"Illegal fix rigid command");
      p_start[0] = p_start[1] = p_start[2] = force->numeric(FLERR,arg[iarg+1]);
      p_stop[0] = p_stop[1] = p_stop[2] = force->numeric(FLERR,arg[iarg+2]);
      p_period[0] = p_period[1] = p_period[2] =
        force->numeric(FLERR,arg[iarg+3]);
      p_flag[0] = p_flag[1] = p_flag[2] = 1;
      if (dimension == 2) {
      	p_start[2] = p_stop[2] = p_period[2] = 0.0;
	      p_flag[2] = 0;
      }
      iarg += 4;

    } else if (strcmp(arg[iarg],"x") == 0) {
      if (iarg+4 > narg) error->all(FLERR,"Illegal fix rigid command");
      p_start[0] = force->numeric(FLERR,arg[iarg+1]);
      p_stop[0] = force->numeric(FLERR,arg[iarg+2]);
      p_period[0] = force->numeric(FLERR,arg[iarg+3]);
      p_flag[0] = 1;
      iarg += 4;

    } else if (strcmp(arg[iarg],"y") == 0) {
      if (iarg+4 > narg) error->all(FLERR,"Illegal fix rigid command");
      p_start[1] = force->numeric(FLERR,arg[iarg+1]);
      p_stop[1] = force->numeric(FLERR,arg[iarg+2]);
      p_period[1] = force->numeric(FLERR,arg[iarg+3]);
      p_flag[1] = 1;
      iarg += 4;

    } else if (strcmp(arg[iarg],"z") == 0) {
      if (iarg+4 > narg) error->all(FLERR,"Illegal fix rigid command");
      p_start[2] = force->numeric(FLERR,arg[iarg+1]);
      p_stop[2] = force->numeric(FLERR,arg[iarg+2]);
      p_period[2] = force->numeric(FLERR,arg[iarg+3]);
      p_flag[2] = 1;
      iarg += 4;

    } else if (strcmp(arg[iarg],"couple") == 0) {
      if (iarg+2 > narg) error->all(FLERR,"Illegal fix rigid command");
      if (strcmp(arg[iarg+1],"xyz") == 0) pcouple = XYZ;
      else if (strcmp(arg[iarg+1],"xy") == 0) pcouple = XY;
      else if (strcmp(arg[iarg+1],"yz") == 0) pcouple = YZ;
      else if (strcmp(arg[iarg+1],"xz") == 0) pcouple = XZ;
      else if (strcmp(arg[iarg+1],"none") == 0) pcouple = NONE;
      else error->all(FLERR,"Illegal fix rigid command");
      iarg += 2;

    } else if (strcmp(arg[iarg],"dilate") == 0) {
      if (iarg+2 > narg)
        error->all(FLERR,"Illegal fix rigid nvt/npt/nph command");
      if (strcmp(arg[iarg+1],"all") == 0) allremap = 1;
      else {
        allremap = 0;
        delete [] id_dilate;
        int n = strlen(arg[iarg+1]) + 1;
        id_dilate = new char[n];
        strcpy(id_dilate,arg[iarg+1]);
        int idilate = group->find(id_dilate);
        if (idilate == -1)
          error->all(FLERR,
                     "Fix rigid npt/nph dilate group ID does not exist");
      }
      iarg += 2;

    } else if (strcmp(arg[iarg],"tparam") == 0) {
      if (iarg+4 > narg) error->all(FLERR,"Illegal fix rigid command");
      if (strcmp(style,"rigid/nvt") != 0 && strcmp(style,"rigid/npt") != 0)
        error->all(FLERR,"Illegal fix rigid command");
      t_chain = force->inumeric(FLERR,arg[iarg+1]);
      t_iter = force->inumeric(FLERR,arg[iarg+2]);
      t_order = force->inumeric(FLERR,arg[iarg+3]);
      iarg += 4;

    } else if (strcmp(arg[iarg],"pchain") == 0) {
      if (iarg+2 > narg) error->all(FLERR,"Illegal fix rigid command");
      if (strcmp(style,"rigid/npt") != 0 && strcmp(style,"rigid/nph") != 0)
        error->all(FLERR,"Illegal fix rigid command");
      p_chain = force->inumeric(FLERR,arg[iarg+1]);
      iarg += 2;

    } else if (strcmp(arg[iarg],"infile") == 0) {
      if (iarg+2 > narg) error->all(FLERR,"Illegal fix rigid command");
      delete [] infile;
      int n = strlen(arg[iarg+1]) + 1;
      infile = new char[n];
      strcpy(infile,arg[iarg+1]);
      restart_file = 1;
      iarg += 2;

    } else error->all(FLERR,"Illegal fix rigid command");
  }
  // set pstat_flag

  pstat_flag = 0;
  for (int i = 0; i < 3; i++)
    if (p_flag[i]) pstat_flag = 1;

  if (pcouple == XYZ || (dimension == 2 && pcouple == XY)) pstyle = ISO;
  else pstyle = ANISO;

  // initialize Marsaglia RNG with processor-unique seed

  if (langflag) random = new RanMars(lmp,seed + me);
  else random = NULL;

  // initialize vector output quantities in case accessed before run

  for (i = 0; i < nbody; i++) {
    xcm[i][0] = xcm[i][1] = xcm[i][2] = 0.0;
    vcm[i][0] = vcm[i][1] = vcm[i][2] = 0.0;
    fcm[i][0] = fcm[i][1] = fcm[i][2] = 0.0;
    torque[i][0] = torque[i][1] = torque[i][2] = 0.0;
  }

  // nrigid[n] = # of atoms in Nth rigid body
  // error if one or zero atoms

  int *ncount = new int[nbody];
  for (ibody = 0; ibody < nbody; ibody++) ncount[ibody] = 0;

  int nlocal = atom->nlocal;

  for (i = 0; i < nlocal; i++)
    if (body[i] >= 0) ncount[body[i]]++;

  MPI_Allreduce(ncount,nrigid,nbody,MPI_INT,MPI_SUM,world);
  delete [] ncount;

  for (ibody = 0; ibody < nbody; ibody++)
    if (nrigid[ibody] <= 1) error->all(FLERR,"One or zero atoms in rigid body");

  // bitmasks for properties of extended particles

  POINT = 1;
  SPHERE = 2;
  ELLIPSOID = 4;
  LINE = 8;
  TRIANGLE = 16;
  DIPOLE = 32;
  OMEGA = 64;
  ANGMOM = 128;
  TORQUE = 256;

  MINUSPI = -MY_PI;
  TWOPI = 2.0*MY_PI;

  // print statistics

  int nsum = 0;
  for (ibody = 0; ibody < nbody; ibody++) nsum += nrigid[ibody];

  if (me == 0) {
    if (screen) fprintf(screen,"%d rigid bodies with %d atoms\n",nbody,nsum);
    if (logfile) fprintf(logfile,"%d rigid bodies with %d atoms\n",nbody,nsum);
  }
  // firstflag = 1 triggers one-time initialization of rigid body attributes

  firstflag = 1;
}

/* ---------------------------------------------------------------------- */

FixRigid::~FixRigid()
{
  // unregister callbacks to this fix from Atom class

  atom->delete_callback(id,0);

  delete random;

  delete [] infile;
  memory->destroy(mol2body);
  memory->destroy(body2mol);

  // delete locally stored arrays

  memory->destroy(body);
  memory->destroy(displace);
  memory->destroy(eflags);
  memory->destroy(orient);
  memory->destroy(dorient);

  // delete nbody-length arrays

  memory->destroy(nrigid);
  memory->destroy(masstotal);
  memory->destroy(xcm);
  memory->destroy(vcm);
  memory->destroy(fcm);
  memory->destroy(inertia);
  memory->destroy(ex_space);
  memory->destroy(ey_space);
  memory->destroy(ez_space);
  memory->destroy(angmom);
  memory->destroy(omega);
  memory->destroy(torque);
  memory->destroy(quat);
  memory->destroy(imagebody);
  memory->destroy(fflag);
  memory->destroy(tflag);
  memory->destroy(langextra);

  memory->destroy(sum);
  memory->destroy(all);
  memory->destroy(remapflag);
}

/* ---------------------------------------------------------------------- */

int FixRigid::setmask()
{
  int mask = 0;
  mask |= INITIAL_INTEGRATE;
  mask |= FINAL_INTEGRATE;
  if (langflag) mask |= POST_FORCE;
  mask |= PRE_NEIGHBOR;
  mask |= INITIAL_INTEGRATE_RESPA;
  mask |= FINAL_INTEGRATE_RESPA;
  return mask;
}

/* ---------------------------------------------------------------------- */

void FixRigid::init()
{
  int i,ibody;

  triclinic = domain->triclinic;
  // atom style pointers to particles that store extra info

  avec_ellipsoid = (AtomVecEllipsoid *) atom->style_match("ellipsoid");
  avec_line = (AtomVecLine *) atom->style_match("line");
  avec_tri = (AtomVecTri *) atom->style_match("tri");

  // warn if more than one rigid fix

  int count = 0;
  for (i = 0; i < modify->nfix; i++)
    if (strcmp(modify->fix[i]->style,"rigid") == 0) count++;
  if (count > 1 && me == 0) error->warning(FLERR,"More than one fix rigid");

  // error if npt,nph fix comes before rigid fix

  for (i = 0; i < modify->nfix; i++) {
    if (strcmp(modify->fix[i]->style,"npt") == 0) break;
    if (strcmp(modify->fix[i]->style,"nph") == 0) break;
  }
  if (i < modify->nfix) {
    for (int j = i; j < modify->nfix; j++)
      if (strcmp(modify->fix[j]->style,"rigid") == 0)
        error->all(FLERR,"Rigid fix must come before NPT/NPH fix");
  }

  // timestep info

  dtv = update->dt;
  dtf = 0.5 * update->dt * force->ftm2v;
  dtq = 0.5 * update->dt;

  if (strstr(update->integrate_style,"respa"))
    step_respa = ((Respa *) update->integrate)->step;

  // one-time initialization of rigid body attributes
  // setup_bodies_static = extended flags, masstotal, COM, inertia tensor
  // setup_bodies_dynamic = vcm and angmom

  if (firstflag) {
    firstflag = 0;
    setup_bodies_static();
    setup_bodies_dynamic();
  }

  // temperature scale factor

  double ndof = 0.0;
  for (ibody = 0; ibody < nbody; ibody++) {
    ndof += fflag[ibody][0] + fflag[ibody][1] + fflag[ibody][2];
    ndof += tflag[ibody][0] + tflag[ibody][1] + tflag[ibody][2];
  }
  if (ndof > 0.0) tfactor = force->mvv2e / (ndof * force->boltz);
  else tfactor = 0.0;
}

/* ----------------------------------------------------------------------
   compute initial fcm and torque on bodies, also initial virial
   reset all particle velocities to be consistent with vcm and omega
------------------------------------------------------------------------- */

void FixRigid::setup(int vflag)
{
  int i,n,ibody;
  double massone,radone;

  // fcm = force on center-of-mass of each rigid body

  double **f = atom->f;
  int *type = atom->type;
  int nlocal = atom->nlocal;

  for (ibody = 0; ibody < nbody; ibody++)
    for (i = 0; i < 6; i++) sum[ibody][i] = 0.0;

  for (i = 0; i < nlocal; i++) {
    if (body[i] < 0) continue;
    ibody = body[i];
    sum[ibody][0] += f[i][0];
    sum[ibody][1] += f[i][1];
    sum[ibody][2] += f[i][2];
  }

  MPI_Allreduce(sum[0],all[0],6*nbody,MPI_DOUBLE,MPI_SUM,world);

  for (ibody = 0; ibody < nbody; ibody++) {
    fcm[ibody][0] = all[ibody][0];
    fcm[ibody][1] = all[ibody][1];
    fcm[ibody][2] = all[ibody][2];
  }

  // torque = torque on each rigid body

  tagint *image = atom->image;
  double **x = atom->x;

  double dx,dy,dz;
  double unwrap[3];

  for (ibody = 0; ibody < nbody; ibody++)
    for (i = 0; i < 6; i++) sum[ibody][i] = 0.0;

  for (i = 0; i < nlocal; i++) {
    if (body[i] < 0) continue;
    ibody = body[i];

    domain->unmap(x[i],image[i],unwrap);
    dx = unwrap[0] - xcm[ibody][0];
    dy = unwrap[1] - xcm[ibody][1];
    dz = unwrap[2] - xcm[ibody][2];

    sum[ibody][0] += dy * f[i][2] - dz * f[i][1];
    sum[ibody][1] += dz * f[i][0] - dx * f[i][2];
    sum[ibody][2] += dx * f[i][1] - dy * f[i][0];
    }

  // extended particles add their torque to torque of body

  if (extended) {
    double **torque_one = atom->torque;

    for (i = 0; i < nlocal; i++) {
      if (body[i] < 0) continue;
      ibody = body[i];

      if (eflags[i] & TORQUE) {
        sum[ibody][0] += torque_one[i][0];
        sum[ibody][1] += torque_one[i][1];
        sum[ibody][2] += torque_one[i][2];
      }
    }
  }

  MPI_Allreduce(sum[0],all[0],6*nbody,MPI_DOUBLE,MPI_SUM,world);

  for (ibody = 0; ibody < nbody; ibody++) {
    torque[ibody][0] = all[ibody][0];
    torque[ibody][1] = all[ibody][1];
    torque[ibody][2] = all[ibody][2];
  }

  // zero langextra in case Langevin thermostat not used
  // no point to calling post_force() here since langextra
  //   is only added to fcm/torque in final_integrate()

  for (ibody = 0; ibody < nbody; ibody++)
    for (i = 0; i < 6; i++) langextra[ibody][i] = 0.0;

  // virial setup before call to set_v

  if (vflag) v_setup(vflag);
  else evflag = 0;

  // set velocities from angmom & omega

  for (ibody = 0; ibody < nbody; ibody++)
    MathExtra::angmom_to_omega(angmom[ibody],ex_space[ibody],ey_space[ibody],
                               ez_space[ibody],inertia[ibody],omega[ibody]);
  set_v();

  // guesstimate virial as 2x the set_v contribution

  if (vflag_global)
    for (n = 0; n < 6; n++) virial[n] *= 2.0;
  if (vflag_atom) {
    for (i = 0; i < nlocal; i++)
      for (n = 0; n < 6; n++)
        vatom[i][n] *= 2.0;
  }
}

/* ---------------------------------------------------------------------- */

void FixRigid::initial_integrate(int vflag)
{
  double dtfm;

  for (int ibody = 0; ibody < nbody; ibody++) {

    // update vcm by 1/2 step

    dtfm = dtf / masstotal[ibody];
    vcm[ibody][0] += dtfm * fcm[ibody][0] * fflag[ibody][0];
    vcm[ibody][1] += dtfm * fcm[ibody][1] * fflag[ibody][1];
    vcm[ibody][2] += dtfm * fcm[ibody][2] * fflag[ibody][2];

    // update xcm by full step

    xcm[ibody][0] += dtv * vcm[ibody][0];
    xcm[ibody][1] += dtv * vcm[ibody][1];
    xcm[ibody][2] += dtv * vcm[ibody][2];

    // update angular momentum by 1/2 step

    angmom[ibody][0] += dtf * torque[ibody][0] * tflag[ibody][0];
    angmom[ibody][1] += dtf * torque[ibody][1] * tflag[ibody][1];
    angmom[ibody][2] += dtf * torque[ibody][2] * tflag[ibody][2];

    // compute omega at 1/2 step from angmom at 1/2 step and current q
    // update quaternion a full step via Richardson iteration
    // returns new normalized quaternion, also updated omega at 1/2 step
    // update ex,ey,ez to reflect new quaternion

    MathExtra::angmom_to_omega(angmom[ibody],ex_space[ibody],ey_space[ibody],
                               ez_space[ibody],inertia[ibody],omega[ibody]);
    MathExtra::richardson(quat[ibody],angmom[ibody],omega[ibody],
                          inertia[ibody],dtq);
    MathExtra::q_to_exyz(quat[ibody],
                         ex_space[ibody],ey_space[ibody],ez_space[ibody]);
  }

  // virial setup before call to set_xv

  if (vflag) v_setup(vflag);
  else evflag = 0;

  // set coords/orient and velocity/rotation of atoms in rigid bodies
  // from quarternion and omega

  set_xv();
}

/* ----------------------------------------------------------------------
   apply Langevin thermostat to all 6 DOF of rigid bodies
   computed by proc 0, broadcast to other procs
   unlike fix langevin, this stores extra force in extra arrays,
     which are added in when final_integrate() calculates a new fcm/torque
------------------------------------------------------------------------- */

void FixRigid::post_force(int vflag)
{
  if (me == 0) {
    double gamma1,gamma2;

    double delta = update->ntimestep - update->beginstep;
    if (delta != 0.0) delta /= update->endstep - update->beginstep;
    t_target = t_start + delta * (t_stop-t_start);
    double tsqrt = sqrt(t_target);

    double boltz = force->boltz;
    double dt = update->dt;
    double mvv2e = force->mvv2e;
    double ftm2v = force->ftm2v;

    for (int i = 0; i < nbody; i++) {
      gamma1 = -masstotal[i] / t_period / ftm2v;
      gamma2 = sqrt(masstotal[i]) * tsqrt *
        sqrt(24.0*boltz/t_period/dt/mvv2e) / ftm2v;
      langextra[i][0] = gamma1*vcm[i][0] + gamma2*(random->uniform()-0.5);
      langextra[i][1] = gamma1*vcm[i][1] + gamma2*(random->uniform()-0.5);
      langextra[i][2] = gamma1*vcm[i][2] + gamma2*(random->uniform()-0.5);

      gamma1 = -1.0 / t_period / ftm2v;
      gamma2 = tsqrt * sqrt(24.0*boltz/t_period/dt/mvv2e) / ftm2v;
      langextra[i][3] = inertia[i][0]*gamma1*omega[i][0] +
        sqrt(inertia[i][0])*gamma2*(random->uniform()-0.5);
      langextra[i][4] = inertia[i][1]*gamma1*omega[i][1] +
        sqrt(inertia[i][1])*gamma2*(random->uniform()-0.5);
      langextra[i][5] = inertia[i][2]*gamma1*omega[i][2] +
        sqrt(inertia[i][2])*gamma2*(random->uniform()-0.5);
    }
  }

  MPI_Bcast(&langextra[0][0],6*nbody,MPI_DOUBLE,0,world);
}

/* ---------------------------------------------------------------------- */

void FixRigid::final_integrate()
{
  int i,ibody;
  double dtfm;

  // sum over atoms to get force and torque on rigid body

  tagint *image = atom->image;
  double **x = atom->x;
  double **f = atom->f;
  int nlocal = atom->nlocal;

  double dx,dy,dz;
  double unwrap[3];

  for (ibody = 0; ibody < nbody; ibody++)
    for (i = 0; i < 6; i++) sum[ibody][i] = 0.0;

  for (i = 0; i < nlocal; i++) {
    if (body[i] < 0) continue;
    ibody = body[i];

    sum[ibody][0] += f[i][0];
    sum[ibody][1] += f[i][1];
    sum[ibody][2] += f[i][2];

    domain->unmap(x[i],image[i],unwrap);
    dx = unwrap[0] - xcm[ibody][0];
    dy = unwrap[1] - xcm[ibody][1];
    dz = unwrap[2] - xcm[ibody][2];

    sum[ibody][3] += dy*f[i][2] - dz*f[i][1];
    sum[ibody][4] += dz*f[i][0] - dx*f[i][2];
    sum[ibody][5] += dx*f[i][1] - dy*f[i][0];
  }

  // extended particles add their torque to torque of body

  if (extended) {
    double **torque_one = atom->torque;

    for (i = 0; i < nlocal; i++) {
      if (body[i] < 0) continue;
      ibody = body[i];

      if (eflags[i] & TORQUE) {
        sum[ibody][3] += torque_one[i][0];
        sum[ibody][4] += torque_one[i][1];
        sum[ibody][5] += torque_one[i][2];
      }
    }
  }

  MPI_Allreduce(sum[0],all[0],6*nbody,MPI_DOUBLE,MPI_SUM,world);

  // update vcm and angmom
  // include Langevin thermostat forces
  // fflag,tflag = 0 for some dimensions in 2d

  for (ibody = 0; ibody < nbody; ibody++) {
    fcm[ibody][0] = all[ibody][0] + langextra[ibody][0];
    fcm[ibody][1] = all[ibody][1] + langextra[ibody][1];
    fcm[ibody][2] = all[ibody][2] + langextra[ibody][2];
    torque[ibody][0] = all[ibody][3] + langextra[ibody][3];
    torque[ibody][1] = all[ibody][4] + langextra[ibody][4];
    torque[ibody][2] = all[ibody][5] + langextra[ibody][5];

    // update vcm by 1/2 step

    dtfm = dtf / masstotal[ibody];
    vcm[ibody][0] += dtfm * fcm[ibody][0] * fflag[ibody][0];
    vcm[ibody][1] += dtfm * fcm[ibody][1] * fflag[ibody][1];
    vcm[ibody][2] += dtfm * fcm[ibody][2] * fflag[ibody][2];

    // update angular momentum by 1/2 step

    angmom[ibody][0] += dtf * torque[ibody][0] * tflag[ibody][0];
    angmom[ibody][1] += dtf * torque[ibody][1] * tflag[ibody][1];
    angmom[ibody][2] += dtf * torque[ibody][2] * tflag[ibody][2];

    MathExtra::angmom_to_omega(angmom[ibody],ex_space[ibody],ey_space[ibody],
                               ez_space[ibody],inertia[ibody],omega[ibody]);
  }

  // set velocity/rotation of atoms in rigid bodies
  // virial is already setup from initial_integrate

  set_v();
}

/* ----------------------------------------------------------------------
   apply evolution operators to quat, quat momentum
   see Miller paper cited in fix rigid/nvt and fix rigid/npt
------------------------------------------------------------------------- */

void FixRigid::no_squish_rotate(int k, double *p, double *q,
                                double *inertia, double dt) const
{
  double phi,c_phi,s_phi,kp[4],kq[4];

  // apply permuation operator on p and q, get kp and kq

  if (k == 1) {
    kq[0] = -q[1];  kp[0] = -p[1];
    kq[1] =  q[0];  kp[1] =  p[0];
    kq[2] =  q[3];  kp[2] =  p[3];
    kq[3] = -q[2];  kp[3] = -p[2];
  } else if (k == 2) {
    kq[0] = -q[2];  kp[0] = -p[2];
    kq[1] = -q[3];  kp[1] = -p[3];
    kq[2] =  q[0];  kp[2] =  p[0];
    kq[3] =  q[1];  kp[3] =  p[1];
  } else if (k == 3) {
    kq[0] = -q[3];  kp[0] = -p[3];
    kq[1] =  q[2];  kp[1] =  p[2];
    kq[2] = -q[1];  kp[2] = -p[1];
    kq[3] =  q[0];  kp[3] =  p[0];
  }

  // obtain phi, cosines and sines

  phi = p[0]*kq[0] + p[1]*kq[1] + p[2]*kq[2] + p[3]*kq[3];
  if (fabs(inertia[k-1]) < 1e-6) phi *= 0.0;
  else phi /= 4.0 * inertia[k-1];
  c_phi = cos(dt * phi);
  s_phi = sin(dt * phi);

  // advance p and q

  p[0] = c_phi*p[0] + s_phi*kp[0];
  p[1] = c_phi*p[1] + s_phi*kp[1];
  p[2] = c_phi*p[2] + s_phi*kp[2];
  p[3] = c_phi*p[3] + s_phi*kp[3];

  q[0] = c_phi*q[0] + s_phi*kq[0];
  q[1] = c_phi*q[1] + s_phi*kq[1];
  q[2] = c_phi*q[2] + s_phi*kq[2];
  q[3] = c_phi*q[3] + s_phi*kq[3];
}

/* ---------------------------------------------------------------------- */

void FixRigid::initial_integrate_respa(int vflag, int ilevel, int iloop)
{
  dtv = step_respa[ilevel];
  dtf = 0.5 * step_respa[ilevel] * force->ftm2v;
  dtq = 0.5 * step_respa[ilevel];

  if (ilevel == 0) initial_integrate(vflag);
  else final_integrate();
}

/* ---------------------------------------------------------------------- */

void FixRigid::final_integrate_respa(int ilevel, int iloop)
{
  dtf = 0.5 * step_respa[ilevel] * force->ftm2v;
  final_integrate();
}

/* ----------------------------------------------------------------------
   remap xcm of each rigid body back into periodic simulation box
   done during pre_neighbor so will be after call to pbc()
     and after fix_deform::pre_exchange() may have flipped box
   use domain->remap() in case xcm is far away from box
     due to 1st definition of rigid body or due to box flip
   if don't do this, then atoms of a body which drifts far away
     from a triclinic box will be remapped back into box
     with huge displacements when the box tilt changes via set_x()
   adjust image flag of body and image flags of all atoms in body
------------------------------------------------------------------------- */

void FixRigid::pre_neighbor()
{
  tagint original,oldimage,newimage;

  for (int ibody = 0; ibody < nbody; ibody++) {
    original = imagebody[ibody];
    domain->remap(xcm[ibody],imagebody[ibody]);

    if (original == imagebody[ibody]) remapflag[ibody][3] = 0;
    else {
      oldimage = original & IMGMASK;
      newimage = imagebody[ibody] & IMGMASK;
      remapflag[ibody][0] = newimage - oldimage;
      oldimage = (original >> IMGBITS) & IMGMASK;
      newimage = (imagebody[ibody] >> IMGBITS) & IMGMASK;
      remapflag[ibody][1] = newimage - oldimage;
      oldimage = original >> IMG2BITS;
      newimage = imagebody[ibody] >> IMG2BITS;
      remapflag[ibody][2] = newimage - oldimage;
      remapflag[ibody][3] = 1;
    }
  }

  // adjust image flags of any atom in a rigid body whose xcm was remapped
  // subtracting remapflag = new-old keeps ix,iy,iz near 0
  //   so body is always in central simulation box

  tagint *image = atom->image;
  int nlocal = atom->nlocal;

  int ibody;
  tagint idim,otherdims;

  for (int i = 0; i < nlocal; i++) {
    if (body[i] == -1) continue;
    if (remapflag[body[i]][3] == 0) continue;
    ibody = body[i];

    if (remapflag[ibody][0]) {
      idim = image[i] & IMGMASK;
      otherdims = image[i] ^ idim;
      idim -= remapflag[ibody][0];
      idim &= IMGMASK;
      image[i] = otherdims | idim;
    }
    if (remapflag[ibody][1]) {
      idim = (image[i] >> IMGBITS) & IMGMASK;
      otherdims = image[i] ^ (idim << IMGBITS);
      idim -= remapflag[ibody][1];
      idim &= IMGMASK;
      image[i] = otherdims | (idim << IMGBITS);
    }
    if (remapflag[ibody][2]) {
      idim = image[i] >> IMG2BITS;
      otherdims = image[i] ^ (idim << IMG2BITS);
      idim -= remapflag[ibody][2];
      idim &= IMGMASK;
      image[i] = otherdims | (idim << IMG2BITS);
    }
  }
}

/* ----------------------------------------------------------------------
   count # of DOF removed by rigid bodies for atoms in igroup
   return total count of DOF
------------------------------------------------------------------------- */

int FixRigid::dof(int tgroup)
{
  // cannot count DOF correctly unless setup_bodies_static() has been called

  if (firstflag) {
    if (comm->me == 0)
      error->warning(FLERR,"Cannot count rigid body degrees-of-freedom "
                     "before bodies are fully initialized");
    return 0;
  }

  int tgroupbit = group->bitmask[tgroup];

  // nall = # of point particles in each rigid body
  // mall = # of finite-size particles in each rigid body
  // particles must also be in temperature group

  int *mask = atom->mask;
  int nlocal = atom->nlocal;

  int *ncount = new int[nbody];
  int *mcount = new int[nbody];
  for (int ibody = 0; ibody < nbody; ibody++)
    ncount[ibody] = mcount[ibody] = 0;

  for (int i = 0; i < nlocal; i++)
    if (body[i] >= 0 && mask[i] & tgroupbit) {
      if (extended && eflags[i]) mcount[body[i]]++;
      else ncount[body[i]]++;
    }

  int *nall = new int[nbody];
  int *mall = new int[nbody];
  MPI_Allreduce(ncount,nall,nbody,MPI_INT,MPI_SUM,world);
  MPI_Allreduce(mcount,mall,nbody,MPI_INT,MPI_SUM,world);

  // warn if nall+mall != nrigid for any body included in temperature group

  int flag = 0;
  for (int ibody = 0; ibody < nbody; ibody++) {
    if (nall[ibody]+mall[ibody] > 0 &&
        nall[ibody]+mall[ibody] != nrigid[ibody]) flag = 1;
  }
  if (flag && me == 0)
    error->warning(FLERR,"Computing temperature of portions of rigid bodies");

  // remove appropriate DOFs for each rigid body wholly in temperature group
  // N = # of point particles in body
  // M = # of finite-size particles in body
  // 3d body has 3N + 6M dof to start with
  // 2d body has 2N + 3M dof to start with
  // 3d point-particle body with all non-zero I should have 6 dof, remove 3N-6
  // 3d point-particle body (linear) with a 0 I should have 5 dof, remove 3N-5
  // 2d point-particle body should have 3 dof, remove 2N-3
  // 3d body with any finite-size M should have 6 dof, remove (3N+6M) - 6
  // 2d body with any finite-size M should have 3 dof, remove (2N+3M) - 3

  int n = 0;
  if (domain->dimension == 3) {
    for (int ibody = 0; ibody < nbody; ibody++)
      if (nall[ibody]+mall[ibody] == nrigid[ibody]) {
        n += 3*nall[ibody] + 6*mall[ibody] - 6;
        if (inertia[ibody][0] == 0.0 || inertia[ibody][1] == 0.0 ||
            inertia[ibody][2] == 0.0) n++;
      }
  } else if (domain->dimension == 2) {
    for (int ibody = 0; ibody < nbody; ibody++)
      if (nall[ibody]+mall[ibody] == nrigid[ibody])
        n += 2*nall[ibody] + 3*mall[ibody] - 3;
  }

  delete [] ncount;
  delete [] mcount;
  delete [] nall;
  delete [] mall;

  return n;
}

/* ----------------------------------------------------------------------
   adjust xcm of each rigid body due to box deformation
   called by various fixes that change box size/shape
   flag = 0/1 means map from box to lamda coords or vice versa
------------------------------------------------------------------------- */

void FixRigid::deform(int flag)
{
  if (flag == 0)
    for (int ibody = 0; ibody < nbody; ibody++)
      domain->x2lamda(xcm[ibody],xcm[ibody]);
  else
    for (int ibody = 0; ibody < nbody; ibody++)
      domain->lamda2x(xcm[ibody],xcm[ibody]);
}

/* ----------------------------------------------------------------------
   set space-frame coords and velocity of each atom in each rigid body
   set orientation and rotation of extended particles
   x = Q displace + Xcm, mapped back to periodic box
   v = Vcm + (W cross (x - Xcm))
------------------------------------------------------------------------- */

void FixRigid::set_xv()
{
  int ibody;
  int xbox,ybox,zbox;
  double x0,x1,x2,v0,v1,v2,fc0,fc1,fc2,massone;
  double xy,xz,yz;
  double ione[3],exone[3],eyone[3],ezone[3],vr[6],p[3][3];

  tagint *image = atom->image;
  double **x = atom->x;
  double **v = atom->v;
  double **f = atom->f;
  double *rmass = atom->rmass;
  double *mass = atom->mass;
  int *type = atom->type;
  int nlocal = atom->nlocal;

  double xprd = domain->xprd;
  double yprd = domain->yprd;
  double zprd = domain->zprd;

  if (triclinic) {
    xy = domain->xy;
    xz = domain->xz;
    yz = domain->yz;
  }

  // set x and v of each atom

  for (int i = 0; i < nlocal; i++) {
    if (body[i] < 0) continue;
    ibody = body[i];

    xbox = (image[i] & IMGMASK) - IMGMAX;
    ybox = (image[i] >> IMGBITS & IMGMASK) - IMGMAX;
    zbox = (image[i] >> IMG2BITS) - IMGMAX;

    // save old positions and velocities for virial

    if (evflag) {
      if (triclinic == 0) {
        x0 = x[i][0] + xbox*xprd;
        x1 = x[i][1] + ybox*yprd;
        x2 = x[i][2] + zbox*zprd;
      } else {
        x0 = x[i][0] + xbox*xprd + ybox*xy + zbox*xz;
        x1 = x[i][1] + ybox*yprd + zbox*yz;
        x2 = x[i][2] + zbox*zprd;
      }
      v0 = v[i][0];
      v1 = v[i][1];
      v2 = v[i][2];
    }

    // x = displacement from center-of-mass, based on body orientation
    // v = vcm + omega around center-of-mass

    MathExtra::matvec(ex_space[ibody],ey_space[ibody],
                      ez_space[ibody],displace[i],x[i]);

    v[i][0] = omega[ibody][1]*x[i][2] - omega[ibody][2]*x[i][1] +
      vcm[ibody][0];
    v[i][1] = omega[ibody][2]*x[i][0] - omega[ibody][0]*x[i][2] +
      vcm[ibody][1];
    v[i][2] = omega[ibody][0]*x[i][1] - omega[ibody][1]*x[i][0] +
      vcm[ibody][2];

    // add center of mass to displacement
    // map back into periodic box via xbox,ybox,zbox
    // for triclinic, add in box tilt factors as well

    if (triclinic == 0) {
      x[i][0] += xcm[ibody][0] - xbox*xprd;
      x[i][1] += xcm[ibody][1] - ybox*yprd;
      x[i][2] += xcm[ibody][2] - zbox*zprd;
    } else {
      x[i][0] += xcm[ibody][0] - xbox*xprd - ybox*xy - zbox*xz;
      x[i][1] += xcm[ibody][1] - ybox*yprd - zbox*yz;
      x[i][2] += xcm[ibody][2] - zbox*zprd;
    }

    // virial = unwrapped coords dotted into body constraint force
    // body constraint force = implied force due to v change minus f external
    // assume f does not include forces internal to body
    // 1/2 factor b/c final_integrate contributes other half
    // assume per-atom contribution is due to constraint force on that atom

    if (evflag) {
      if (rmass) massone = rmass[i];
      else massone = mass[type[i]];
      fc0 = massone*(v[i][0] - v0)/dtf - f[i][0];
      fc1 = massone*(v[i][1] - v1)/dtf - f[i][1];
      fc2 = massone*(v[i][2] - v2)/dtf - f[i][2];

      vr[0] = 0.5*x0*fc0;
      vr[1] = 0.5*x1*fc1;
      vr[2] = 0.5*x2*fc2;
      vr[3] = 0.5*x0*fc1;
      vr[4] = 0.5*x0*fc2;
      vr[5] = 0.5*x1*fc2;

      v_tally(1,&i,1.0,vr);
    }
  }

  // set orientation, omega, angmom of each extended particle

  if (extended) {
    double theta_body,theta;
    double *shape,*quatatom,*inertiaatom;

    AtomVecEllipsoid::Bonus *ebonus;
    if (avec_ellipsoid) ebonus = avec_ellipsoid->bonus;
    AtomVecLine::Bonus *lbonus;
    if (avec_line) lbonus = avec_line->bonus;
    AtomVecTri::Bonus *tbonus;
    if (avec_tri) tbonus = avec_tri->bonus;
    double **omega_one = atom->omega;
    double **angmom_one = atom->angmom;
    double **mu = atom->mu;
    int *ellipsoid = atom->ellipsoid;
    int *line = atom->line;
    int *tri = atom->tri;

    for (int i = 0; i < nlocal; i++) {
      if (body[i] < 0) continue;
      ibody = body[i];

      if (eflags[i] & SPHERE) {
        omega_one[i][0] = omega[ibody][0];
        omega_one[i][1] = omega[ibody][1];
        omega_one[i][2] = omega[ibody][2];
      } else if (eflags[i] & ELLIPSOID) {
        shape = ebonus[ellipsoid[i]].shape;
        quatatom = ebonus[ellipsoid[i]].quat;
        MathExtra::quatquat(quat[ibody],orient[i],quatatom);
        MathExtra::qnormalize(quatatom);
        ione[0] = EINERTIA*rmass[i] * (shape[1]*shape[1] + shape[2]*shape[2]);
        ione[1] = EINERTIA*rmass[i] * (shape[0]*shape[0] + shape[2]*shape[2]);
        ione[2] = EINERTIA*rmass[i] * (shape[0]*shape[0] + shape[1]*shape[1]);
        MathExtra::q_to_exyz(quatatom,exone,eyone,ezone);
        MathExtra::omega_to_angmom(omega[ibody],exone,eyone,ezone,ione,
                                   angmom_one[i]);
      } else if (eflags[i] & LINE) {
        if (quat[ibody][3] >= 0.0) theta_body = 2.0*acos(quat[ibody][0]);
        else theta_body = -2.0*acos(quat[ibody][0]);
        theta = orient[i][0] + theta_body;
        while (theta <= MINUSPI) theta += TWOPI;
        while (theta > MY_PI) theta -= TWOPI;
        lbonus[line[i]].theta = theta;
        omega_one[i][0] = omega[ibody][0];
        omega_one[i][1] = omega[ibody][1];
        omega_one[i][2] = omega[ibody][2];
      } else if (eflags[i] & TRIANGLE) {
        inertiaatom = tbonus[tri[i]].inertia;
        quatatom = tbonus[tri[i]].quat;
        MathExtra::quatquat(quat[ibody],orient[i],quatatom);
        MathExtra::qnormalize(quatatom);
        MathExtra::q_to_exyz(quatatom,exone,eyone,ezone);
        MathExtra::omega_to_angmom(omega[ibody],exone,eyone,ezone,
                                   inertiaatom,angmom_one[i]);
      }
      if (eflags[i] & DIPOLE) {
        MathExtra::quat_to_mat(quat[ibody],p);
        MathExtra::matvec(p,dorient[i],mu[i]);
        MathExtra::snormalize3(mu[i][3],mu[i],mu[i]);
      }
    }
  }
}

/* ----------------------------------------------------------------------
   set space-frame velocity of each atom in a rigid body
   set omega and angmom of extended particles
   v = Vcm + (W cross (x - Xcm))
------------------------------------------------------------------------- */

void FixRigid::set_v()
{
  int xbox,ybox,zbox;
  double x0,x1,x2,v0,v1,v2,fc0,fc1,fc2,massone;
  double xy,xz,yz;
  double ione[3],exone[3],eyone[3],ezone[3],delta[3],vr[6];

  double **x = atom->x;
  double **v = atom->v;
  double **f = atom->f;
  double *rmass = atom->rmass;
  double *mass = atom->mass;
  int *type = atom->type;
  tagint *image = atom->image;
  int nlocal = atom->nlocal;

  double xprd = domain->xprd;
  double yprd = domain->yprd;
  double zprd = domain->zprd;
  if (triclinic) {
    xy = domain->xy;
    xz = domain->xz;
    yz = domain->yz;
  }

  // set v of each atom

  for (int i = 0; i < nlocal; i++) {
    if (body[i] < 0) continue;
    const int ibody = body[i];

    MathExtra::matvec(ex_space[ibody],ey_space[ibody],
                      ez_space[ibody],displace[i],delta);

    // save old velocities for virial

    if (evflag) {
      v0 = v[i][0];
      v1 = v[i][1];
      v2 = v[i][2];
    }

    v[i][0] = omega[ibody][1]*delta[2] - omega[ibody][2]*delta[1] +
      vcm[ibody][0];
    v[i][1] = omega[ibody][2]*delta[0] - omega[ibody][0]*delta[2] +
      vcm[ibody][1];
    v[i][2] = omega[ibody][0]*delta[1] - omega[ibody][1]*delta[0] +
      vcm[ibody][2];

    // virial = unwrapped coords dotted into body constraint force
    // body constraint force = implied force due to v change minus f external
    // assume f does not include forces internal to body
    // 1/2 factor b/c initial_integrate contributes other half
    // assume per-atom contribution is due to constraint force on that atom

    if (evflag) {
      if (rmass) massone = rmass[i];
      else massone = mass[type[i]];
      fc0 = massone*(v[i][0] - v0)/dtf - f[i][0];
      fc1 = massone*(v[i][1] - v1)/dtf - f[i][1];
      fc2 = massone*(v[i][2] - v2)/dtf - f[i][2];

      xbox = (image[i] & IMGMASK) - IMGMAX;
      ybox = (image[i] >> IMGBITS & IMGMASK) - IMGMAX;
      zbox = (image[i] >> IMG2BITS) - IMGMAX;

      if (triclinic == 0) {
        x0 = x[i][0] + xbox*xprd;
        x1 = x[i][1] + ybox*yprd;
        x2 = x[i][2] + zbox*zprd;
      } else {
        x0 = x[i][0] + xbox*xprd + ybox*xy + zbox*xz;
        x1 = x[i][1] + ybox*yprd + zbox*yz;
        x2 = x[i][2] + zbox*zprd;
      }

      vr[0] = 0.5*x0*fc0;
      vr[1] = 0.5*x1*fc1;
      vr[2] = 0.5*x2*fc2;
      vr[3] = 0.5*x0*fc1;
      vr[4] = 0.5*x0*fc2;
      vr[5] = 0.5*x1*fc2;

      v_tally(1,&i,1.0,vr);
    }
  }

  // set omega, angmom of each extended particle

  if (extended) {
    double *shape,*quatatom,*inertiaatom;

    AtomVecEllipsoid::Bonus *ebonus;
    if (avec_ellipsoid) ebonus = avec_ellipsoid->bonus;
    AtomVecTri::Bonus *tbonus;
    if (avec_tri) tbonus = avec_tri->bonus;
    double **omega_one = atom->omega;
    double **angmom_one = atom->angmom;
    int *ellipsoid = atom->ellipsoid;
    int *tri = atom->tri;

    for (int i = 0; i < nlocal; i++) {
      if (body[i] < 0) continue;
      const int ibody = body[i];

      if (eflags[i] & SPHERE) {
        omega_one[i][0] = omega[ibody][0];
        omega_one[i][1] = omega[ibody][1];
        omega_one[i][2] = omega[ibody][2];
      } else if (eflags[i] & ELLIPSOID) {
        shape = ebonus[ellipsoid[i]].shape;
        quatatom = ebonus[ellipsoid[i]].quat;
        ione[0] = EINERTIA*rmass[i] * (shape[1]*shape[1] + shape[2]*shape[2]);
        ione[1] = EINERTIA*rmass[i] * (shape[0]*shape[0] + shape[2]*shape[2]);
        ione[2] = EINERTIA*rmass[i] * (shape[0]*shape[0] + shape[1]*shape[1]);
        MathExtra::q_to_exyz(quatatom,exone,eyone,ezone);
        MathExtra::omega_to_angmom(omega[ibody],exone,eyone,ezone,ione,
                                   angmom_one[i]);
      } else if (eflags[i] & LINE) {
        omega_one[i][0] = omega[ibody][0];
        omega_one[i][1] = omega[ibody][1];
        omega_one[i][2] = omega[ibody][2];
      } else if (eflags[i] & TRIANGLE) {
        inertiaatom = tbonus[tri[i]].inertia;
        quatatom = tbonus[tri[i]].quat;
        MathExtra::q_to_exyz(quatatom,exone,eyone,ezone);
        MathExtra::omega_to_angmom(omega[ibody],exone,eyone,ezone,
                                   inertiaatom,angmom_one[i]);
      }
    }
  }
}

/* ----------------------------------------------------------------------
   one-time initialization of static rigid body attributes
   extended flags, masstotal, center-of-mass
   Cartesian and diagonalized inertia tensor
   read per-body attributes from infile if specified
------------------------------------------------------------------------- */

void FixRigid::setup_bodies_static()
{
  int i,ibody;

  // extended = 1 if any particle in a rigid body is finite size
  //              or has a dipole moment

  extended = orientflag = dorientflag = 0;

  AtomVecEllipsoid::Bonus *ebonus;
  if (avec_ellipsoid) ebonus = avec_ellipsoid->bonus;
  AtomVecLine::Bonus *lbonus;
  if (avec_line) lbonus = avec_line->bonus;
  AtomVecTri::Bonus *tbonus;
  if (avec_tri) tbonus = avec_tri->bonus;
  double **mu = atom->mu;
  double *radius = atom->radius;
  double *rmass = atom->rmass;
  double *mass = atom->mass;
  int *ellipsoid = atom->ellipsoid;
  int *line = atom->line;
  int *tri = atom->tri;
  int *type = atom->type;
  int nlocal = atom->nlocal;

  if (atom->radius_flag || atom->ellipsoid_flag || atom->line_flag ||
      atom->tri_flag || atom->mu_flag) {
    int flag = 0;
    for (i = 0; i < nlocal; i++) {
      if (body[i] < 0) continue;
      if (radius && radius[i] > 0.0) flag = 1;
      if (ellipsoid && ellipsoid[i] >= 0) flag = 1;
      if (line && line[i] >= 0) flag = 1;
      if (tri && tri[i] >= 0) flag = 1;
      if (mu && mu[i][3] > 0.0) flag = 1;
    }

    MPI_Allreduce(&flag,&extended,1,MPI_INT,MPI_MAX,world);
  }

  // grow extended arrays and set extended flags for each particle
  // orientflag = 4 if any particle stores ellipsoid or tri orientation
  // orientflag = 1 if any particle stores line orientation
  // dorientflag = 1 if any particle stores dipole orientation

  if (extended) {
    if (atom->ellipsoid_flag) orientflag = 4;
    if (atom->line_flag) orientflag = 1;
    if (atom->tri_flag) orientflag = 4;
    if (atom->mu_flag) dorientflag = 1;
    grow_arrays(atom->nmax);

    for (i = 0; i < nlocal; i++) {
      eflags[i] = 0;
      if (body[i] < 0) continue;

      // set to POINT or SPHERE or ELLIPSOID or LINE

      if (radius && radius[i] > 0.0) {
        eflags[i] |= SPHERE;
        eflags[i] |= OMEGA;
        eflags[i] |= TORQUE;
      } else if (ellipsoid && ellipsoid[i] >= 0) {
        eflags[i] |= ELLIPSOID;
        eflags[i] |= ANGMOM;
        eflags[i] |= TORQUE;
      } else if (line && line[i] >= 0) {
        eflags[i] |= LINE;
        eflags[i] |= OMEGA;
        eflags[i] |= TORQUE;
      } else if (tri && tri[i] >= 0) {
        eflags[i] |= TRIANGLE;
        eflags[i] |= ANGMOM;
        eflags[i] |= TORQUE;
      } else eflags[i] |= POINT;

      // set DIPOLE if atom->mu and mu[3] > 0.0

      if (atom->mu_flag && mu[i][3] > 0.0)
        eflags[i] |= DIPOLE;
    }
  }

  // compute masstotal & center-of-mass of each rigid body
  // error if image flag is not 0 in a non-periodic dim

  double **x = atom->x;
  tagint *image = atom->image;

  int *periodicity = domain->periodicity;
  double xprd = domain->xprd;
  double yprd = domain->yprd;
  double zprd = domain->zprd;
  double xy = domain->xy;
  double xz = domain->xz;
  double yz = domain->yz;

  for (ibody = 0; ibody < nbody; ibody++)
    for (i = 0; i < 6; i++) sum[ibody][i] = 0.0;
  int xbox,ybox,zbox;
  double massone,xunwrap,yunwrap,zunwrap;

  for (i = 0; i < nlocal; i++) {
    if (body[i] < 0) continue;
    ibody = body[i];

    xbox = (image[i] & IMGMASK) - IMGMAX;
    ybox = (image[i] >> IMGBITS & IMGMASK) - IMGMAX;
    zbox = (image[i] >> IMG2BITS) - IMGMAX;
    if (rmass) massone = rmass[i];
    else massone = mass[type[i]];

    if ((xbox && !periodicity[0]) || (ybox && !periodicity[1]) ||
        (zbox && !periodicity[2]))
      error->one(FLERR,"Fix rigid atom has non-zero image flag "
                 "in a non-periodic dimension");

    if (triclinic == 0) {
      xunwrap = x[i][0] + xbox*xprd;
      yunwrap = x[i][1] + ybox*yprd;
      zunwrap = x[i][2] + zbox*zprd;
    } else {
      xunwrap = x[i][0] + xbox*xprd + ybox*xy + zbox*xz;
      yunwrap = x[i][1] + ybox*yprd + zbox*yz;
      zunwrap = x[i][2] + zbox*zprd;
    }

    sum[ibody][0] += xunwrap * massone;
    sum[ibody][1] += yunwrap * massone;
    sum[ibody][2] += zunwrap * massone;
    sum[ibody][3] += massone;
  }

  MPI_Allreduce(sum[0],all[0],6*nbody,MPI_DOUBLE,MPI_SUM,world);

  for (ibody = 0; ibody < nbody; ibody++) {
    masstotal[ibody] = all[ibody][3];
    xcm[ibody][0] = all[ibody][0]/masstotal[ibody];
    xcm[ibody][1] = all[ibody][1]/masstotal[ibody];
    xcm[ibody][2] = all[ibody][2]/masstotal[ibody];
  }

  // overwrite masstotal and center-of-mass with file values
  // inbody[i] = 0/1 if Ith rigid body is initialized by file

  int *inbody;
  if (infile) {
    memory->create(inbody,nbody,"rigid:inbody");
    for (ibody = 0; ibody < nbody; ibody++) inbody[ibody] = 0;
    readfile(0,masstotal,xcm,inbody);
  }

  // set image flags for each rigid body to default values
  // then remap the xcm of each body back into simulation box if needed

  for (ibody = 0; ibody < nbody; ibody++)
    imagebody[ibody] = ((tagint) IMGMAX << IMG2BITS) |
      ((tagint) IMGMAX << IMGBITS) | IMGMAX;

  pre_neighbor();

  // compute 6 moments of inertia of each body in Cartesian reference frame
  // dx,dy,dz = coords relative to center-of-mass
  // symmetric 3x3 inertia tensor stored in Voigt notation as 6-vector

  double dx,dy,dz;

  for (ibody = 0; ibody < nbody; ibody++)
    for (i = 0; i < 6; i++) sum[ibody][i] = 0.0;

  for (i = 0; i < nlocal; i++) {
    if (body[i] < 0) continue;
    ibody = body[i];

    xbox = (image[i] & IMGMASK) - IMGMAX;
    ybox = (image[i] >> IMGBITS & IMGMASK) - IMGMAX;
    zbox = (image[i] >> IMG2BITS) - IMGMAX;

    if (triclinic == 0) {
      xunwrap = x[i][0] + xbox*xprd;
      yunwrap = x[i][1] + ybox*yprd;
      zunwrap = x[i][2] + zbox*zprd;
    } else {
      xunwrap = x[i][0] + xbox*xprd + ybox*xy + zbox*xz;
      yunwrap = x[i][1] + ybox*yprd + zbox*yz;
      zunwrap = x[i][2] + zbox*zprd;
    }

    dx = xunwrap - xcm[ibody][0];
    dy = yunwrap - xcm[ibody][1];
    dz = zunwrap - xcm[ibody][2];

    if (rmass) massone = rmass[i];
    else massone = mass[type[i]];

    sum[ibody][0] += massone * (dy*dy + dz*dz);
    sum[ibody][1] += massone * (dx*dx + dz*dz);
    sum[ibody][2] += massone * (dx*dx + dy*dy);
    sum[ibody][3] -= massone * dy*dz;
    sum[ibody][4] -= massone * dx*dz;
    sum[ibody][5] -= massone * dx*dy;
  }

  // extended particles may contribute extra terms to moments of inertia

  if (extended) {
    double ivec[6];
    double *shape,*quatatom,*inertiaatom;
    double length,theta;

    for (i = 0; i < nlocal; i++) {
      if (body[i] < 0) continue;
      ibody = body[i];
      if (rmass) massone = rmass[i];
      else massone = mass[type[i]];

      if (eflags[i] & SPHERE) {
        sum[ibody][0] += SINERTIA*massone * radius[i]*radius[i];
        sum[ibody][1] += SINERTIA*massone * radius[i]*radius[i];
        sum[ibody][2] += SINERTIA*massone * radius[i]*radius[i];
      } else if (eflags[i] & ELLIPSOID) {
        shape = ebonus[ellipsoid[i]].shape;
        quatatom = ebonus[ellipsoid[i]].quat;
        MathExtra::inertia_ellipsoid(shape,quatatom,massone,ivec);
        sum[ibody][0] += ivec[0];
        sum[ibody][1] += ivec[1];
        sum[ibody][2] += ivec[2];
        sum[ibody][3] += ivec[3];
        sum[ibody][4] += ivec[4];
        sum[ibody][5] += ivec[5];
      } else if (eflags[i] & LINE) {
        length = lbonus[line[i]].length;
        theta = lbonus[line[i]].theta;
        MathExtra::inertia_line(length,theta,massone,ivec);
        sum[ibody][0] += ivec[0];
        sum[ibody][1] += ivec[1];
        sum[ibody][2] += ivec[2];
        sum[ibody][3] += ivec[3];
        sum[ibody][4] += ivec[4];
        sum[ibody][5] += ivec[5];
      } else if (eflags[i] & TRIANGLE) {
        inertiaatom = tbonus[tri[i]].inertia;
        quatatom = tbonus[tri[i]].quat;
        MathExtra::inertia_triangle(inertiaatom,quatatom,massone,ivec);
        sum[ibody][0] += ivec[0];
        sum[ibody][1] += ivec[1];
        sum[ibody][2] += ivec[2];
        sum[ibody][3] += ivec[3];
        sum[ibody][4] += ivec[4];
        sum[ibody][5] += ivec[5];
      }
    }
  }

  MPI_Allreduce(sum[0],all[0],6*nbody,MPI_DOUBLE,MPI_SUM,world);

  // overwrite Cartesian inertia tensor with file values

  if (infile) readfile(1,NULL,all,inbody);

  // diagonalize inertia tensor for each body via Jacobi rotations
  // inertia = 3 eigenvalues = principal moments of inertia
  // evectors and exzy_space = 3 evectors = principal axes of rigid body

  int ierror;
  double cross[3];
  double tensor[3][3],evectors[3][3];

  for (ibody = 0; ibody < nbody; ibody++) {
    tensor[0][0] = all[ibody][0];
    tensor[1][1] = all[ibody][1];
    tensor[2][2] = all[ibody][2];
    tensor[1][2] = tensor[2][1] = all[ibody][3];
    tensor[0][2] = tensor[2][0] = all[ibody][4];
    tensor[0][1] = tensor[1][0] = all[ibody][5];

    ierror = MathExtra::jacobi(tensor,inertia[ibody],evectors);
    if (ierror) error->all(FLERR,
                           "Insufficient Jacobi rotations for rigid body");

    ex_space[ibody][0] = evectors[0][0];
    ex_space[ibody][1] = evectors[1][0];
    ex_space[ibody][2] = evectors[2][0];
    ey_space[ibody][0] = evectors[0][1];
    ey_space[ibody][1] = evectors[1][1];
    ey_space[ibody][2] = evectors[2][1];
    ez_space[ibody][0] = evectors[0][2];
    ez_space[ibody][1] = evectors[1][2];
    ez_space[ibody][2] = evectors[2][2];

    // if any principal moment < scaled EPSILON, set to 0.0

    double max;
    max = MAX(inertia[ibody][0],inertia[ibody][1]);
    max = MAX(max,inertia[ibody][2]);

    if (inertia[ibody][0] < EPSILON*max) inertia[ibody][0] = 0.0;
    if (inertia[ibody][1] < EPSILON*max) inertia[ibody][1] = 0.0;
    if (inertia[ibody][2] < EPSILON*max) inertia[ibody][2] = 0.0;

    // enforce 3 evectors as a right-handed coordinate system
    // flip 3rd vector if needed

    MathExtra::cross3(ex_space[ibody],ey_space[ibody],cross);
    if (MathExtra::dot3(cross,ez_space[ibody]) < 0.0)
      MathExtra::negate3(ez_space[ibody]);

    // create initial quaternion

    MathExtra::exyz_to_q(ex_space[ibody],ey_space[ibody],ez_space[ibody],
                         quat[ibody]);
  }

  // displace = initial atom coords in basis of principal axes
  // set displace = 0.0 for atoms not in any rigid body
  // for extended particles, set their orientation wrt to rigid body

  double qc[4],delta[3];
  double *quatatom;
  double theta_body;

  for (i = 0; i < nlocal; i++) {
    if (body[i] < 0) {
      displace[i][0] = displace[i][1] = displace[i][2] = 0.0;
      continue;
    }

    ibody = body[i];

    xbox = (image[i] & IMGMASK) - IMGMAX;
    ybox = (image[i] >> IMGBITS & IMGMASK) - IMGMAX;
    zbox = (image[i] >> IMG2BITS) - IMGMAX;

    if (triclinic == 0) {
      xunwrap = x[i][0] + xbox*xprd;
      yunwrap = x[i][1] + ybox*yprd;
      zunwrap = x[i][2] + zbox*zprd;
    } else {
      xunwrap = x[i][0] + xbox*xprd + ybox*xy + zbox*xz;
      yunwrap = x[i][1] + ybox*yprd + zbox*yz;
      zunwrap = x[i][2] + zbox*zprd;
    }

    delta[0] = xunwrap - xcm[ibody][0];
    delta[1] = yunwrap - xcm[ibody][1];
    delta[2] = zunwrap - xcm[ibody][2];
    MathExtra::transpose_matvec(ex_space[ibody],ey_space[ibody],
                                ez_space[ibody],delta,displace[i]);

    if (extended) {
      if (eflags[i] & ELLIPSOID) {
        quatatom = ebonus[ellipsoid[i]].quat;
        MathExtra::qconjugate(quat[ibody],qc);
        MathExtra::quatquat(qc,quatatom,orient[i]);
        MathExtra::qnormalize(orient[i]);
      } else if (eflags[i] & LINE) {
        if (quat[ibody][3] >= 0.0) theta_body = 2.0*acos(quat[ibody][0]);
        else theta_body = -2.0*acos(quat[ibody][0]);
        orient[i][0] = lbonus[line[i]].theta - theta_body;
        while (orient[i][0] <= MINUSPI) orient[i][0] += TWOPI;
        while (orient[i][0] > MY_PI) orient[i][0] -= TWOPI;
        if (orientflag == 4) orient[i][1] = orient[i][2] = orient[i][3] = 0.0;
      } else if (eflags[i] & TRIANGLE) {
        quatatom = tbonus[tri[i]].quat;
        MathExtra::qconjugate(quat[ibody],qc);
        MathExtra::quatquat(qc,quatatom,orient[i]);
        MathExtra::qnormalize(orient[i]);
      } else if (orientflag == 4) {
        orient[i][0] = orient[i][1] = orient[i][2] = orient[i][3] = 0.0;
      } else if (orientflag == 1)
        orient[i][0] = 0.0;

      if (eflags[i] & DIPOLE) {
        MathExtra::transpose_matvec(ex_space[ibody],ey_space[ibody],
                                    ez_space[ibody],mu[i],dorient[i]);
        MathExtra::snormalize3(mu[i][3],dorient[i],dorient[i]);
      } else if (dorientflag)
        dorient[i][0] = dorient[i][1] = dorient[i][2] = 0.0;
    }
  }

  // test for valid principal moments & axes
  // recompute moments of inertia around new axes
  // 3 diagonal moments should equal principal moments
  // 3 off-diagonal moments should be 0.0
  // extended particles may contribute extra terms to moments of inertia

  for (ibody = 0; ibody < nbody; ibody++)
    for (i = 0; i < 6; i++) sum[ibody][i] = 0.0;

  for (i = 0; i < nlocal; i++) {
    if (body[i] < 0) continue;
    ibody = body[i];
    if (rmass) massone = rmass[i];
    else massone = mass[type[i]];

    sum[ibody][0] += massone *
      (displace[i][1]*displace[i][1] + displace[i][2]*displace[i][2]);
    sum[ibody][1] += massone *
      (displace[i][0]*displace[i][0] + displace[i][2]*displace[i][2]);
    sum[ibody][2] += massone *
      (displace[i][0]*displace[i][0] + displace[i][1]*displace[i][1]);
    sum[ibody][3] -= massone * displace[i][1]*displace[i][2];
    sum[ibody][4] -= massone * displace[i][0]*displace[i][2];
    sum[ibody][5] -= massone * displace[i][0]*displace[i][1];
  }

  if (extended) {
    double ivec[6];
    double *shape,*inertiaatom;
    double length;

    for (i = 0; i < nlocal; i++) {
      if (body[i] < 0) continue;
      ibody = body[i];
      if (rmass) massone = rmass[i];
      else massone = mass[type[i]];

      if (eflags[i] & SPHERE) {
        sum[ibody][0] += SINERTIA*massone * radius[i]*radius[i];
        sum[ibody][1] += SINERTIA*massone * radius[i]*radius[i];
        sum[ibody][2] += SINERTIA*massone * radius[i]*radius[i];
      } else if (eflags[i] & ELLIPSOID) {
        shape = ebonus[ellipsoid[i]].shape;
        MathExtra::inertia_ellipsoid(shape,orient[i],massone,ivec);
        sum[ibody][0] += ivec[0];
        sum[ibody][1] += ivec[1];
        sum[ibody][2] += ivec[2];
        sum[ibody][3] += ivec[3];
        sum[ibody][4] += ivec[4];
        sum[ibody][5] += ivec[5];
      } else if (eflags[i] & LINE) {
        length = lbonus[line[i]].length;
        MathExtra::inertia_line(length,orient[i][0],massone,ivec);
        sum[ibody][0] += ivec[0];
        sum[ibody][1] += ivec[1];
        sum[ibody][2] += ivec[2];
        sum[ibody][3] += ivec[3];
        sum[ibody][4] += ivec[4];
        sum[ibody][5] += ivec[5];
      } else if (eflags[i] & TRIANGLE) {
        inertiaatom = tbonus[tri[i]].inertia;
        MathExtra::inertia_triangle(inertiaatom,orient[i],massone,ivec);
        sum[ibody][0] += ivec[0];
        sum[ibody][1] += ivec[1];
        sum[ibody][2] += ivec[2];
        sum[ibody][3] += ivec[3];
        sum[ibody][4] += ivec[4];
        sum[ibody][5] += ivec[5];
      }
    }
  }

  MPI_Allreduce(sum[0],all[0],6*nbody,MPI_DOUBLE,MPI_SUM,world);

  // error check that re-computed momemts of inertia match diagonalized ones
  // do not do test for bodies with params read from infile

  double norm;
  for (ibody = 0; ibody < nbody; ibody++) {
    if (infile && inbody[ibody]) continue;
    if (inertia[ibody][0] == 0.0) {
      if (fabs(all[ibody][0]) > TOLERANCE)
        error->all(FLERR,"Fix rigid: Bad principal moments");
    } else {
      if (fabs((all[ibody][0]-inertia[ibody][0])/inertia[ibody][0]) >
          TOLERANCE) error->all(FLERR,"Fix rigid: Bad principal moments");
    }
    if (inertia[ibody][1] == 0.0) {
      if (fabs(all[ibody][1]) > TOLERANCE)
        error->all(FLERR,"Fix rigid: Bad principal moments");
    } else {
      if (fabs((all[ibody][1]-inertia[ibody][1])/inertia[ibody][1]) >
          TOLERANCE) error->all(FLERR,"Fix rigid: Bad principal moments");
    }
    if (inertia[ibody][2] == 0.0) {
      if (fabs(all[ibody][2]) > TOLERANCE)
        error->all(FLERR,"Fix rigid: Bad principal moments");
    } else {
      if (fabs((all[ibody][2]-inertia[ibody][2])/inertia[ibody][2]) >
          TOLERANCE) error->all(FLERR,"Fix rigid: Bad principal moments");
    }
    norm = (inertia[ibody][0] + inertia[ibody][1] + inertia[ibody][2]) / 3.0;
    if (fabs(all[ibody][3]/norm) > TOLERANCE ||
        fabs(all[ibody][4]/norm) > TOLERANCE ||
        fabs(all[ibody][5]/norm) > TOLERANCE)
      error->all(FLERR,"Fix rigid: Bad principal moments");
  }

  if (infile) memory->destroy(inbody);
}

/* ----------------------------------------------------------------------
   one-time initialization of dynamic rigid body attributes
   Vcm and angmom, computed explicitly from constituent particles
   even if wrong for overlapping particles, is OK,
     since is just setting initial time=0 Vcm and angmom of the body
     which can be estimated value
------------------------------------------------------------------------- */

void FixRigid::setup_bodies_dynamic()
{
  int i,n,ibody;
  double massone,radone;

  // vcm = velocity of center-of-mass of each rigid body
  // angmom = angular momentum of each rigid body

  double **x = atom->x;
  double **v = atom->v;
  double *rmass = atom->rmass;
  double *mass = atom->mass;
  tagint *image = atom->image;
  int *type = atom->type;
  int nlocal = atom->nlocal;

  double dx,dy,dz;
  double unwrap[3];

  for (ibody = 0; ibody < nbody; ibody++)
    for (i = 0; i < 6; i++) sum[ibody][i] = 0.0;

  for (i = 0; i < nlocal; i++) {
    if (body[i] < 0) continue;
    ibody = body[i];

    if (rmass) massone = rmass[i];
    else massone = mass[type[i]];

    sum[ibody][0] += v[i][0] * massone;
    sum[ibody][1] += v[i][1] * massone;
    sum[ibody][2] += v[i][2] * massone;

    domain->unmap(x[i],image[i],unwrap);
    dx = unwrap[0] - xcm[ibody][0];
    dy = unwrap[1] - xcm[ibody][1];
    dz = unwrap[2] - xcm[ibody][2];

    sum[ibody][3] += dy * massone*v[i][2] - dz * massone*v[i][1];
    sum[ibody][4] += dz * massone*v[i][0] - dx * massone*v[i][2];
    sum[ibody][5] += dx * massone*v[i][1] - dy * massone*v[i][0];
  }

  // extended particles add their rotation to angmom of body

  if (extended) {
    AtomVecLine::Bonus *lbonus;
    if (avec_line) lbonus = avec_line->bonus;
    double **omega_one = atom->omega;
    double **angmom_one = atom->angmom;
    double *radius = atom->radius;
    int *line = atom->line;

    for (i = 0; i < nlocal; i++) {
      if (body[i] < 0) continue;
      ibody = body[i];

      if (eflags[i] & OMEGA) {
        if (eflags[i] & SPHERE) {
          radone = radius[i];
          sum[ibody][3] += SINERTIA*rmass[i] * radone*radone * omega_one[i][0];
          sum[ibody][4] += SINERTIA*rmass[i] * radone*radone * omega_one[i][1];
          sum[ibody][5] += SINERTIA*rmass[i] * radone*radone * omega_one[i][2];
        } else if (eflags[i] & LINE) {
          radone = lbonus[line[i]].length;
          sum[ibody][5] += LINERTIA*rmass[i] * radone*radone * omega_one[i][2];
        }
      }
      if (eflags[i] & ANGMOM) {
        sum[ibody][3] += angmom_one[i][0];
        sum[ibody][4] += angmom_one[i][1];
        sum[ibody][5] += angmom_one[i][2];
      }
    }
  }

  MPI_Allreduce(sum[0],all[0],6*nbody,MPI_DOUBLE,MPI_SUM,world);

  // normalize velocity of COM

  for (ibody = 0; ibody < nbody; ibody++) {
    vcm[ibody][0] = all[ibody][0]/masstotal[ibody];
    vcm[ibody][1] = all[ibody][1]/masstotal[ibody];
    vcm[ibody][2] = all[ibody][2]/masstotal[ibody];
    angmom[ibody][0] = all[ibody][3];
    angmom[ibody][1] = all[ibody][4];
    angmom[ibody][2] = all[ibody][5];
  }
}

/* ----------------------------------------------------------------------
   read per rigid body info from user-provided file
   which = 0 to read total mass and center-of-mass, store in vec and array
   which = 1 to read 6 moments of inertia, store in array
   flag inbody = 0 for bodies whose info is read from file
   nlines = # of lines of rigid body info
   one line = rigid-ID mass xcm ycm zcm ixx iyy izz ixy ixz iyz
------------------------------------------------------------------------- */

void FixRigid::readfile(int which, double *vec, double **array, int *inbody)
{
  int i,j,m,nchunk,id,eofflag;
  int nlines;
  FILE *fp;
  char *eof,*start,*next,*buf;
  char line[MAXLINE];

  if (me == 0) {
    fp = fopen(infile,"r");
    if (fp == NULL) {
      char str[128];
      sprintf(str,"Cannot open fix rigid infile %s",infile);
      error->one(FLERR,str);
    }

    while (1) {
      eof = fgets(line,MAXLINE,fp);
      if (eof == NULL) error->one(FLERR,"Unexpected end of fix rigid file");
      start = &line[strspn(line," \t\n\v\f\r")];
      if (*start != '\0' && *start != '#') break;
    }

    sscanf(line,"%d",&nlines);
  }

  MPI_Bcast(&nlines,1,MPI_INT,0,world);
  if (nlines == 0) error->all(FLERR,"Fix rigid file has no lines");

  char *buffer = new char[CHUNK*MAXLINE];
  char **values = new char*[ATTRIBUTE_PERBODY];

  int nread = 0;
  while (nread < nlines) {
    nchunk = MIN(nlines-nread,CHUNK);
    eofflag = comm->read_lines_from_file(fp,nchunk,MAXLINE,buffer);
    if (eofflag) error->all(FLERR,"Unexpected end of fix rigid file");

    buf = buffer;
    next = strchr(buf,'\n');
    *next = '\0';
    int nwords = atom->count_words(buf);
    *next = '\n';

    if (nwords != ATTRIBUTE_PERBODY)
      error->all(FLERR,"Incorrect rigid body format in fix rigid file");

    // loop over lines of rigid body attributes
    // tokenize the line into values
    // id = rigid body ID
    // use ID as-is for SINGLE, as mol-ID for MOLECULE, as-is for GROUP
    // for which = 0, store mass/com in vec/array
    // for which = 1, store interia tensor array, invert 3,4,5 values to Voigt

    for (int i = 0; i < nchunk; i++) {
      next = strchr(buf,'\n');

      values[0] = strtok(buf," \t\n\r\f");
      for (j = 1; j < nwords; j++)
        values[j] = strtok(NULL," \t\n\r\f");

      id = atoi(values[0]);
      if (rstyle == MOLECULE) {
        if (id <= 0 || id > maxmol)
          error->all(FLERR,"Invalid rigid body ID in fix rigid file");
        id = mol2body[id];
      } else id--;

      if (id < 0 || id >= nbody)
        error->all(FLERR,"Invalid rigid body ID in fix rigid file");
      inbody[id] = 1;

      if (which == 0) {
        vec[id] = atof(values[1]);
        array[id][0] = atof(values[2]);
        array[id][1] = atof(values[3]);
        array[id][2] = atof(values[4]);
      } else {
        array[id][0] = atof(values[5]);
        array[id][1] = atof(values[6]);
        array[id][2] = atof(values[7]);
        array[id][3] = atof(values[10]);
        array[id][4] = atof(values[9]);
        array[id][5] = atof(values[8]);
      }

      buf = next + 1;
    }

    nread += nchunk;
  }

  if (me == 0) fclose(fp);

  delete [] buffer;
  delete [] values;
}

/* ----------------------------------------------------------------------
   write out restart info for mass, COM, inertia tensor to file
   identical format to infile option, so info can be read in when restarting
   only proc 0 writes list of global bodies to file
------------------------------------------------------------------------- */

void FixRigid::write_restart_file(char *file)
{
  if (me) return;

  char outfile[128];
  sprintf(outfile,"%s.rigid",file);
  FILE *fp = fopen(outfile,"w");
  if (fp == NULL) {
    char str[128];
    sprintf(str,"Cannot open fix rigid restart file %s",outfile);
    error->one(FLERR,str);
  }

  fprintf(fp,"# fix rigid mass, COM, inertia tensor info for "
          "%d bodies on timestep " BIGINT_FORMAT "\n\n",
          nbody,update->ntimestep);
  fprintf(fp,"%d\n",nbody);

  // compute I tensor against xyz axes from diagonalized I and current quat
  // Ispace = P Idiag P_transpose
  // P is stored column-wise in exyz_space

  double p[3][3],pdiag[3][3],ispace[3][3];

  int id;
  for (int i = 0; i < nbody; i++) {
    if (rstyle == SINGLE || rstyle == GROUP) id = i;
    else id = body2mol[i];

    MathExtra::col2mat(ex_space[i],ey_space[i],ez_space[i],p);
    MathExtra::times3_diag(p,inertia[i],pdiag);
    MathExtra::times3_transpose(pdiag,p,ispace);

    fprintf(fp,"%d %-1.16e %-1.16e %-1.16e %-1.16e "
            "%-1.16e %-1.16e %-1.16e %-1.16e %-1.16e %-1.16e\n",
            id,masstotal[i],xcm[i][0],xcm[i][1],xcm[i][2],
            ispace[0][0],ispace[1][1],ispace[2][2],
            ispace[0][1],ispace[0][2],ispace[1][2]);
  }

  fclose(fp);
}

/* ----------------------------------------------------------------------
   memory usage of local atom-based arrays
------------------------------------------------------------------------- */

double FixRigid::memory_usage()
{
  int nmax = atom->nmax;
  double bytes = nmax * sizeof(int);
  bytes += nmax*3 * sizeof(double);
  bytes += maxvatom*6 * sizeof(double);    // vatom
  if (extended) {
    bytes += nmax * sizeof(int);
    if (orientflag) bytes = nmax*orientflag * sizeof(double);
    if (dorientflag) bytes = nmax*3 * sizeof(double);
  }
  return bytes;
}

/* ----------------------------------------------------------------------
   allocate local atom-based arrays
------------------------------------------------------------------------- */

void FixRigid::grow_arrays(int nmax)
{
  memory->grow(body,nmax,"rigid:body");
  memory->grow(displace,nmax,3,"rigid:displace");
  if (extended) {
    memory->grow(eflags,nmax,"rigid:eflags");
    if (orientflag) memory->grow(orient,nmax,orientflag,"rigid:orient");
    if (dorientflag) memory->grow(dorient,nmax,3,"rigid:dorient");
  }
}

/* ----------------------------------------------------------------------
   copy values within local atom-based arrays
------------------------------------------------------------------------- */

void FixRigid::copy_arrays(int i, int j, int delflag)
{
  body[j] = body[i];
  displace[j][0] = displace[i][0];
  displace[j][1] = displace[i][1];
  displace[j][2] = displace[i][2];
  if (extended) {
    eflags[j] = eflags[i];
    for (int k = 0; k < orientflag; k++)
      orient[j][k] = orient[i][k];
    if (dorientflag) {
      dorient[j][0] = dorient[i][0];
      dorient[j][1] = dorient[i][1];
      dorient[j][2] = dorient[i][2];
    }
  }
}

/* ----------------------------------------------------------------------
   initialize one atom's array values, called when atom is created
------------------------------------------------------------------------- */

void FixRigid::set_arrays(int i)
{
  body[i] = -1;
  displace[i][0] = 0.0;
  displace[i][1] = 0.0;
  displace[i][2] = 0.0;
}

/* ----------------------------------------------------------------------
   pack values in local atom-based arrays for exchange with another proc
------------------------------------------------------------------------- */

int FixRigid::pack_exchange(int i, double *buf)
{
  buf[0] = body[i];
  buf[1] = displace[i][0];
  buf[2] = displace[i][1];
  buf[3] = displace[i][2];
  if (!extended) return 4;

  int m = 4;
  buf[m++] = eflags[i];
  for (int j = 0; j < orientflag; j++)
    buf[m++] = orient[i][j];
  if (dorientflag) {
    buf[m++] = dorient[i][0];
    buf[m++] = dorient[i][1];
    buf[m++] = dorient[i][2];
  }
  return m;
}

/* ----------------------------------------------------------------------
   unpack values in local atom-based arrays from exchange with another proc
------------------------------------------------------------------------- */

int FixRigid::unpack_exchange(int nlocal, double *buf)
{
  body[nlocal] = static_cast<int> (buf[0]);
  displace[nlocal][0] = buf[1];
  displace[nlocal][1] = buf[2];
  displace[nlocal][2] = buf[3];
  if (!extended) return 4;

  int m = 4;
  eflags[nlocal] = static_cast<int> (buf[m++]);
  for (int j = 0; j < orientflag; j++)
    orient[nlocal][j] = buf[m++];
  if (dorientflag) {
    dorient[nlocal][0] = buf[m++];
    dorient[nlocal][1] = buf[m++];
    dorient[nlocal][2] = buf[m++];
  }
  return m;
}

/* ---------------------------------------------------------------------- */

void FixRigid::reset_dt()
{
  dtv = update->dt;
  dtf = 0.5 * update->dt * force->ftm2v;
  dtq = 0.5 * update->dt;
}

/* ----------------------------------------------------------------------
   zero linear momentum of each rigid body
   set Vcm to 0.0, then reset velocities of particles via set_v()
------------------------------------------------------------------------- */

void FixRigid::zero_momentum()
{
  for (int ibody = 0; ibody < nbody; ibody++)
    vcm[ibody][0] = vcm[ibody][1] = vcm[ibody][2] = 0.0;

  evflag = 0;
  set_v();
}

/* ----------------------------------------------------------------------
   zero angular momentum of each rigid body
   set angmom/omega to 0.0, then reset velocities of particles via set_v()
------------------------------------------------------------------------- */

void FixRigid::zero_rotation()
{
  for (int ibody = 0; ibody < nbody; ibody++) {
    angmom[ibody][0] = angmom[ibody][1] = angmom[ibody][2] = 0.0;
    omega[ibody][0] = omega[ibody][1] = omega[ibody][2] = 0.0;
  }

  evflag = 0;
  set_v();
}

/* ----------------------------------------------------------------------
   return temperature of collection of rigid bodies
   non-active DOF are removed by fflag/tflag and in tfactor
------------------------------------------------------------------------- */

double FixRigid::compute_scalar()
{
  double wbody[3],rot[3][3];

  double t = 0.0;

  for (int i = 0; i < nbody; i++) {
    t += masstotal[i] * (fflag[i][0]*vcm[i][0]*vcm[i][0] +
                         fflag[i][1]*vcm[i][1]*vcm[i][1] +
                             fflag[i][2]*vcm[i][2]*vcm[i][2]);

    // wbody = angular velocity in body frame

    MathExtra::quat_to_mat(quat[i],rot);
    MathExtra::transpose_matvec(rot,angmom[i],wbody);
    if (inertia[i][0] == 0.0) wbody[0] = 0.0;
    else wbody[0] /= inertia[i][0];
    if (inertia[i][1] == 0.0) wbody[1] = 0.0;
    else wbody[1] /= inertia[i][1];
    if (inertia[i][2] == 0.0) wbody[2] = 0.0;
    else wbody[2] /= inertia[i][2];

    t += tflag[i][0]*inertia[i][0]*wbody[0]*wbody[0] +
      tflag[i][1]*inertia[i][1]*wbody[1]*wbody[1] +
      tflag[i][2]*inertia[i][2]*wbody[2]*wbody[2];
  }

  t *= tfactor;
  return t;
}

/* ---------------------------------------------------------------------- */

void *FixRigid::extract(const char *str, int &dim)
{
  if (strcmp(str,"body") == 0) {
    dim = 1;
    return body;
  }
  if (strcmp(str,"masstotal") == 0) {
    dim = 1;
    return masstotal;
  }
  if (strcmp(str,"t_target") == 0) {
    dim = 0;
    return &t_target;
  }

  return NULL;
}

/* ----------------------------------------------------------------------
   return translational KE for all rigid bodies
   KE = 1/2 M Vcm^2
------------------------------------------------------------------------- */

double FixRigid::extract_ke()
{
  double ke = 0.0;
  for (int i = 0; i < nbody; i++)
    ke += masstotal[i] *
      (vcm[i][0]*vcm[i][0] + vcm[i][1]*vcm[i][1] + vcm[i][2]*vcm[i][2]);

  return 0.5*ke;
}

/* ----------------------------------------------------------------------
   return rotational KE for all rigid bodies
   Erotational = 1/2 I wbody^2
------------------------------------------------------------------------- */

double FixRigid::extract_erotational()
{
  double wbody[3],rot[3][3];

  double erotate = 0.0;
  for (int i = 0; i < nbody; i++) {

    // wbody = angular velocity in body frame

    MathExtra::quat_to_mat(quat[i],rot);
    MathExtra::transpose_matvec(rot,angmom[i],wbody);
    if (inertia[i][0] == 0.0) wbody[0] = 0.0;
    else wbody[0] /= inertia[i][0];
    if (inertia[i][1] == 0.0) wbody[1] = 0.0;
    else wbody[1] /= inertia[i][1];
    if (inertia[i][2] == 0.0) wbody[2] = 0.0;
    else wbody[2] /= inertia[i][2];

    erotate += inertia[i][0]*wbody[0]*wbody[0] +
      inertia[i][1]*wbody[1]*wbody[1] + inertia[i][2]*wbody[2]*wbody[2];
  }

  return 0.5*erotate;
}

/* ----------------------------------------------------------------------
   return attributes of a rigid body
   15 values per body
   xcm = 0,1,2; vcm = 3,4,5; fcm = 6,7,8; torque = 9,10,11; image = 12,13,14
------------------------------------------------------------------------- */

double FixRigid::compute_array(int i, int j)
{
  if (j < 3) return xcm[i][j];
  if (j < 6) return vcm[i][j-3];
  if (j < 9) return fcm[i][j-6];
  if (j < 12) return torque[i][j-9];
  if (j == 12) return (imagebody[i] & IMGMASK) - IMGMAX;
  if (j == 13) return (imagebody[i] >> IMGBITS & IMGMASK) - IMGMAX;
  return (imagebody[i] >> IMG2BITS) - IMGMAX;
}
