git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@6630 f3b2605a-c512-4ea7-a41b-209d697bcdaa

src/USER-MISC/Install.sh

@@ -0,0 +1,19 @@
+# Install/unInstall package files in LAMMPS
+
+if (test $1 = 1) then
+
+  cp compute_temp_rotate.cpp ..
+  cp fix_addtorque.cpp ..
+
+  cp compute_temp_rotate.h ..
+  cp fix_addtorque.h ..
+
+elif (test $1 = 0) then
+
+  rm -f ../compute_temp_rotate.cpp
+  rm -f ../fix_addtorque.cpp
+
+  rm -f ../compute_temp_rotate.h
+  rm -f ../fix_addtorque.h
+
+fi

src/USER-MISC/README

@@ -0,0 +1,20 @@
+The files in this directory are a potpourri of (mostly) unrelated
+features contributed to LAMMPS by users.  Each feature is a single
+file (actually a *.cpp and *.h file).
+
+More information about each feature can be found by reading its doc
+page in the LAMMPS doc directory.  This link points to the doc
+page for all LAMMPS commands:
+
+http://lammps.sandia.gov/doc/Section_commands.html#3_5\
+
+User-contributed features are listed at the bottom of the fix,
+compute, pair, etc sections.
+
+You should contact the author if you have specific questions about the
+feature or its code.
+
+------------------------------------------------------------
+
+compute temp/rotate, Laurent Joly (U Lyon, France), ljoly.ulyon at gmail.com, 8Aug11
+fix addtorque, Laurent Joly (U Lyon, France), ljoly.ulyon at gmail.com, 8Aug11

src/USER-MISC/compute_temp_rotate.cpp

@@ -0,0 +1,294 @@
+/* ----------------------------------------------------------------------
+   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.
+------------------------------------------------------------------------- */
+
+/* ----------------------------------------------------------------------
+   Contributing author: Laurent Joly (U Lyon, France)
+------------------------------------------------------------------------- */
+
+#include "mpi.h"
+#include "stdlib.h"
+#include "string.h"
+#include "compute_temp_rotate.h"
+#include "atom.h"
+#include "update.h"
+#include "force.h"
+#include "group.h"
+#include "modify.h"
+#include "fix.h"
+#include "domain.h"
+#include "lattice.h"
+#include "error.h"
+#include "memory.h"
+
+using namespace LAMMPS_NS;
+
+#define MIN(A,B) ((A) < (B)) ? (A) : (B)
+#define MAX(A,B) ((A) > (B)) ? (A) : (B)
+
+/* ---------------------------------------------------------------------- */
+
+ComputeTempRotate::ComputeTempRotate(LAMMPS *lmp, int narg, char **arg) : 
+  Compute(lmp, narg, arg)
+{
+  if (narg != 3) error->all("Illegal compute temp/rotate command");
+
+  scalar_flag = vector_flag = 1;
+  size_vector = 6;
+  extscalar = 0;
+  extvector = 1;
+  tempflag = 1;
+  tempbias = 1;
+
+  maxbias = 0;
+  vbiasall = NULL;
+  vector = new double[6];
+}
+
+/* ---------------------------------------------------------------------- */
+
+ComputeTempRotate::~ComputeTempRotate()
+{
+  memory->destroy(vbiasall);
+  delete [] vector;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void ComputeTempRotate::init()
+{
+  fix_dof = 0;
+  for (int i = 0; i < modify->nfix; i++)
+    fix_dof += modify->fix[i]->dof(igroup);
+  dof_compute();
+
+  masstotal = group->mass(igroup);
+}
+
+/* ---------------------------------------------------------------------- */
+
+void ComputeTempRotate::dof_compute()
+{
+  double natoms = group->count(igroup);
+  int nper = domain->dimension;
+  dof = nper * natoms;
+  dof -= extra_dof + fix_dof;
+  if (dof > 0) tfactor = force->mvv2e / (dof * force->boltz);
+  else tfactor = 0.0;
+}
+
+/* ---------------------------------------------------------------------- */
+
+double ComputeTempRotate::compute_scalar()
+{
+  double vthermal[3];
+  double vcm[3],xcm[3],inertia[3][3],angmom[3],omega[3];
+  int xbox,ybox,zbox;
+  double dx,dy,dz;
+  double xprd = domain->xprd;
+  double yprd = domain->yprd;
+  double zprd = domain->zprd;
+
+  invoked_scalar = update->ntimestep;
+
+  if (dynamic) masstotal = group->mass(igroup);
+  group->vcm(igroup,masstotal,vcm);
+  group->xcm(igroup,masstotal,xcm);
+  group->inertia(igroup,xcm,inertia);
+  group->angmom(igroup,xcm,angmom);
+  group->omega(angmom,inertia,omega);
+
+  double **x = atom->x;
+  double **v = atom->v;
+  double *mass = atom->mass;
+  double *rmass = atom->rmass;
+  int *type = atom->type;
+  int *image = atom->image;
+  int *mask = atom->mask;
+  int nlocal = atom->nlocal;
+
+  if (nlocal > maxbias) {
+    memory->destroy(vbiasall);
+    maxbias = atom->nmax;
+    memory->create(vbiasall,maxbias,3,"temp/rotate:vbiasall");
+  }
+
+  double t = 0.0;
+  
+  for (int i = 0; i < nlocal; i++)
+    if (mask[i] & groupbit) {
+      
+      xbox = (image[i] & 1023) - 512;
+      ybox = (image[i] >> 10 & 1023) - 512;
+      zbox = (image[i] >> 20) - 512;
+      dx = (x[i][0] + xbox*xprd) - xcm[0];
+      dy = (x[i][1] + ybox*yprd) - xcm[1];
+      dz = (x[i][2] + zbox*zprd) - xcm[2];
+      vbiasall[i][0] = vcm[0] + dz*omega[1]-dy*omega[2];
+      vbiasall[i][1] = vcm[1] + dx*omega[2]-dz*omega[0];
+      vbiasall[i][2] = vcm[2] + dy*omega[0]-dx*omega[1];
+
+      vthermal[0] = v[i][0] - vbiasall[i][0];
+      vthermal[1] = v[i][1] - vbiasall[i][1];
+      vthermal[2] = v[i][2] - vbiasall[i][2];
+      if (rmass)
+	t += (vthermal[0]*vthermal[0] + vthermal[1]*vthermal[1] + 
+	      vthermal[2]*vthermal[2]) * rmass[i];
+      else
+	t += (vthermal[0]*vthermal[0] + vthermal[1]*vthermal[1] + 
+	      vthermal[2]*vthermal[2]) * mass[type[i]];
+    }
+
+  MPI_Allreduce(&t,&scalar,1,MPI_DOUBLE,MPI_SUM,world);
+  if (dynamic) dof_compute();
+  scalar *= tfactor;
+  return scalar;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void ComputeTempRotate::compute_vector()
+{
+  int i;
+  double vthermal[3];
+  double vcm[3],xcm[3],inertia[3][3],angmom[3],omega[3];
+  int xbox,ybox,zbox;
+  double dx,dy,dz;
+  double xprd = domain->xprd;
+  double yprd = domain->yprd;
+  double zprd = domain->zprd;
+
+  invoked_vector = update->ntimestep;
+
+  if (dynamic) masstotal = group->mass(igroup);
+  group->vcm(igroup,masstotal,vcm);
+  group->xcm(igroup,masstotal,xcm);
+  group->inertia(igroup,xcm,inertia);
+  group->angmom(igroup,xcm,angmom);
+  group->omega(angmom,inertia,omega);
+
+  double **x = atom->x;
+  double **v = atom->v;
+  double *mass = atom->mass;
+  double *rmass = atom->rmass;
+  int *type = atom->type;
+  int *image = atom->image;
+  int *mask = atom->mask;
+  int nlocal = atom->nlocal;
+
+  if (nlocal > maxbias) {
+    memory->destroy(vbiasall);
+    maxbias = atom->nmax;
+    memory->create(vbiasall,maxbias,3,"temp/rotate:vbiasall");
+  }
+
+  double massone,t[6];
+  for (i = 0; i < 6; i++) t[i] = 0.0;
+
+  for (i = 0; i < nlocal; i++)
+    if (mask[i] & groupbit) {
+
+      xbox = (image[i] & 1023) - 512;
+      ybox = (image[i] >> 10 & 1023) - 512;
+      zbox = (image[i] >> 20) - 512;
+      dx = (x[i][0] + xbox*xprd) - xcm[0];
+      dy = (x[i][1] + ybox*yprd) - xcm[1];
+      dz = (x[i][2] + zbox*zprd) - xcm[2];
+      vbiasall[i][0] = vcm[0] + dz*omega[1]-dy*omega[2];
+      vbiasall[i][1] = vcm[1] + dx*omega[2]-dz*omega[0];
+      vbiasall[i][2] = vcm[2] + dy*omega[0]-dx*omega[1];
+
+      vthermal[0] = v[i][0] - vbiasall[i][0];
+      vthermal[1] = v[i][1] - vbiasall[i][1];
+      vthermal[2] = v[i][2] - vbiasall[i][2];
+
+      if (rmass) massone = rmass[i];
+      else massone = mass[type[i]];
+      t[0] += massone * vthermal[0]*vthermal[0];
+      t[1] += massone * vthermal[1]*vthermal[1];
+      t[2] += massone * vthermal[2]*vthermal[2];
+      t[3] += massone * vthermal[0]*vthermal[1];
+      t[4] += massone * vthermal[0]*vthermal[2];
+      t[5] += massone * vthermal[1]*vthermal[2];
+    }
+
+  MPI_Allreduce(t,vector,6,MPI_DOUBLE,MPI_SUM,world);
+  for (i = 0; i < 6; i++) vector[i] *= force->mvv2e;
+}
+
+/* ----------------------------------------------------------------------
+   remove velocity bias from atom I to leave thermal velocity
+------------------------------------------------------------------------- */
+
+void ComputeTempRotate::remove_bias(int i, double *v)
+{
+  v[0] -= vbiasall[i][0];
+  v[1] -= vbiasall[i][1];
+  v[2] -= vbiasall[i][2];
+}
+
+/* ----------------------------------------------------------------------
+   remove velocity bias from all atoms to leave thermal velocity
+------------------------------------------------------------------------- */
+
+void ComputeTempRotate::remove_bias_all()
+{
+  double **v = atom->v;
+  int *mask = atom->mask;
+  int nlocal = atom->nlocal;
+  
+  for (int i = 0; i < nlocal; i++)
+    if (mask[i] & groupbit) {   
+      v[i][0] -= vbiasall[i][0];
+      v[i][1] -= vbiasall[i][1];
+      v[i][2] -= vbiasall[i][2];
+    }
+}
+
+/* ----------------------------------------------------------------------
+   add back in velocity bias to atom I removed by remove_bias()
+   assume remove_bias() was previously called
+------------------------------------------------------------------------- */
+
+void ComputeTempRotate::restore_bias(int i, double *v)
+{
+  v[0] += vbiasall[i][0];
+  v[1] += vbiasall[i][1];
+  v[2] += vbiasall[i][2];
+}
+
+/* ----------------------------------------------------------------------
+   add back in velocity bias to all atoms removed by remove_bias_all()
+   assume remove_bias_all() was previously called
+------------------------------------------------------------------------- */
+
+void ComputeTempRotate::restore_bias_all()
+{
+  double **v = atom->v;
+  int *mask = atom->mask;
+  int nlocal = atom->nlocal;
+  
+  for (int i = 0; i < nlocal; i++)
+    if (mask[i] & groupbit) {
+      v[i][0] += vbiasall[i][0];
+      v[i][1] += vbiasall[i][1];
+      v[i][2] += vbiasall[i][2];
+    }
+}
+
+/* ---------------------------------------------------------------------- */
+
+double ComputeTempRotate::memory_usage()
+{
+  double bytes = maxbias * sizeof(double);
+  return bytes;
+}

src/USER-MISC/compute_temp_rotate.h

@@ -0,0 +1,54 @@
+/* ----------------------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   http://lammps.sandia.gov, Sandia National Laboratories
+   Steve Plimpton, sjplimp@sandia.gov
+
+   Copyright (2003) Sandia Corporation.  Under the terms of Contract
+   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
+   certain rights in this software.  This software is distributed under 
+   the GNU General Public License.
+
+   See the README file in the top-level LAMMPS directory.
+------------------------------------------------------------------------- */
+
+#ifdef COMPUTE_CLASS
+
+ComputeStyle(temp/rotate,ComputeTempRotate)
+
+#else
+
+#ifndef LMP_COMPUTE_TEMP_ROTATE_H
+#define LMP_COMPUTE_TEMP_ROTATE_H
+
+#include "compute.h"
+
+namespace LAMMPS_NS {
+
+class ComputeTempRotate : public Compute {
+ public:
+  ComputeTempRotate(class LAMMPS *, int, char **);
+  ~ComputeTempRotate();
+  void init();
+  double compute_scalar();
+  void compute_vector();
+
+  void remove_bias(int, double *);
+  void remove_bias_all();
+  void restore_bias(int, double *);
+  void restore_bias_all();
+  double memory_usage();
+
+ private:
+  int fix_dof;
+  double tfactor,masstotal;
+  double **vbiasall;  // stored velocity bias for all atoms
+  int maxbias;        // size of vbiasall array
+
+  void dof_compute(); //without virtual
+
+};
+
+}
+
+#endif
+#endif

src/USER-MISC/fix_addtorque.cpp

@@ -0,0 +1,292 @@
+/* ----------------------------------------------------------------------
+   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.
+------------------------------------------------------------------------- */
+
+/* ----------------------------------------------------------------------
+   Contributing author: Laurent Joly (U Lyon, France)
+------------------------------------------------------------------------- */
+
+#include "string.h"
+#include "stdlib.h"
+#include "fix_addtorque.h"
+#include "atom.h"
+#include "update.h"
+#include "modify.h"
+#include "domain.h"
+#include "respa.h"
+#include "input.h"
+#include "variable.h"
+#include "memory.h"
+#include "error.h"
+#include "group.h"
+#include "force.h"
+
+using namespace LAMMPS_NS;
+
+enum{NONE,CONSTANT,EQUAL,ATOM};
+
+/* ---------------------------------------------------------------------- */
+
+FixAddTorque::FixAddTorque(LAMMPS *lmp, int narg, char **arg) :
+  Fix(lmp, narg, arg)
+{
+  if (narg != 6) error->all("Illegal fix addtorque command");
+
+  scalar_flag = 1;
+  vector_flag = 1;
+  size_vector = 3;
+  global_freq = 1;
+  extscalar = 1;
+  extvector = 1;
+
+  xstr = ystr = zstr = NULL;
+
+  if (strstr(arg[3],"v_") == arg[3]) {
+    int n = strlen(&arg[3][2]) + 1;
+    xstr = new char[n];
+    strcpy(xstr,&arg[3][2]);
+  } else {
+    xvalue = atof(arg[3]);
+    xstyle = CONSTANT;
+  }
+  if (strstr(arg[4],"v_") == arg[4]) {
+    int n = strlen(&arg[4][2]) + 1;
+    ystr = new char[n];
+    strcpy(ystr,&arg[4][2]);
+  } else {
+    yvalue = atof(arg[4]);
+    ystyle = CONSTANT;
+  }
+  if (strstr(arg[5],"v_") == arg[5]) {
+    int n = strlen(&arg[5][2]) + 1;
+    zstr = new char[n];
+    strcpy(zstr,&arg[5][2]);
+  } else {
+    zvalue = atof(arg[5]);
+    zstyle = CONSTANT;
+  }
+  
+  force_flag = 0;
+  foriginal[0] = foriginal[1] = foriginal[2] = foriginal[3] = 0.0;
+}
+
+/* ---------------------------------------------------------------------- */
+
+FixAddTorque::~FixAddTorque()
+{
+  delete [] xstr;
+  delete [] ystr;
+  delete [] zstr;
+}
+
+/* ---------------------------------------------------------------------- */
+
+int FixAddTorque::setmask()
+{
+  int mask = 0;
+  mask |= POST_FORCE;
+  mask |= THERMO_ENERGY;
+  mask |= POST_FORCE_RESPA;
+  mask |= MIN_POST_FORCE;
+  return mask;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixAddTorque::init()
+{
+  // check variables
+
+  if (xstr) {
+    xvar = input->variable->find(xstr);
+    if (xvar < 0) error->all("Variable name for fix addtorque does not exist");
+    if (input->variable->equalstyle(xvar)) xstyle = EQUAL;
+    else error->all("Variable for fix addtorque is invalid style");
+  }
+  if (ystr) {
+    yvar = input->variable->find(ystr);
+    if (yvar < 0) error->all("Variable name for fix addtorque does not exist");
+    if (input->variable->equalstyle(yvar)) ystyle = EQUAL;
+    else error->all("Variable for fix addtorque is invalid style");
+  }
+  if (zstr) {
+    zvar = input->variable->find(zstr);
+    if (zvar < 0) error->all("Variable name for fix addtorque does not exist");
+    if (input->variable->equalstyle(zvar)) zstyle = EQUAL;
+    else error->all("Variable for fix addtorque is invalid style");
+  }
+
+  if (xstyle == EQUAL || ystyle == EQUAL || zstyle == EQUAL)
+    varflag = EQUAL;
+  else varflag = CONSTANT;
+
+  if (strcmp(update->integrate_style,"respa") == 0)
+    nlevels_respa = ((Respa *) update->integrate)->nlevels;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixAddTorque::setup(int vflag)
+{
+  if (strcmp(update->integrate_style,"verlet") == 0)
+    post_force(vflag);
+  else {
+    ((Respa *) update->integrate)->copy_flevel_f(nlevels_respa-1);
+    post_force_respa(vflag,nlevels_respa-1,0);
+    ((Respa *) update->integrate)->copy_f_flevel(nlevels_respa-1);
+  }
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixAddTorque::min_setup(int vflag)
+{
+  post_force(vflag);
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixAddTorque::post_force(int vflag)
+{
+  double **x = atom->x;
+  double **f = atom->f;
+  int *mask = atom->mask;
+  int *type = atom->type;
+  int *image = atom->image;
+  double *mass = atom->mass;
+  double *rmass = atom->rmass;
+  int nlocal = atom->nlocal;
+  double mvv2e = force->mvv2e;
+  
+  int xbox,ybox,zbox;
+  double dx,dy,dz,vx,vy,vz,fx,fy,fz,massone,omegadotr;
+  double xprd = domain->xprd;
+  double yprd = domain->yprd;
+  double zprd = domain->zprd;
+
+  double tcm[3],xcm[3],angmom[3],omega[3],itorque[3],domegadt[3],tlocal[3];
+  double inertia[3][3];
+  // foriginal[0] = "potential energy" for added force
+  // foriginal[123] = torque on atoms before extra force added
+  foriginal[0] = foriginal[1] = foriginal[2] = foriginal[3] = 0.0;
+  force_flag = 0;
+  
+  if (varflag == EQUAL) {
+    // variable torque, wrap with clear/add
+    modify->clearstep_compute();
+    if (xstyle == EQUAL) xvalue = input->variable->compute_equal(xvar);
+    if (ystyle == EQUAL) yvalue = input->variable->compute_equal(yvar);
+    if (zstyle == EQUAL) zvalue = input->variable->compute_equal(zvar);
+    modify->addstep_compute(update->ntimestep + 1);
+  }
+  
+  atom->check_mass();
+  double masstotal = group->mass(igroup);
+  group->xcm(igroup,masstotal,xcm);
+  group->inertia(igroup,xcm,inertia);
+  group->angmom(igroup,xcm,angmom);
+  group->omega(angmom,inertia,omega);
+
+  tlocal[0] = tlocal[1] = tlocal[2] = 0.0;
+  for (int i = 0; i < nlocal; i++)
+    if (mask[i] & groupbit) {
+      xbox = (image[i] & 1023) - 512;
+      ybox = (image[i] >> 10 & 1023) - 512;
+      zbox = (image[i] >> 20) - 512;
+      dx = (x[i][0] + xbox*xprd) - xcm[0];
+      dy = (x[i][1] + ybox*yprd) - xcm[1];
+      dz = (x[i][2] + zbox*zprd) - xcm[2];
+      if (rmass) massone = rmass[i];
+      else massone = mass[type[i]];
+      omegadotr = omega[0]*dx+omega[1]*dy+omega[2]*dz;
+      tlocal[0] += massone * omegadotr * (dy*omega[2] - dz*omega[1]);
+      tlocal[1] += massone * omegadotr * (dz*omega[0] - dx*omega[2]);
+      tlocal[2] += massone * omegadotr * (dx*omega[1] - dy*omega[0]);
+    }
+  MPI_Allreduce(tlocal,itorque,3,MPI_DOUBLE,MPI_SUM,world);
+  
+  tcm[0] = xvalue - mvv2e*itorque[0];
+  tcm[1] = yvalue - mvv2e*itorque[1];
+  tcm[2] = zvalue - mvv2e*itorque[2];
+  group->omega(tcm,inertia,domegadt);
+  
+  for (int i = 0; i < nlocal; i++)
+    if (mask[i] & groupbit) {
+      xbox = (image[i] & 1023) - 512;
+      ybox = (image[i] >> 10 & 1023) - 512;
+      zbox = (image[i] >> 20) - 512;
+      dx = (x[i][0] + xbox*xprd) - xcm[0];
+      dy = (x[i][1] + ybox*yprd) - xcm[1];
+      dz = (x[i][2] + zbox*zprd) - xcm[2];
+      vx = mvv2e*(dz*omega[1]-dy*omega[2]);
+      vy = mvv2e*(dx*omega[2]-dz*omega[0]);
+      vz = mvv2e*(dy*omega[0]-dx*omega[1]);
+      if (rmass) massone = rmass[i];
+      else massone = mass[type[i]];
+      fx = massone * (dz*domegadt[1]-dy*domegadt[2] + vz*omega[1]-vy*omega[2]);
+      fy = massone * (dx*domegadt[2]-dz*domegadt[0] + vx*omega[2]-vz*omega[0]);
+      fz = massone * (dy*domegadt[0]-dx*domegadt[1] + vy*omega[0]-vx*omega[1]);
+      
+      // potential energy = - x dot f
+      foriginal[0] -= fx*x[i][0] + fy*x[i][1] + fz*x[i][2];
+      foriginal[1] += dy*f[i][2] - dz*f[i][1];
+      foriginal[2] += dz*f[i][0] - dx*f[i][2];
+      foriginal[3] += dx*f[i][1] - dy*f[i][0];
+      f[i][0] += fx;
+      f[i][1] += fy;
+      f[i][2] += fz;
+    }
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixAddTorque::post_force_respa(int vflag, int ilevel, int iloop)
+{
+  if (ilevel == nlevels_respa-1) post_force(vflag);
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixAddTorque::min_post_force(int vflag)
+{
+  post_force(vflag);
+}
+
+/* ----------------------------------------------------------------------
+   potential energy of added torque
+------------------------------------------------------------------------- */
+
+double FixAddTorque::compute_scalar()
+{
+  // only sum across procs one time
+
+  if (force_flag == 0) {
+    MPI_Allreduce(foriginal,foriginal_all,4,MPI_DOUBLE,MPI_SUM,world);
+    force_flag = 1;
+  }
+  return foriginal_all[0];
+}
+
+/* ----------------------------------------------------------------------
+   return components of total torque on fix group before torque was changed
+------------------------------------------------------------------------- */
+
+double FixAddTorque::compute_vector(int n)
+{
+  // only sum across procs one time
+
+  if (force_flag == 0) {
+    MPI_Allreduce(foriginal,foriginal_all,4,MPI_DOUBLE,MPI_SUM,world);
+    force_flag = 1;
+  }
+  return foriginal_all[n+1];
+}

src/USER-MISC/fix_addtorque.h

@@ -0,0 +1,54 @@
+/* ----------------------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   http://lammps.sandia.gov, Sandia National Laboratories
+   Steve Plimpton, sjplimp@sandia.gov
+
+   Copyright (2003) Sandia Corporation.  Under the terms of Contract
+   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
+   certain rights in this software.  This software is distributed under 
+   the GNU General Public License.
+
+   See the README file in the top-level LAMMPS directory.
+------------------------------------------------------------------------- */
+
+#ifdef FIX_CLASS
+
+FixStyle(addtorque,FixAddTorque)
+
+#else
+
+#ifndef LMP_FIX_ADDTORQUE_H
+#define LMP_FIX_ADDTORQUE_H
+
+#include "fix.h"
+
+namespace LAMMPS_NS {
+
+class FixAddTorque : public Fix {
+ public:
+  FixAddTorque(class LAMMPS *, int, char **);
+  ~FixAddTorque();
+  int setmask();
+  void init();
+  void setup(int);
+  void min_setup(int);
+  void post_force(int);
+  void post_force_respa(int, int, int);
+  void min_post_force(int);
+  double compute_scalar();
+  double compute_vector(int);
+
+ private:
+  double xvalue,yvalue,zvalue;
+  int varflag;
+  char *xstr,*ystr,*zstr;
+  int xvar,yvar,zvar,xstyle,ystyle,zstyle;
+  double foriginal[4],foriginal_all[4];
+  int force_flag;
+  int nlevels_respa;
+};
+
+}
+
+#endif
+#endif