diff --git a/src/RIGID/fix_rigid_small.cpp b/src/RIGID/fix_rigid_small.cpp
index bd7c18145..dba76f60d 100644
--- a/src/RIGID/fix_rigid_small.cpp
+++ b/src/RIGID/fix_rigid_small.cpp
@@ -1,2663 +1,2663 @@
 /* ----------------------------------------------------------------------
    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.
 ------------------------------------------------------------------------- */
 
 #include "math.h"
 #include "stdio.h"
 #include "stdlib.h"
 #include "string.h"
 #include "fix_rigid_small.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 "force.h"
 #include "output.h"
 #include "random_mars.h"
 #include "math_const.h"
 #include "memory.h"
 #include "error.h"
 
 using namespace LAMMPS_NS;
 using namespace FixConst;
 using namespace MathConst;
 
 // allocate space for static class variable
 
 FixRigidSmall *FixRigidSmall::frsptr;
 
 #define MAXLINE 256
 #define CHUNK 1024
 #define ATTRIBUTE_PERBODY 11
 
 #define TOLERANCE 1.0e-6
 #define EPSILON 1.0e-7
 #define BIG 1.0e20
 
 #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
 
 #define DELTA_BODY 10000
 
 enum{FULL_BODY,INITIAL,FINAL,FORCE_TORQUE,VCM_ANGMOM,XCM_MASS,ITENSOR,DOF};
 
 /* ---------------------------------------------------------------------- */
 
 FixRigidSmall::FixRigidSmall(LAMMPS *lmp, int narg, char **arg) :
   Fix(lmp, narg, arg)
 {
   int i,ibody;
 
   scalar_flag = 1;
   extscalar = 0;
   global_freq = 1;
   time_integrate = 1;
   rigid_flag = 1;
   virial_flag = 1;
   create_attribute = 1;
 
   MPI_Comm_rank(world,&me);
   MPI_Comm_size(world,&nprocs);
 
   // perform initial allocation of atom-based arrays
   // register with Atom class
 
   extended = orientflag = dorientflag = 0;
   bodyown = NULL;
   bodytag = NULL;
   atom2body = NULL;
   displace = NULL;
   eflags = NULL;
   orient = NULL;
   dorient = NULL;
   grow_arrays(atom->nmax);
   atom->add_callback(0);
 
   // parse args for rigid body specification
 
   if (narg < 4) error->all(FLERR,"Illegal fix rigid/small command");
   if (strcmp(arg[3],"molecule") != 0) 
     error->all(FLERR,"Illegal fix rigid/small command");
 
   // parse optional args
 
   int seed;
   langflag = 0;
   
   int iarg = 4;
   while (iarg < narg) {
     if (strcmp(arg[iarg],"langevin") == 0) {
       if (iarg+5 > narg) error->all(FLERR,"Illegal fix rigid/small command");
       if (strcmp(style,"rigid/small") != 0)
         error->all(FLERR,"Illegal fix rigid/small command");
       langflag = 1;
       t_start = atof(arg[iarg+1]);
       t_stop = atof(arg[iarg+2]);
       t_period = atof(arg[iarg+3]);
       seed = atoi(arg[iarg+4]);
       if (t_period <= 0.0)
         error->all(FLERR,"Fix rigid/small langevin period must be > 0.0");
       if (seed <= 0) error->all(FLERR,"Illegal fix rigid/small command");
       iarg += 5;
     } else error->all(FLERR,"Illegal fix rigid/small command");
   }
 
   // create rigid bodies based on molecule ID
   // sets bodytag for owned atoms
   // body attributes are computed later by setup_bodies()
 
   if (atom->molecule_flag == 0)
     error->all(FLERR,"Fix rigid/small requires atom attribute molecule");
 
   create_bodies();
 
   // set nlocal_body and allocate bodies I own
 
   int *tag = atom->tag;
   int nlocal = atom->nlocal;
 
   nlocal_body = nghost_body = 0;
   for (i = 0; i < nlocal; i++)
     if (bodytag[i] == tag[i]) nlocal_body++;
 
   nmax_body = 0;
   while (nmax_body < nlocal_body) nmax_body += DELTA_BODY;
   body = (Body *) memory->smalloc(nmax_body*sizeof(Body),
                                   "rigid/small:body");
 
   // set bodyown for owned atoms
 
   nlocal_body = 0;
   for (i = 0; i < nlocal; i++)
     if (bodytag[i] == tag[i]) {
       body[nlocal_body].ilocal = i;
       bodyown[i] = nlocal_body++;
     } else bodyown[i] = -1;
 
   // bodysize = sizeof(Body) in doubles
 
   bodysize = sizeof(Body)/sizeof(double);
   if (bodysize*sizeof(double) != sizeof(Body)) bodysize++;
 
   // set max comm sizes needed by this fix
 
   comm_forward = 1 + bodysize;
   comm_reverse = 6;
 
   // 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;
 
   // 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");
 
   // print statistics
 
   int one = 0;
   bigint atomone = 0;
   for (int i = 0; i < nlocal; i++) {
     if (bodyown[i] >= 0) one++;
     if (bodytag[i] > 0) atomone++;
   }
   MPI_Allreduce(&one,&nbody,1,MPI_INT,MPI_SUM,world);
   bigint atomall;
   MPI_Allreduce(&atomone,&atomall,1,MPI_LMP_BIGINT,MPI_SUM,world);
   if (nbody == 0) error->all(FLERR,"No rigid bodies defined");
 
   if (me == 0) {
     if (screen) {
       fprintf(screen,"%d rigid bodies with " BIGINT_FORMAT " atoms\n",
               nbody,atomall);
       fprintf(screen,"  %g = max distance from body owner to body atom\n",
               maxextent);
     }
     if (logfile) {
       fprintf(logfile,"%d rigid bodies with " BIGINT_FORMAT " atoms\n",
               nbody,atomall);
       fprintf(logfile,"  %g = max distance from body owner to body atom\n",
               maxextent);
     }
   }
 
   // initialize Marsaglia RNG with processor-unique seed
 
   maxlang = 0;
   langextra = NULL;
   random = NULL;
   if (langflag) random = new RanMars(lmp,seed + comm->me);
 
   // firstflag = 1 triggers one-time initialization of rigid body attributes
 
   firstflag = 1;
 }
 
 /* ---------------------------------------------------------------------- */
 
 FixRigidSmall::~FixRigidSmall()
 {
   // unregister callbacks to this fix from Atom class
 
   atom->delete_callback(id,0);
 
   // delete locally stored arrays
 
   memory->sfree(body);
   
   memory->destroy(bodyown);
   memory->destroy(bodytag);
   memory->destroy(atom2body);
   memory->destroy(displace);
   memory->destroy(eflags);
   memory->destroy(orient);
   memory->destroy(dorient);
 
   delete random;
   memory->destroy(langextra);
 }
 
 /* ---------------------------------------------------------------------- */
 
 int FixRigidSmall::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 FixRigidSmall::init()
 {
   int i,ibody;
 
   triclinic = domain->triclinic;
 
   // 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 via local comm
    extended flags, mass, COM, inertia tensor, displacement of each atom
    require communication stencil have been setup by comm->borders()
 ------------------------------------------------------------------------- */
 
 void FixRigidSmall::setup_pre_neighbor()
 {
   if (firstflag) {
     firstflag = 0;
     setup_bodies();
-  }
+  } else pre_neighbor();
 }
 
 /* ---------------------------------------------------------------------- */
 
 void FixRigidSmall::setup(int vflag)
 {
   int i,n,ibody;
   double massone,radone;
 
   //check(1);
 
   // sum vcm, fcm, angmom, torque across all rigid bodies
   // vcm = velocity of COM
   // fcm = force on COM
   // angmom = angular momentum around COM
   // torque = torque around COM
 
   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 *image = atom->image;
   int nlocal = atom->nlocal;
 
   double *xcm,*vcm,*fcm,*acm,*tcm;
   double dx,dy,dz;
   double unwrap[3];
 
   for (ibody = 0; ibody < nlocal_body+nghost_body; ibody++) {
     vcm = body[ibody].vcm;
     vcm[0] = vcm[1] = vcm[2] = 0.0;
     fcm = body[ibody].fcm;
     fcm[0] = fcm[1] = fcm[2] = 0.0;
     acm = body[ibody].angmom;
     acm[0] = acm[1] = acm[2] = 0.0;
     tcm = body[ibody].torque;
     tcm[0] = tcm[1] = tcm[2] = 0.0;
   }
 
   for (i = 0; i < nlocal; i++) {
     if (atom2body[i] < 0) continue;
     Body *b = &body[atom2body[i]];
 
     if (rmass) massone = rmass[i];
     else massone = mass[type[i]];
 
     vcm = b->vcm;
     vcm[0] += v[i][0] * massone;
     vcm[1] += v[i][1] * massone;
     vcm[2] += v[i][2] * massone;
     fcm = b->fcm;
     fcm[0] += f[i][0];
     fcm[1] += f[i][1];
     fcm[2] += f[i][2];
 
     domain->unmap(x[i],image[i],unwrap);
     xcm = b->xcm;
     dx = unwrap[0] - xcm[0];
     dy = unwrap[1] - xcm[1];
     dz = unwrap[2] - xcm[2];
 
     acm = b->angmom;
     acm[0] += dy * massone*v[i][2] - dz * massone*v[i][1];
     acm[1] += dz * massone*v[i][0] - dx * massone*v[i][2];
     acm[2] += dx * massone*v[i][1] - dy * massone*v[i][0];
     tcm = b->torque;
     tcm[0] += dy * f[i][2] - dz * f[i][1];
     tcm[1] += dz * f[i][0] - dx * f[i][2];
     tcm[2] += dx * f[i][1] - dy * f[i][0];
   }
 
   // extended particles add their rotation/torque to angmom/torque of body
 
   if (extended) {
     AtomVecLine::Bonus *lbonus;
     if (avec_line) lbonus = avec_line->bonus;
     double **omega = atom->omega;
     double **angmom = atom->angmom;
     double **torque = atom->torque;
     double *radius = atom->radius;
     int *line = atom->line;
 
     for (i = 0; i < nlocal; i++) {
       if (atom2body[i] < 0) continue;
       Body *b = &body[atom2body[i]];
 
       if (eflags[i] & OMEGA) {
         if (eflags[i] & SPHERE) {
           radone = radius[i];
           acm = b->angmom;
           acm[0] += SINERTIA*rmass[i] * radone*radone * omega[i][0];
           acm[1] += SINERTIA*rmass[i] * radone*radone * omega[i][1];
           acm[2] += SINERTIA*rmass[i] * radone*radone * omega[i][2];
         } else if (eflags[i] & LINE) {
           radone = lbonus[line[i]].length;
           b->angmom[2] += LINERTIA*rmass[i] * radone*radone * omega[i][2];
         }
       }
       if (eflags[i] & ANGMOM) {
         acm = b->angmom;
         acm[0] += angmom[i][0];
         acm[1] += angmom[i][1];
         acm[2] += angmom[i][2];
       }
       if (eflags[i] & TORQUE) {
         tcm = b->torque;
         tcm[0] += torque[i][0];
         tcm[1] += torque[i][1];
         tcm[2] += torque[i][2];
       }
     }
   }
 
   // reverse communicate vcm, fcm, angmom, torque of all bodies
 
   commflag = VCM_ANGMOM;
   comm->reverse_comm_variable_fix(this);
   commflag = FORCE_TORQUE;
   comm->reverse_comm_variable_fix(this);
 
   // normalize velocity of COM
 
   for (ibody = 0; ibody < nlocal_body; ibody++) {
     vcm = body[ibody].vcm;
     vcm[0] /= body[ibody].mass;
     vcm[1] /= body[ibody].mass;
     vcm[2] /= body[ibody].mass;
   }
 
   // virial setup before call to set_v
 
   if (vflag) v_setup(vflag);
   else evflag = 0;
 
   // compute and forward communicate updated info of all bodies
 
   for (ibody = 0; ibody < nlocal_body; ibody++) {
     Body *b = &body[ibody];
     MathExtra::angmom_to_omega(b->angmom,b->ex_space,b->ey_space,
                                b->ez_space,b->inertia,b->omega);
   }
 
   commflag = FINAL;
   comm->forward_comm_variable_fix(this);
 
   // set velocity/rotation of atoms in rigid bodues
 
   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 FixRigidSmall::initial_integrate(int vflag)
 {
   double dtfm;
 
   //check(2);
 
   for (int ibody = 0; ibody < nlocal_body; ibody++) {
     Body *b = &body[ibody];
 
     // update vcm by 1/2 step
 
     dtfm = dtf / b->mass;
     b->vcm[0] += dtfm * b->fcm[0];
     b->vcm[1] += dtfm * b->fcm[1];
     b->vcm[2] += dtfm * b->fcm[2];
 
     // update xcm by full step
 
     b->xcm[0] += dtv * b->vcm[0];
     b->xcm[1] += dtv * b->vcm[1];
     b->xcm[2] += dtv * b->vcm[2];
 
     // update angular momentum by 1/2 step
 
     b->angmom[0] += dtf * b->torque[0];
     b->angmom[1] += dtf * b->torque[1];
     b->angmom[2] += dtf * b->torque[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(b->angmom,b->ex_space,b->ey_space,
                                b->ez_space,b->inertia,b->omega);
     MathExtra::richardson(b->quat,b->angmom,b->omega,b->inertia,dtq);
     MathExtra::q_to_exyz(b->quat,b->ex_space,b->ey_space,b->ez_space);
   }
 
   // virial setup before call to set_xv
 
   if (vflag) v_setup(vflag);
   else evflag = 0;
 
   // forward communicate updated info of all bodies
 
   commflag = INITIAL;
   comm->forward_comm_variable_fix(this);
 
   // set coords/orient and velocity/rotation of atoms in rigid bodies
 
   set_xv();
 }
 
 /* ----------------------------------------------------------------------
    apply Langevin thermostat to all 6 DOF of rigid bodies I own
    unlike fix langevin, this stores extra force in extra arrays,
      which are added in when final_integrate() calculates a new fcm/torque
 ------------------------------------------------------------------------- */
 
 void FixRigidSmall::post_force(int vflag)
 {
   double gamma1,gamma2;
 
   // grow langextra if needed
 
   if (nlocal_body > maxlang) {
     memory->destroy(langextra);
     maxlang = nlocal_body + nghost_body;
     memory->create(langextra,maxlang,6,"rigid/small:langextra");
   }
 
   double delta = update->ntimestep - update->beginstep;
   delta /= update->endstep - update->beginstep;
   double 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;
 
   double *vcm,*omega,*inertia;
 
   for (int ibody = 0; ibody < nlocal_body; ibody++) {
     vcm = body[ibody].vcm;
     omega = body[ibody].omega;
     inertia = body[ibody].inertia;
 
     gamma1 = -body[ibody].mass / t_period / ftm2v;
     gamma2 = sqrt(body[ibody].mass) * tsqrt *
       sqrt(24.0*boltz/t_period/dt/mvv2e) / ftm2v;
     langextra[ibody][0] = gamma1*vcm[0] + gamma2*(random->uniform()-0.5);
     langextra[ibody][1] = gamma1*vcm[1] + gamma2*(random->uniform()-0.5);
     langextra[ibody][2] = gamma1*vcm[2] + gamma2*(random->uniform()-0.5);
     
     gamma1 = -1.0 / t_period / ftm2v;
     gamma2 = tsqrt * sqrt(24.0*boltz/t_period/dt/mvv2e) / ftm2v;
     langextra[ibody][3] = inertia[0]*gamma1*omega[0] +
       sqrt(inertia[0])*gamma2*(random->uniform()-0.5);
     langextra[ibody][4] = inertia[1]*gamma1*omega[1] +
       sqrt(inertia[1])*gamma2*(random->uniform()-0.5);
     langextra[ibody][5] = inertia[2]*gamma1*omega[2] +
       sqrt(inertia[2])*gamma2*(random->uniform()-0.5);
   }
 }
 
 /* ---------------------------------------------------------------------- */
 
 void FixRigidSmall::final_integrate()
 {
   int i,ibody;
   double dtfm,xy,xz,yz;
 
   //check(3);
 
   // 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];
   double *xcm,*fcm,*tcm;
 
   for (ibody = 0; ibody < nlocal_body+nghost_body; ibody++) {
     fcm = body[ibody].fcm;
     fcm[0] = fcm[1] = fcm[2] = 0.0;
     tcm = body[ibody].torque;
     tcm[0] = tcm[1] = tcm[2] = 0.0;
   }
 
   for (i = 0; i < nlocal; i++) {
     if (atom2body[i] < 0) continue;
     Body *b = &body[atom2body[i]];
 
     fcm = b->fcm;
     fcm[0] += f[i][0];
     fcm[1] += f[i][1];
     fcm[2] += f[i][2];
 
     domain->unmap(x[i],image[i],unwrap);
     xcm = b->xcm;
     dx = unwrap[0] - xcm[0];
     dy = unwrap[1] - xcm[1];
     dz = unwrap[2] - xcm[2];
 
     tcm = b->torque;
     tcm[0] += dy*f[i][2] - dz*f[i][1];
     tcm[1] += dz*f[i][0] - dx*f[i][2];
     tcm[2] += dx*f[i][1] - dy*f[i][0];
   }
 
   // extended particles add their torque to torque of body
 
   if (extended) {
     double **torque = atom->torque;
 
     for (i = 0; i < nlocal; i++) {
       if (atom2body[i] < 0) continue;
 
       if (eflags[i] & TORQUE) {
         tcm = body[atom2body[i]].torque;
         tcm[0] += torque[i][0];
         tcm[1] += torque[i][1];
         tcm[2] += torque[i][2];
       }
     }
   }
 
   // reverse communicate fcm, torque of all bodies
 
   commflag = FORCE_TORQUE;
   comm->reverse_comm_variable_fix(this);
 
   // include Langevin thermostat forces and torques
 
   if (langflag) {
     for (int ibody = 0; ibody < nlocal_body; ibody++) {
       fcm = body[ibody].fcm;
       fcm[0] += langextra[ibody][0];
       fcm[1] += langextra[ibody][1];
       fcm[2] += langextra[ibody][2];
       tcm = body[ibody].torque;
       tcm[0] += langextra[ibody][3];
       tcm[1] += langextra[ibody][4];
       tcm[2] += langextra[ibody][5];
     }
   }
 
   // update vcm and angmom, recompute omega
   
   for (int ibody = 0; ibody < nlocal_body; ibody++) {
     Body *b = &body[ibody];
 
     // update vcm by 1/2 step
 
     dtfm = dtf / b->mass;
     b->vcm[0] += dtfm * b->fcm[0];
     b->vcm[1] += dtfm * b->fcm[1];
     b->vcm[2] += dtfm * b->fcm[2];
 
     // update angular momentum by 1/2 step
 
     b->angmom[0] += dtf * b->torque[0];
     b->angmom[1] += dtf * b->torque[1];
     b->angmom[2] += dtf * b->torque[2];
 
     MathExtra::angmom_to_omega(b->angmom,b->ex_space,b->ey_space,
                                b->ez_space,b->inertia,b->omega);
   }
 
   // forward communicate updated info of all bodies
 
   commflag = FINAL;
   comm->forward_comm_variable_fix(this);
 
   // set velocity/rotation of atoms in rigid bodies
   // virial is already setup from initial_integrate
 
   set_v();
 }
 
 /* ---------------------------------------------------------------------- */
 
 void FixRigidSmall::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 FixRigidSmall::final_integrate_respa(int ilevel, int iloop)
 {
   dtf = 0.5 * step_respa[ilevel] * force->ftm2v;
   final_integrate();
 }
 
 /* ----------------------------------------------------------------------
    atom to processor assignments have changed,
      so acquire ghost bodies and setup atom2body
    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 FixRigidSmall::pre_neighbor()
 {
   // remap xcm and image flags of each body as needed
 
   tagint original,oldimage,newimage;
 
   for (int ibody = 0; ibody < nlocal_body; ibody++) {
     Body *b = &body[ibody];
 
     original = b->image;
     domain->remap(b->xcm,b->image);
 
     if (original == b->image) b->remapflag[3] = 0;
     else {
       oldimage = original & IMGMASK;
       newimage = b->image & IMGMASK;
       b->remapflag[0] = newimage - oldimage;
       oldimage = (original >> IMGBITS) & IMGMASK;
       newimage = (b->image >> IMGBITS) & IMGMASK;
       b->remapflag[1] = newimage - oldimage;
       oldimage = original >> IMG2BITS;
       newimage = b->image >> IMG2BITS;
       b->remapflag[2] = newimage - oldimage;
       b->remapflag[3] = 1;
     }
   }
 
   // acquire ghost bodies via forward comm
   // also gets new remapflags needed for adjusting atom image flags
   // reset atom2body for owned atoms
   // forward comm sets atom2body for ghost atoms
 
   nghost_body = 0;
   commflag = FULL_BODY;
   comm->forward_comm_variable_fix(this);
   reset_atom2body();
   //check(4);
 
   // adjust image flags of any atom in a rigid body whose xcm was remapped
 
   tagint *image = atom->image;
   int nlocal = atom->nlocal;
 
   int ibody;
   tagint idim,otherdims;
 
   for (int i = 0; i < nlocal; i++) {
     if (atom2body[i] < 0) continue;
     Body *b = &body[atom2body[i]];
 
     if (b->remapflag[3] == 0) continue;
 
     if (b->remapflag[0]) {
       idim = image[i] & IMGMASK;
       otherdims = image[i] ^ idim;
       idim -= b->remapflag[0];
       idim &= IMGMASK;
       image[i] = otherdims | idim;
     }
     if (b->remapflag[1]) {
       idim = (image[i] >> IMGBITS) & IMGMASK;
       otherdims = image[i] ^ (idim << IMGBITS);
       idim -= b->remapflag[1];
       idim &= IMGMASK;
       image[i] = otherdims | (idim << IMGBITS);
     }
     if (b->remapflag[2]) {
       idim = image[i] >> IMG2BITS;
       otherdims = image[i] ^ (idim << IMG2BITS);
       idim -= b->remapflag[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 FixRigidSmall::dof(int tgroup)
 {
   int i,j;
 
   // cannot count DOF correctly unless setup_bodies() 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];
 
   // counts = 3 values per rigid body I own
   // 0 = # of point particles in rigid body and in temperature group
   // 1 = # of finite-size particles in rigid body and in temperature group
   // 2 = # of particles in rigid body, disregarding temperature group
 
   memory->create(counts,nlocal_body+nghost_body,3,"rigid/small:counts");
   for (int i = 0; i < nlocal_body+nghost_body; i++)
     counts[i][0] = counts[i][1] = counts[i][2] = 0;
 
   // tally counts from my owned atoms
   // 0 = # of point particles in rigid body and in temperature group
   // 1 = # of finite-size particles in rigid body and in temperature group
   // 2 = # of particles in rigid body, disregarding temperature group
 
   int *mask = atom->mask;
   int nlocal = atom->nlocal;
 
   for (i = 0; i < nlocal; i++) {
     if (atom2body[i] < 0) continue;
     j = atom2body[i];
     counts[j][2]++;
     if (mask[i] & tgroupbit) {
       if (extended && eflags[i]) counts[j][1]++;
       else counts[j][0]++;
     }
   }
 
   commflag = DOF;
   comm->reverse_comm_variable_fix(this);
 
   // nall = count0 = # of point particles in each rigid body
   // mall = count1 = # of finite-size particles in each rigid body
   // warn if nall+mall != nrigid for any body included in temperature group
 
   int flag = 0;
   for (int ibody = 0; ibody < nlocal_body; ibody++) {
     if (counts[ibody][0]+counts[ibody][1] > 0 &&
         counts[ibody][0]+counts[ibody][1] != counts[ibody][2]) flag = 1;
   }
   int flagall;
   MPI_Allreduce(&flag,&flagall,1,MPI_INT,MPI_MAX,world);
   if (flagall && 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
 
   double *inertia;
 
   int n = 0;
   if (domain->dimension == 3) {
     for (int ibody = 0; ibody < nlocal_body; ibody++) {
       if (counts[ibody][0]+counts[ibody][1] == counts[ibody][2]) {
         n += 3*counts[ibody][0] + 6*counts[ibody][1] - 6;
         inertia = body[ibody].inertia;
         if (inertia[0] == 0.0 || inertia[1] == 0.0 || inertia[2] == 0.0) n++;
       }
     }
   } else if (domain->dimension == 2) {
     for (int ibody = 0; ibody < nlocal_body; ibody++)
       if (counts[ibody][0]+counts[ibody][1] == counts[ibody][2])
         n += 2*counts[ibody][0] + 3*counts[ibody][1] - 3;
   }
 
   memory->destroy(counts);
 
   int nall;
   MPI_Allreduce(&n,&nall,1,MPI_INT,MPI_SUM,world);
   return nall;
 }
 
 /* ----------------------------------------------------------------------
    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 FixRigidSmall::deform(int flag)
 {
   if (flag == 0)
     for (int ibody = 0; ibody < nlocal_body; ibody++)
       domain->x2lamda(body[ibody].xcm,body[ibody].xcm);
   else
     for (int ibody = 0; ibody < nlocal_body; ibody++)
       domain->lamda2x(body[ibody].xcm,body[ibody].xcm);
 }
 
 /* ----------------------------------------------------------------------
    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 FixRigidSmall::set_xv()
 {
   int ibody,itype;
   int xbox,ybox,zbox;
   double x0,x1,x2,v0,v1,v2,fc0,fc1,fc2,massone;
   double ione[3],exone[3],eyone[3],ezone[3],vr[6],p[3][3];
 
   double xprd = domain->xprd;
   double yprd = domain->yprd;
   double zprd = domain->zprd;
   double xy = domain->xy;
   double xz = domain->xz;
   double yz = domain->yz;
 
   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;
 
   // set x and v of each atom
 
   for (int i = 0; i < nlocal; i++) {
     if (atom2body[i] < 0) continue;
     Body *b = &body[atom2body[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(b->ex_space,b->ey_space,b->ez_space,displace[i],x[i]);
 
     v[i][0] = b->omega[1]*x[i][2] - b->omega[2]*x[i][1] + b->vcm[0];
     v[i][1] = b->omega[2]*x[i][0] - b->omega[0]*x[i][2] + b->vcm[1];
     v[i][2] = b->omega[0]*x[i][1] - b->omega[1]*x[i][0] + b->vcm[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] += b->xcm[0] - xbox*xprd;
       x[i][1] += b->xcm[1] - ybox*yprd;
       x[i][2] += b->xcm[2] - zbox*zprd;
     } else {
       x[i][0] += b->xcm[0] - xbox*xprd - ybox*xy - zbox*xz;
       x[i][1] += b->xcm[1] - ybox*yprd - zbox*yz;
       x[i][2] += b->xcm[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 = atom->omega;
     double **angmom = 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 (atom2body[i] < 0) continue;
       Body *b = &body[atom2body[i]];
 
       if (eflags[i] & SPHERE) {
         omega[i][0] = b->omega[0];
         omega[i][1] = b->omega[1];
         omega[i][2] = b->omega[2];
       } else if (eflags[i] & ELLIPSOID) {
         shape = ebonus[ellipsoid[i]].shape;
         quatatom = ebonus[ellipsoid[i]].quat;
         MathExtra::quatquat(b->quat,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(b->omega,exone,eyone,ezone,ione,angmom[i]);
       } else if (eflags[i] & LINE) {
         if (b->quat[3] >= 0.0) theta_body = 2.0*acos(b->quat[0]);
         else theta_body = -2.0*acos(b->quat[0]);
         theta = orient[i][0] + theta_body;
         while (theta <= MINUSPI) theta += TWOPI;
         while (theta > MY_PI) theta -= TWOPI;
         lbonus[line[i]].theta = theta;
         omega[i][0] = b->omega[0];
         omega[i][1] = b->omega[1];
         omega[i][2] = b->omega[2];
       } else if (eflags[i] & TRIANGLE) {
         inertiaatom = tbonus[tri[i]].inertia;
         quatatom = tbonus[tri[i]].quat;
         MathExtra::quatquat(b->quat,orient[i],quatatom);
         MathExtra::qnormalize(quatatom);
         MathExtra::q_to_exyz(quatatom,exone,eyone,ezone);
         MathExtra::omega_to_angmom(b->omega,exone,eyone,ezone,
                                    inertiaatom,angmom[i]);
       }
       if (eflags[i] & DIPOLE) {
         MathExtra::quat_to_mat(b->quat,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 FixRigidSmall::set_v()
 {
   int ibody,itype;
   int xbox,ybox,zbox;
   double dx,dy,dz;
   double x0,x1,x2,v0,v1,v2,fc0,fc1,fc2,massone;
   double ione[3],exone[3],eyone[3],ezone[3],delta[3],vr[6];
 
   double xprd = domain->xprd;
   double yprd = domain->yprd;
   double zprd = domain->zprd;
   double xy = domain->xy;
   double xz = domain->xz;
   double yz = domain->yz;
 
   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;
 
   // set v of each atom
 
   for (int i = 0; i < nlocal; i++) {
     if (atom2body[i] < 0) continue;
     Body *b = &body[atom2body[i]];
 
     MathExtra::matvec(b->ex_space,b->ey_space,b->ez_space,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] = b->omega[1]*delta[2] - b->omega[2]*delta[1] + b->vcm[0];
     v[i][1] = b->omega[2]*delta[0] - b->omega[0]*delta[2] + b->vcm[1];
     v[i][2] = b->omega[0]*delta[1] - b->omega[1]*delta[0] + b->vcm[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 = atom->omega;
     double **angmom = atom->angmom;
     int *ellipsoid = atom->ellipsoid;
     int *tri = atom->tri;
 
     for (int i = 0; i < nlocal; i++) {
       if (atom2body[i] < 0) continue;
       Body *b = &body[atom2body[i]];
 
       if (eflags[i] & SPHERE) {
         omega[i][0] = b->omega[0];
         omega[i][1] = b->omega[1];
         omega[i][2] = b->omega[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(b->omega,exone,eyone,ezone,ione,
                                    angmom[i]);
       } else if (eflags[i] & LINE) {
         omega[i][0] = b->omega[0];
         omega[i][1] = b->omega[1];
         omega[i][2] = b->omega[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(b->omega,exone,eyone,ezone,
                                    inertiaatom,angmom[i]);
       }
     }
   }
 }
 
 /* ----------------------------------------------------------------------
    one-time identification of which atoms are in which rigid bodies
    set bodytag for all owned atoms
 ------------------------------------------------------------------------- */
 
 void FixRigidSmall::create_bodies()
 {
   int i,m,n;
   double unwrap[3];
 
   // error check on image flags of atoms in rigid bodies
 
   int *image = atom->image;
   int *mask = atom->mask;
   int nlocal = atom->nlocal;
 
   int *periodicity = domain->periodicity;
   int xbox,ybox,zbox;
 
   int flag = 0;
   for (i = 0; i < nlocal; i++) {
     if (!(mask[i] & groupbit)) continue;
     xbox = (image[i] & IMGMASK) - IMGMAX;
     ybox = (image[i] >> IMGBITS & IMGMASK) - IMGMAX;
     zbox = (image[i] >> IMG2BITS) - IMGMAX;
     if ((xbox && !periodicity[0]) || (ybox && !periodicity[1]) ||
         (zbox && !periodicity[2])) flag = 1;
   }
 
   int flagall;
   MPI_Allreduce(&flag,&flagall,1,MPI_INT,MPI_SUM,world);
   if (flagall) error->all(FLERR,"Fix rigid/small atom has non-zero image flag "
                           "in a non-periodic dimension");
 
   // allocate buffer for passing messages around ring of procs
   // percount = max number of values to put in buffer for each of ncount
 
   int ncount = 0;
   for (i = 0; i < nlocal; i++)
     if (mask[i] & groupbit) ncount++;
 
   int percount = 5;
   double *buf;
   memory->create(buf,ncount*percount,"rigid/small:buf");
 
   // create map hash for storing unique molecule IDs of my atoms
   // key = molecule ID
   // value = index into per-body data structure
   // n = # of entries in hash
 
   hash = new std::map<int,int>();
   hash->clear();
 
   // setup hash
   // key = body ID
   // value = index into N-length data structure
   // n = count of unique bodies my atoms are part of
 
   int *molecule = atom->molecule;
 
   n = 0;
   for (i = 0; i < nlocal; i++) {
     if (!(mask[i] & groupbit)) continue;
     if (hash->find(molecule[i]) == hash->end()) {
       hash->insert(std::pair<int,int> (molecule[i],n));
       n++;
     }
   }
 
   // bbox = bounding box of each rigid body my atoms are part of
 
   memory->create(bbox,n,6,"rigid/small:bbox");
 
   for (i = 0; i < n; i++) {
     bbox[i][0] = bbox[i][2] = bbox[i][4] = BIG;
     bbox[i][1] = bbox[i][3] = bbox[i][5] = -BIG;
   }
 
   // pack my atoms into buffer as molecule ID, unwrapped coords
 
   double **x = atom->x;
 
   m = 0;
   for (i = 0; i < nlocal; i++) {
     if (!(mask[i] & groupbit)) continue;
     domain->unmap(x[i],image[i],unwrap);
     buf[m++] = molecule[i];
     buf[m++] = unwrap[0];
     buf[m++] = unwrap[1];
     buf[m++] = unwrap[2];
   }
 
   // pass buffer around ring of procs
   // func = update bbox with atom coords from every proc
   // when done, have full bbox for every rigid body my atoms are part of
 
   frsptr = this;
   comm->ring(m,sizeof(double),buf,1,ring_bbox,NULL);
 
   // ctr = center pt of each rigid body my atoms are part of
 
   memory->create(ctr,n,6,"rigid/small:bbox");
 
   for (i = 0; i < n; i++) {
     ctr[i][0] = 0.5 * (bbox[i][0] + bbox[i][1]);
     ctr[i][1] = 0.5 * (bbox[i][2] + bbox[i][3]);
     ctr[i][2] = 0.5 * (bbox[i][4] + bbox[i][5]);
   }
 
   // idclose = ID of atom in body closest to center pt (smaller ID if tied)
   // rsqclose = distance squared from idclose to center pt
 
   memory->create(idclose,n,"rigid/small:idclose");
   memory->create(rsqclose,n,"rigid/small:rsqclose");
 
   for (i = 0; i < n; i++) rsqclose[i] = BIG;
 
   // pack my atoms into buffer as molecule ID, atom ID, unwrapped coords
 
   int *tag = atom->tag;
 
   m = 0;
   for (i = 0; i < nlocal; i++) {
     if (!(mask[i] & groupbit)) continue;
     domain->unmap(x[i],image[i],unwrap);
     buf[m++] = molecule[i];
     buf[m++] = tag[i];
     buf[m++] = unwrap[0];
     buf[m++] = unwrap[1];
     buf[m++] = unwrap[2];
   }
 
   // pass buffer around ring of procs
   // func = update idclose,rsqclose with atom IDs from every proc
   // when done, have idclose for every rigid body my atoms are part of
 
   frsptr = this;
   comm->ring(m,sizeof(double),buf,2,ring_nearest,NULL);
 
   // set bodytag of all owned atoms, based on idclose
   // find max value of rsqclose across all procs
 
   double rsqmax = 0.0;
   for (i = 0; i < nlocal; i++) {
     bodytag[i] = 0;
     if (!(mask[i] & groupbit)) continue;
     m = hash->find(molecule[i])->second;
     bodytag[i] = idclose[m];
     rsqmax = MAX(rsqmax,rsqclose[m]);
   }
 
   // pack my atoms into buffer as bodytag of owning atom, unwrapped coords
 
   m = 0;
   for (i = 0; i < nlocal; i++) {
     if (!(mask[i] & groupbit)) continue;
     domain->unmap(x[i],image[i],unwrap);
     buf[m++] = bodytag[i];
     buf[m++] = unwrap[0];
     buf[m++] = unwrap[1];
     buf[m++] = unwrap[2];
   }
 
   // pass buffer around ring of procs
   // func = update rsqfar for atoms belonging to bodies I own
   // when done, have rsqfar for all atoms in bodies I own
 
   rsqfar = 0.0;
   frsptr = this;
   comm->ring(m,sizeof(double),buf,3,ring_farthest,NULL);
 
   // find maxextent of rsqfar across all procs
 
   MPI_Allreduce(&rsqfar,&maxextent,1,MPI_DOUBLE,MPI_MAX,world);
   maxextent = sqrt(maxextent);
 
   // clean up
 
   delete hash;
   memory->destroy(buf);
   memory->destroy(bbox);
   memory->destroy(ctr);
   memory->destroy(idclose);
   memory->destroy(rsqclose);
 }
 
 /* ----------------------------------------------------------------------
    process rigid body atoms from another proc
    update bounding box for rigid bodies my atoms are part of
 ------------------------------------------------------------------------- */
 
 void FixRigidSmall::ring_bbox(int n, char *cbuf)
 {
   std::map<int,int> *hash = frsptr->hash;
   double **bbox = frsptr->bbox;
 
   double *buf = (double *) cbuf;
   int ndatums = n/4;
 
   int j,imol;
   double *x;
 
   int m = 0;
   for (int i = 0; i < ndatums; i++, m += 4) {
     imol = static_cast<int> (buf[m]);
     if (hash->find(imol) != hash->end()) {
       j = hash->find(imol)->second;
       x = &buf[m+1];
       bbox[j][0] = MIN(bbox[j][0],x[0]);
       bbox[j][1] = MAX(bbox[j][1],x[0]);
       bbox[j][2] = MIN(bbox[j][2],x[1]);
       bbox[j][3] = MAX(bbox[j][3],x[1]);
       bbox[j][4] = MIN(bbox[j][4],x[2]);
       bbox[j][5] = MAX(bbox[j][5],x[2]);
     }
   }
 }
 
 /* ----------------------------------------------------------------------
    process rigid body atoms from another proc
    update nearest atom to body center for rigid bodies my atoms are part of
 ------------------------------------------------------------------------- */
 
 void FixRigidSmall::ring_nearest(int n, char *cbuf)
 {
   std::map<int,int> *hash = frsptr->hash;
   double **ctr = frsptr->ctr;
   int *idclose = frsptr->idclose;
   double *rsqclose = frsptr->rsqclose;
 
   double *buf = (double *) cbuf;
   int ndatums = n/5;
 
   int j,imol,tag;
   double delx,dely,delz,rsq;
   double *x;
 
   int m = 0;
   for (int i = 0; i < ndatums; i++, m += 5) {
     imol = static_cast<int> (buf[m]);
     if (hash->find(imol) != hash->end()) {
       j = hash->find(imol)->second;
       tag = static_cast<int> (buf[m+1]);
       x = &buf[m+2];
       delx = x[0] - ctr[j][0];
       dely = x[1] - ctr[j][1];
       delz = x[2] - ctr[j][2];
       rsq = delx*delx + dely*dely + delz*delz;
       if (rsq <= rsqclose[j]) {
         if (rsq == rsqclose[j] && tag > idclose[j]) continue;
         idclose[j] = tag;
         rsqclose[j] = rsq;
       }
     }
   }
 }
 
 /* ----------------------------------------------------------------------
    process rigid body atoms from another proc
    update rsqfar = distance from owning atom to other atom
 ------------------------------------------------------------------------- */
 
 void FixRigidSmall::ring_farthest(int n, char *cbuf)
 {
   double **x = frsptr->atom->x;
   int *image = frsptr->atom->image;
   int nlocal = frsptr->atom->nlocal;
 
   double *buf = (double *) cbuf;
   int ndatums = n/4;
 
   int itag,iowner;
   double delx,dely,delz,rsq;
   double *xx;
   double unwrap[3];
 
   int m = 0;
   for (int i = 0; i < ndatums; i++, m += 4) {
     itag = static_cast<int> (buf[m]);
     iowner = frsptr->atom->map(itag);
     if (iowner < 0 || iowner >= nlocal) continue;
     frsptr->domain->unmap(x[iowner],image[iowner],unwrap);
     xx = &buf[m+1];
     delx = xx[0] - unwrap[0];
     dely = xx[1] - unwrap[1];
     delz = xx[2] - unwrap[2];
     rsq = delx*delx + dely*dely + delz*delz;
     frsptr->rsqfar = MAX(frsptr->rsqfar,rsq);
   }
 }
 
 /* ----------------------------------------------------------------------
    one-time initialization of rigid body attributes
    extended flags, mass, center-of-mass
    Cartesian and diagonalized inertia tensor
 ------------------------------------------------------------------------- */
 
 void FixRigidSmall::setup_bodies()
 {
   int i,itype,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 (atom2body[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 (atom2body[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;
     }
   }
 
   // acquire ghost bodies via forward comm
   // set atom2body for ghost atoms via forward comm
   // set atom2body for other owned atoms via reset_atom2body()
 
   nghost_body = 0;
   commflag = FULL_BODY;
   comm->forward_comm_variable_fix(this);
   reset_atom2body();
 
   // compute mass & center-of-mass of each rigid body
 
   double **x = atom->x;
   tagint *image = atom->image;
 
   double *xcm;
 
   for (ibody = 0; ibody < nlocal_body+nghost_body; ibody++) {
     xcm = body[ibody].xcm;
     xcm[0] = xcm[1] = xcm[2] = 0.0;
     body[ibody].mass = 0.0;
   }
 
   double unwrap[3];
   double massone;
 
   for (i = 0; i < nlocal; i++) {
     if (atom2body[i] < 0) continue;
     Body *b = &body[atom2body[i]];
 
     if (rmass) massone = rmass[i];
     else massone = mass[type[i]];
 
     domain->unmap(x[i],image[i],unwrap);
     xcm = b->xcm;
     xcm[0] += unwrap[0] * massone;
     xcm[1] += unwrap[1] * massone;
     xcm[2] += unwrap[2] * massone;
     b->mass += massone;
   }
 
   // reverse communicate xcm, mass of all bodies
 
   commflag = XCM_MASS;
   comm->reverse_comm_variable_fix(this);
 
   for (ibody = 0; ibody < nlocal_body; ibody++) {
     xcm = body[ibody].xcm;
     xcm[0] /= body[ibody].mass;
     xcm[1] /= body[ibody].mass;
     xcm[2] /= body[ibody].mass;
   }
 
   // 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 < nlocal_body; ibody++)
     body[ibody].image = ((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
 
   memory->create(itensor,nlocal_body+nghost_body,6,"rigid/small:itensor");
   for (ibody = 0; ibody < nlocal_body+nghost_body; ibody++)
     for (i = 0; i < 6; i++) itensor[ibody][i] = 0.0;
 
   double dx,dy,dz,rad;
   double *inertia;
 
   for (i = 0; i < nlocal; i++) {
     if (atom2body[i] < 0) continue;
     Body *b = &body[atom2body[i]];
 
     domain->unmap(x[i],image[i],unwrap);
     xcm = b->xcm;
     dx = unwrap[0] - xcm[0];
     dy = unwrap[1] - xcm[1];
     dz = unwrap[2] - xcm[2];
 
     if (rmass) massone = rmass[i];
     else massone = mass[type[i]];
 
     inertia = itensor[atom2body[i]];
     inertia[0] += massone * (dy*dy + dz*dz);
     inertia[1] += massone * (dx*dx + dz*dz);
     inertia[2] += massone * (dx*dx + dy*dy);
     inertia[3] -= massone * dy*dz;
     inertia[4] -= massone * dx*dz;
     inertia[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 (atom2body[i] < 0) continue;
       inertia = itensor[atom2body[i]];
 
       if (rmass) massone = rmass[i];
       else massone = mass[type[i]];
 
       if (eflags[i] & SPHERE) {
         inertia[0] += SINERTIA*massone * radius[i]*radius[i];
         inertia[1] += SINERTIA*massone * radius[i]*radius[i];
         inertia[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);
         inertia[0] += ivec[0];
         inertia[1] += ivec[1];
         inertia[2] += ivec[2];
         inertia[3] += ivec[3];
         inertia[4] += ivec[4];
         inertia[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);
         inertia[0] += ivec[0];
         inertia[1] += ivec[1];
         inertia[2] += ivec[2];
         inertia[3] += ivec[3];
         inertia[4] += ivec[4];
         inertia[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);
         inertia[0] += ivec[0];
         inertia[1] += ivec[1];
         inertia[2] += ivec[2];
         inertia[3] += ivec[3];
         inertia[4] += ivec[4];
         inertia[5] += ivec[5];
       }
     }
   }
 
   // reverse communicate inertia tensor of all bodies
 
   commflag = ITENSOR;
   comm->reverse_comm_variable_fix(this);
 
   // 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];
   double *ex,*ey,*ez;
 
   for (ibody = 0; ibody < nlocal_body; ibody++) {
     tensor[0][0] = itensor[ibody][0];
     tensor[1][1] = itensor[ibody][1];
     tensor[2][2] = itensor[ibody][2];
     tensor[1][2] = tensor[2][1] = itensor[ibody][3];
     tensor[0][2] = tensor[2][0] = itensor[ibody][4];
     tensor[0][1] = tensor[1][0] = itensor[ibody][5];
 
     inertia = body[ibody].inertia;
     ierror = MathExtra::jacobi(tensor,inertia,evectors);
     if (ierror) error->all(FLERR,
                            "Insufficient Jacobi rotations for rigid body");
 
     ex = body[ibody].ex_space;
     ex[0] = evectors[0][0];
     ex[1] = evectors[1][0];
     ex[2] = evectors[2][0];
     ey = body[ibody].ey_space;
     ey[0] = evectors[0][1];
     ey[1] = evectors[1][1];
     ey[2] = evectors[2][1];
     ez = body[ibody].ez_space;
     ez[0] = evectors[0][2];
     ez[1] = evectors[1][2];
     ez[2] = evectors[2][2];
 
     // if any principal moment < scaled EPSILON, set to 0.0
 
     double max;
     max = MAX(inertia[0],inertia[1]);
     max = MAX(max,inertia[2]);
 
     if (inertia[0] < EPSILON*max) inertia[0] = 0.0;
     if (inertia[1] < EPSILON*max) inertia[1] = 0.0;
     if (inertia[2] < EPSILON*max) inertia[2] = 0.0;
 
     // enforce 3 evectors as a right-handed coordinate system
     // flip 3rd vector if needed
 
     MathExtra::cross3(ex,ey,cross);
     if (MathExtra::dot3(cross,ez) < 0.0) MathExtra::negate3(ez);
 
     // create initial quaternion
 
     MathExtra::exyz_to_q(ex,ey,ez,body[ibody].quat);
   }
 
   // forward communicate updated info of all bodies
 
   commflag = INITIAL;
   comm->forward_comm_variable_fix(this);
 
   // 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 (atom2body[i] < 0) {
       displace[i][0] = displace[i][1] = displace[i][2] = 0.0;
       continue;
     }
 
     Body *b = &body[atom2body[i]];
 
     domain->unmap(x[i],image[i],unwrap);
     xcm = b->xcm;
     delta[0] = unwrap[0] - xcm[0];
     delta[1] = unwrap[1] - xcm[1];
     delta[2] = unwrap[2] - xcm[2];
     MathExtra::transpose_matvec(b->ex_space,b->ey_space,b->ez_space,
                                 delta,displace[i]);
 
     if (extended) {
       if (eflags[i] & ELLIPSOID) {
         quatatom = ebonus[ellipsoid[i]].quat;
         MathExtra::qconjugate(b->quat,qc);
         MathExtra::quatquat(qc,quatatom,orient[i]);
         MathExtra::qnormalize(orient[i]);
       } else if (eflags[i] & LINE) {
         if (b->quat[3] >= 0.0) theta_body = 2.0*acos(b->quat[0]);
         else theta_body = -2.0*acos(b->quat[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(b->quat,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(b->ex_space,b->ey_space,b->ez_space,
                                     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 < nlocal_body+nghost_body; ibody++)
     for (i = 0; i < 6; i++) itensor[ibody][i] = 0.0;
 
   for (i = 0; i < nlocal; i++) {
     if (atom2body[i] < 0) continue;
     inertia = itensor[atom2body[i]];
 
     if (rmass) massone = rmass[i];
     else massone = mass[type[i]];
 
     inertia[0] += massone *
       (displace[i][1]*displace[i][1] + displace[i][2]*displace[i][2]);
     inertia[1] += massone *
       (displace[i][0]*displace[i][0] + displace[i][2]*displace[i][2]);
     inertia[2] += massone *
       (displace[i][0]*displace[i][0] + displace[i][1]*displace[i][1]);
     inertia[3] -= massone * displace[i][1]*displace[i][2];
     inertia[4] -= massone * displace[i][0]*displace[i][2];
     inertia[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 (atom2body[i] < 0) continue;
       inertia = itensor[atom2body[i]];
 
       if (rmass) massone = rmass[i];
       else massone = mass[type[i]];
 
       if (eflags[i] & SPHERE) {
         inertia[0] += SINERTIA*massone * radius[i]*radius[i];
         inertia[1] += SINERTIA*massone * radius[i]*radius[i];
         inertia[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);
         inertia[0] += ivec[0];
         inertia[1] += ivec[1];
         inertia[2] += ivec[2];
         inertia[3] += ivec[3];
         inertia[4] += ivec[4];
         inertia[5] += ivec[5];
       } else if (eflags[i] & LINE) {
         length = lbonus[line[i]].length;
         MathExtra::inertia_line(length,orient[i][0],massone,ivec);
         inertia[0] += ivec[0];
         inertia[1] += ivec[1];
         inertia[2] += ivec[2];
         inertia[3] += ivec[3];
         inertia[4] += ivec[4];
         inertia[5] += ivec[5];
       } else if (eflags[i] & TRIANGLE) {
         inertiaatom = tbonus[tri[i]].inertia;
         MathExtra::inertia_triangle(inertiaatom,orient[i],massone,ivec);
         inertia[0] += ivec[0];
         inertia[1] += ivec[1];
         inertia[2] += ivec[2];
         inertia[3] += ivec[3];
         inertia[4] += ivec[4];
         inertia[5] += ivec[5];
       }
     }
   }
 
   // reverse communicate inertia tensor of all bodies
 
   commflag = ITENSOR;
   comm->reverse_comm_variable_fix(this);
 
   // error check that re-computed momemts of inertia match diagonalized ones
 
   double *inew;
 
   double norm;
   for (ibody = 0; ibody < nlocal_body; ibody++) {
     inertia = body[ibody].inertia;
 
     if (inertia[0] == 0.0) {
       if (fabs(itensor[ibody][0]) > TOLERANCE)
         error->all(FLERR,"Fix rigid: Bad principal moments");
     } else {
       if (fabs((itensor[ibody][0]-inertia[0])/inertia[0]) >
           TOLERANCE) error->all(FLERR,"Fix rigid: Bad principal moments");
     }
     if (inertia[1] == 0.0) {
       if (fabs(itensor[ibody][1]) > TOLERANCE)
         error->all(FLERR,"Fix rigid: Bad principal moments");
     } else {
       if (fabs((itensor[ibody][1]-inertia[1])/inertia[1]) >
           TOLERANCE) error->all(FLERR,"Fix rigid: Bad principal moments");
     }
     if (inertia[2] == 0.0) {
       if (fabs(itensor[ibody][2]) > TOLERANCE)
         error->all(FLERR,"Fix rigid: Bad principal moments");
     } else {
       if (fabs((itensor[ibody][2]-inertia[2])/inertia[2]) >
           TOLERANCE) error->all(FLERR,"Fix rigid: Bad principal moments");
     }
     norm = (inertia[0] + inertia[1] + inertia[2]) / 3.0;
     if (fabs(itensor[ibody][3]/norm) > TOLERANCE ||
         fabs(itensor[ibody][4]/norm) > TOLERANCE ||
         fabs(itensor[ibody][5]/norm) > TOLERANCE)
       error->all(FLERR,"Fix rigid: Bad principal moments");
   }
 
   // clean up
 
   memory->destroy(itensor);
 }
 
 /* ----------------------------------------------------------------------
    allocate local atom-based arrays
 ------------------------------------------------------------------------- */
 
 void FixRigidSmall::grow_arrays(int nmax)
 {
   memory->grow(bodyown,nmax,"rigid/small:bodyown");
   memory->grow(bodytag,nmax,"rigid/small:bodytag");
   memory->grow(atom2body,nmax,"rigid/small:atom2body");
   memory->grow(displace,nmax,3,"rigid/small:displace");
   if (extended) {
     memory->grow(eflags,nmax,"rigid/small:eflags");
     if (orientflag) memory->grow(orient,nmax,orientflag,"rigid/small:orient");
     if (dorientflag) memory->grow(dorient,nmax,3,"rigid/small:dorient");
   }
 }
 
 /* ----------------------------------------------------------------------
    copy values within local atom-based arrays
 ------------------------------------------------------------------------- */
 
 void FixRigidSmall::copy_arrays(int i, int j, int delflag)
 {
   bodytag[j] = bodytag[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];
     }
   }
 
   // if deleting atom J via delflag and J owns a body, then delete it
 
   if (delflag && bodyown[j] >= 0) {
     bodyown[body[nlocal_body-1].ilocal] = bodyown[j];
     memcpy(&body[bodyown[j]],&body[nlocal_body-1],sizeof(Body));
     nlocal_body--;
   }
 
   // if atom I owns a body, reset I's body.ilocal to loc J
   // do NOT do this if self-copy (I=J) since I's body is already deleted
 
   if (bodyown[i] >= 0 && i != j) body[bodyown[i]].ilocal = j;
   bodyown[j] = bodyown[i];
 }
 
 /* ----------------------------------------------------------------------
    initialize one atom's array values, called when atom is created
 ------------------------------------------------------------------------- */
 
 void FixRigidSmall::set_arrays(int i)
 {
   bodyown[i] = -1;
   bodytag[i] = 0;
   atom2body[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 FixRigidSmall::pack_exchange(int i, double *buf)
 {
   buf[0] = bodytag[i];
   buf[1] = displace[i][0];
   buf[2] = displace[i][1];
   buf[3] = displace[i][2];
 
   // extended attribute info
 
   int m = 4;
   if (extended) {
     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];
     }
   }
 
   // atom not in a rigid body
 
   if (!bodytag[i]) return m;
 
   // atom does not own its rigid body
 
   if (bodyown[i] < 0) {
     buf[m++] = 0;
     return m;
   }
 
   // body info for atom that owns a rigid body
 
   buf[m++] = 1;
   memcpy(&buf[m],&body[bodyown[i]],sizeof(Body));
   m += bodysize;
   return m;
 }
 
 /* ----------------------------------------------------------------------
    unpack values in local atom-based arrays from exchange with another proc
 ------------------------------------------------------------------------- */
 
 int FixRigidSmall::unpack_exchange(int nlocal, double *buf)
 {
   bodytag[nlocal] = static_cast<int> (buf[0]);
   displace[nlocal][0] = buf[1];
   displace[nlocal][1] = buf[2];
   displace[nlocal][2] = buf[3];
 
   // extended attribute info
 
   int m = 4;
   if (extended) {
     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++];
     }
   }
 
   // atom not in a rigid body
 
   if (!bodytag[nlocal]) {
     bodyown[nlocal] = -1;
     return m;
   }
 
   // atom does not own its rigid body
 
   bodyown[nlocal] = static_cast<int> (buf[m++]);
   if (bodyown[nlocal] == 0) {
     bodyown[nlocal] = -1;
     return m;
   }
 
   // body info for atom that owns a rigid body
 
   if (nlocal_body == nmax_body) grow_body();
   memcpy(&body[nlocal_body],&buf[m],sizeof(Body));
   m += bodysize;
   body[nlocal_body].ilocal = nlocal;
   bodyown[nlocal] = nlocal_body++;
 
   return m;
 }
 
 /* ----------------------------------------------------------------------
    only pack body info if own or ghost atom owns the body
    for FULL_BODY, send 0/1 flag with every atom
 ------------------------------------------------------------------------- */
 
 int FixRigidSmall::pack_comm(int n, int *list, double *buf,
                              int pbc_flag, int *pbc)
 {
   int i,j;
   double *xcm,*vcm,*quat,*omega,*ex_space,*ey_space,*ez_space;
 
   int nlocal = atom->nlocal;
 
   int m = 0;
 
   if (commflag == INITIAL) {
     for (i = 0; i < n; i++) {
       j = list[i];
       if (bodyown[j] < 0) continue;
       xcm = body[bodyown[j]].xcm;
       buf[m++] = xcm[0];
       buf[m++] = xcm[1];
       buf[m++] = xcm[2];
       vcm = body[bodyown[j]].vcm;
       buf[m++] = vcm[0];
       buf[m++] = vcm[1];
       buf[m++] = vcm[2];
       quat = body[bodyown[j]].quat;
       buf[m++] = quat[0];
       buf[m++] = quat[1];
       buf[m++] = quat[2];
       buf[m++] = quat[3];
       omega = body[bodyown[j]].omega;
       buf[m++] = omega[0];
       buf[m++] = omega[1];
       buf[m++] = omega[2];
       ex_space = body[bodyown[j]].ex_space;
       buf[m++] = ex_space[0];
       buf[m++] = ex_space[1];
       buf[m++] = ex_space[2];
       ey_space = body[bodyown[j]].ey_space;
       buf[m++] = ey_space[0];
       buf[m++] = ey_space[1];
       buf[m++] = ey_space[2];
       ez_space = body[bodyown[j]].ez_space;
       buf[m++] = ez_space[0];
       buf[m++] = ez_space[1];
       buf[m++] = ez_space[2];
     }
 
   } else if (commflag == FINAL) {
     for (i = 0; i < n; i++) {
       j = list[i];
       if (bodyown[j] < 0) continue;
       vcm = body[bodyown[j]].vcm;
       buf[m++] = vcm[0];
       buf[m++] = vcm[1];
       buf[m++] = vcm[2];
       omega = body[bodyown[j]].omega;
       buf[m++] = omega[0];
       buf[m++] = omega[1];
       buf[m++] = omega[2];
     }
 
   } else if (commflag == FULL_BODY) {
     for (i = 0; i < n; i++) {
       j = list[i];
       if (bodyown[j] < 0) buf[m++] = 0;
       else {
         buf[m++] = 1;
         memcpy(&buf[m],&body[bodyown[j]],sizeof(Body));
         m += bodysize;
       }
     }
   }
 
   return m;
 }
 
 /* ----------------------------------------------------------------------
    only ghost atoms are looped over
    for FULL_BODY, store a new ghost body if this atom owns it
    for other commflag values, only unpack body info if atom owns it
 ------------------------------------------------------------------------- */
 
 void FixRigidSmall::unpack_comm(int n, int first, double *buf)
 {
   int i,j,last,flag;
   double *xcm,*vcm,*quat,*omega,*ex_space,*ey_space,*ez_space;
 
   int m = 0;
   last = first + n;
 
   if (commflag == INITIAL) {
     for (i = first; i < last; i++) {
       if (bodyown[i] < 0) continue;
       xcm = body[bodyown[i]].xcm;
       xcm[0] = buf[m++];
       xcm[1] = buf[m++];
       xcm[2] = buf[m++];
       vcm = body[bodyown[i]].vcm;
       vcm[0] = buf[m++];
       vcm[1] = buf[m++];
       vcm[2] = buf[m++];
       quat = body[bodyown[i]].quat;
       quat[0] = buf[m++];
       quat[1] = buf[m++];
       quat[2] = buf[m++];
       quat[3] = buf[m++];
       omega = body[bodyown[i]].omega;
       omega[0] = buf[m++];
       omega[1] = buf[m++];
       omega[2] = buf[m++];
       ex_space = body[bodyown[i]].ex_space;
       ex_space[0] = buf[m++];
       ex_space[1] = buf[m++];
       ex_space[2] = buf[m++];
       ey_space = body[bodyown[i]].ey_space;
       ey_space[0] = buf[m++];
       ey_space[1] = buf[m++];
       ey_space[2] = buf[m++];
       ez_space = body[bodyown[i]].ez_space;
       ez_space[0] = buf[m++];
       ez_space[1] = buf[m++];
       ez_space[2] = buf[m++];
     }
 
   } else if (commflag == FINAL) {
     for (i = first; i < last; i++) {
       if (bodyown[i] < 0) continue;
       vcm = body[bodyown[i]].vcm;
       vcm[0] = buf[m++];
       vcm[1] = buf[m++];
       vcm[2] = buf[m++];
       omega = body[bodyown[i]].omega;
       omega[0] = buf[m++];
       omega[1] = buf[m++];
       omega[2] = buf[m++];
     }
 
   } else if (commflag == FULL_BODY) {
     for (i = first; i < last; i++) {
       bodyown[i] = static_cast<int> (buf[m++]);
       if (bodyown[i] == 0) bodyown[i] = -1;
       else {
         j = nlocal_body + nghost_body;
         if (j == nmax_body) grow_body();
         memcpy(&body[j],&buf[m],sizeof(Body));
         m += bodysize;
         body[j].ilocal = i;
         bodyown[i] = j;
         nghost_body++;
       }
     }
   }
 }
 
 /* ----------------------------------------------------------------------
    only ghost atoms are looped over
    only pack body info if atom owns it
 ------------------------------------------------------------------------- */
 
 int FixRigidSmall::pack_reverse_comm(int n, int first, double *buf)
 {
   int i,j,m,last;
   double *fcm,*torque,*vcm,*angmom,*xcm;
 
   m = 0;
   last = first + n;
 
   if (commflag == FORCE_TORQUE) {
     for (i = first; i < last; i++) {
       if (bodyown[i] < 0) continue;
       fcm = body[bodyown[i]].fcm;
       buf[m++] = fcm[0];
       buf[m++] = fcm[1];
       buf[m++] = fcm[2];
       torque = body[bodyown[i]].torque;
       buf[m++] = torque[0];
       buf[m++] = torque[1];
       buf[m++] = torque[2];
     }
 
   } else if (commflag == VCM_ANGMOM) {
     for (i = first; i < last; i++) {
       if (bodyown[i] < 0) continue;
       vcm = body[bodyown[i]].vcm;
       buf[m++] = vcm[0];
       buf[m++] = vcm[1];
       buf[m++] = vcm[2];
       angmom = body[bodyown[i]].angmom;
       buf[m++] = angmom[0];
       buf[m++] = angmom[1];
       buf[m++] = angmom[2];
     }
 
   } else if (commflag == XCM_MASS) {
     for (i = first; i < last; i++) {
       if (bodyown[i] < 0) continue;
       xcm = body[bodyown[i]].xcm;
       buf[m++] = xcm[0];
       buf[m++] = xcm[1];
       buf[m++] = xcm[2];
       buf[m++] = body[bodyown[i]].mass;
     }
 
   } else if (commflag == ITENSOR) {
     for (i = first; i < last; i++) {
       if (bodyown[i] < 0) continue;
       j = bodyown[i];
       buf[m++] = itensor[j][0];
       buf[m++] = itensor[j][1];
       buf[m++] = itensor[j][2];
       buf[m++] = itensor[j][3];
       buf[m++] = itensor[j][4];
       buf[m++] = itensor[j][5];
     }
 
   } else if (commflag == DOF) {
     for (i = first; i < last; i++) {
       if (bodyown[i] < 0) continue;
       j = bodyown[i];
       buf[m++] = counts[j][0];
       buf[m++] = counts[j][1];
       buf[m++] = counts[j][2];
     }
   }
 
   return m;
 }
 
 /* ----------------------------------------------------------------------
    only unpack body info if own or ghost atom owns the body
 ------------------------------------------------------------------------- */
 
 void FixRigidSmall::unpack_reverse_comm(int n, int *list, double *buf)
 {
   int i,j,k;
   double *fcm,*torque,*vcm,*angmom,*xcm;
 
   int *tag = atom->tag;
   int nlocal = atom->nlocal;
 
   int m = 0;
 
   if (commflag == FORCE_TORQUE) {
     for (i = 0; i < n; i++) {
       j = list[i];
       if (bodyown[j] < 0) continue;
       fcm = body[bodyown[j]].fcm;
       fcm[0] += buf[m++];
       fcm[1] += buf[m++];
       fcm[2] += buf[m++];
       torque = body[bodyown[j]].torque;
       torque[0] += buf[m++];
       torque[1] += buf[m++];
       torque[2] += buf[m++];
     }
 
   } else if (commflag == VCM_ANGMOM) {
     for (i = 0; i < n; i++) {
       j = list[i];
       if (bodyown[j] < 0) continue;
       vcm = body[bodyown[j]].vcm;
       vcm[0] += buf[m++];
       vcm[1] += buf[m++];
       vcm[2] += buf[m++];
       angmom = body[bodyown[j]].angmom;
       angmom[0] += buf[m++];
       angmom[1] += buf[m++];
       angmom[2] += buf[m++];
     }
 
   } else if (commflag == XCM_MASS) {
     for (i = 0; i < n; i++) {
       j = list[i];
       if (bodyown[j] < 0) continue;
       xcm = body[bodyown[j]].xcm;
       xcm[0] += buf[m++];
       xcm[1] += buf[m++];
       xcm[2] += buf[m++];
       body[bodyown[j]].mass += buf[m++];
     }
 
   } else if (commflag == ITENSOR) {
     for (i = 0; i < n; i++) {
       j = list[i];
       if (bodyown[j] < 0) continue;
       k = bodyown[j];
       itensor[k][0] += buf[m++];
       itensor[k][1] += buf[m++];
       itensor[k][2] += buf[m++];
       itensor[k][3] += buf[m++];
       itensor[k][4] += buf[m++];
       itensor[k][5] += buf[m++];
     }
 
   } else if (commflag == DOF) {
     for (i = 0; i < n; i++) {
       j = list[i];
       if (bodyown[j] < 0) continue;
       k = bodyown[j];
       counts[k][0] += buf[m++];
       counts[k][1] += buf[m++];
       counts[k][2] += buf[m++];
     }
   }
 }
 
 /* ----------------------------------------------------------------------
    grow body data structure
 ------------------------------------------------------------------------- */
 
 void FixRigidSmall::grow_body()
 {
   nmax_body += DELTA_BODY;
   body = (Body *) memory->srealloc(body,nmax_body*sizeof(Body),
                                    "rigid/small:body");
 }
 
 /* ----------------------------------------------------------------------
    reset atom2body for all owned atoms
    do this via bodyown of atom that owns the body the owned atom is in
    atom2body values can point to original body or any image of the body
 ------------------------------------------------------------------------- */
 
 void FixRigidSmall::reset_atom2body()
 {
   int iowner;
 
   // iowner = index of atom that owns the body that atom I is in
 
   int nlocal = atom->nlocal;
 
   for (int i = 0; i < nlocal; i++) {
     atom2body[i] = -1;
     if (bodytag[i]) {
       iowner = atom->map(bodytag[i]);
       if (iowner == -1) {
         char str[128];
         sprintf(str,
                 "Rigid body atoms %d %d missing on proc %d at step " 
                 BIGINT_FORMAT,
                 atom->tag[i],bodytag[i],comm->me,update->ntimestep);
         error->one(FLERR,str);
         
       }
       atom2body[i] = bodyown[iowner];
     }
   }
 }
 
 /* ---------------------------------------------------------------------- */
 
 void FixRigidSmall::reset_dt()
 {
   dtv = update->dt;
   dtf = 0.5 * update->dt * force->ftm2v;
   dtq = 0.5 * update->dt;
 }
 
 /* ----------------------------------------------------------------------
    return temperature of collection of rigid bodies
    non-active DOF are removed by fflag/tflag and in tfactor
 ------------------------------------------------------------------------- */
 
 double FixRigidSmall::compute_scalar()
 {
   double wbody[3],rot[3][3];
 
   double *vcm,*inertia;
 
   double t = 0.0;
 
   for (int i = 0; i < nlocal_body; i++) {
     vcm = body[i].vcm;
     t += body[i].mass * (vcm[0]*vcm[0] + vcm[1]*vcm[1] + vcm[2]*vcm[2]);
 
     // for Iw^2 rotational term, need wbody = angular velocity in body frame 
     // not omega = angular velocity in space frame
 
     inertia = body[i].inertia;
     MathExtra::quat_to_mat(body[i].quat,rot);
     MathExtra::transpose_matvec(rot,body[i].angmom,wbody);
     if (inertia[0] == 0.0) wbody[0] = 0.0;
     else wbody[0] /= inertia[0];
     if (inertia[1] == 0.0) wbody[1] = 0.0;
     else wbody[1] /= inertia[1];
     if (inertia[2] == 0.0) wbody[2] = 0.0;
     else wbody[2] /= inertia[2];
 
     t += inertia[0]*wbody[0]*wbody[0] + inertia[1]*wbody[1]*wbody[1] +
       inertia[2]*wbody[2]*wbody[2];
   }
 
   double tall;
   MPI_Allreduce(&t,&tall,1,MPI_DOUBLE,MPI_SUM,world);
 
   double tfactor = force->mvv2e / (6.0*nbody * force->boltz);
   tall *= tfactor;
   return tall;
 }
 
 /* ----------------------------------------------------------------------
    memory usage of local atom-based arrays
 ------------------------------------------------------------------------- */
 
 double FixRigidSmall::memory_usage()
 {
   int nmax = atom->nmax;
   double bytes = 2 * 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);
   }
   bytes += nmax_body * sizeof(Body);
   return bytes;
 }
 
 /* ----------------------------------------------------------------------
    debug method for sanity checking of atom/body data pointers
 ------------------------------------------------------------------------- */
 
 /*
 void FixRigidSmall::check(int flag)
 {
   for (int i = 0; i < atom->nlocal; i++) {
     if (bodyown[i] >= 0) {
       if (bodytag[i] != atom->tag[i]) {
         printf("Proc %d, step %ld, flag %d\n",comm->me,update->ntimestep,flag);
         errorx->one(FLERR,"BAD AAA");
       }
       if (bodyown[i] < 0 || bodyown[i] >= nlocal_body) {
         printf("Proc %d, step %ld, flag %d\n",comm->me,update->ntimestep,flag);
         errorx->one(FLERR,"BAD BBB");
       }
       if (atom2body[i] != bodyown[i]) {
         printf("Proc %d, step %ld, flag %d\n",comm->me,update->ntimestep,flag);
         errorx->one(FLERR,"BAD CCC");
       }
       if (body[bodyown[i]].ilocal != i) {
         printf("Proc %d, step %ld, flag %d\n",comm->me,update->ntimestep,flag);
         errorx->one(FLERR,"BAD DDD");
       }
     }
   }
 
   for (int i = 0; i < atom->nlocal; i++) {
     if (bodyown[i] < 0 && bodytag[i] > 0) {
       if (atom2body[i] < 0 || atom2body[i] >= nlocal_body+nghost_body) {
         printf("Proc %d, step %ld, flag %d\n",comm->me,update->ntimestep,flag);
         errorx->one(FLERR,"BAD EEE");
       }
       if (bodytag[i] != atom->tag[body[atom2body[i]].ilocal]) {
         printf("Proc %d, step %ld, flag %d\n",comm->me,update->ntimestep,flag);
         errorx->one(FLERR,"BAD FFF");
       }
     }
   }
 
   for (int i = atom->nlocal; i < atom->nlocal + atom->nghost; i++) {
     if (bodyown[i] >= 0) {
       if (bodyown[i] < nlocal_body || 
           bodyown[i] >= nlocal_body+nghost_body) {
         printf("Values %d %d: %d %d %d\n",
                i,atom->tag[i],bodyown[i],nlocal_body,nghost_body);
         printf("Proc %d, step %ld, flag %d\n",comm->me,update->ntimestep,flag);
         errorx->one(FLERR,"BAD GGG");
       }
       if (body[bodyown[i]].ilocal != i) {
         printf("Proc %d, step %ld, flag %d\n",comm->me,update->ntimestep,flag);
         errorx->one(FLERR,"BAD HHH");
       }
     }
   }
 
   for (int i = 0; i < nlocal_body; i++) {
     if (body[i].ilocal < 0 || body[i].ilocal >= atom->nlocal) {
       printf("Proc %d, step %ld, flag %d\n",comm->me,update->ntimestep,flag);
       errorx->one(FLERR,"BAD III");
     }
     if (bodytag[body[i].ilocal] != atom->tag[body[i].ilocal] || 
         bodyown[body[i].ilocal] != i) {
       printf("Proc %d, step %ld, flag %d\n",comm->me,update->ntimestep,flag);
       errorx->one(FLERR,"BAD JJJ");
     }
   }
 
   for (int i = nlocal_body; i < nlocal_body + nghost_body; i++) {
     if (body[i].ilocal < atom->nlocal || 
         body[i].ilocal >= atom->nlocal + atom->nghost) {
       printf("Proc %d, step %ld, flag %d\n",comm->me,update->ntimestep,flag);
       errorx->one(FLERR,"BAD KKK");
     }
     if (bodyown[body[i].ilocal] != i) {
       printf("Proc %d, step %ld, flag %d\n",comm->me,update->ntimestep,flag);
       errorx->one(FLERR,"BAD LLL");
     }
   }
 }
 */