diff --git a/src/fix_external.cpp b/src/fix_external.cpp
index ab942f874..a3b697bb2 100644
--- a/src/fix_external.cpp
+++ b/src/fix_external.cpp
@@ -1,345 +1,347 @@
 /* ----------------------------------------------------------------------
    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 <stdio.h>
 #include <string.h>
 #include <stdlib.h>
 #include "fix_external.h"
 #include "atom.h"
 #include "update.h"
 #include "memory.h"
 #include "error.h"
 #include "force.h"
 
 using namespace LAMMPS_NS;
 using namespace FixConst;
 
 enum{PF_CALLBACK,PF_ARRAY};
 
 /* ---------------------------------------------------------------------- */
 
 FixExternal::FixExternal(LAMMPS *lmp, int narg, char **arg) :
   Fix(lmp, narg, arg),
   fexternal(NULL), caller_vector(NULL)
 {
   if (narg < 4) error->all(FLERR,"Illegal fix external command");
 
   scalar_flag = 1;
   global_freq = 1;
   virial_flag = 1;
   thermo_virial = 1;
   extscalar = 1;
 
   if (strcmp(arg[3],"pf/callback") == 0) {
     if (narg != 6) error->all(FLERR,"Illegal fix external command");
     mode = PF_CALLBACK;
     ncall = force->inumeric(FLERR,arg[4]);
     napply = force->inumeric(FLERR,arg[5]);
     if (ncall <= 0 || napply <= 0)
       error->all(FLERR,"Illegal fix external command");
   } else if (strcmp(arg[3],"pf/array") == 0) {
     if (narg != 5) error->all(FLERR,"Illegal fix external command");
     mode = PF_ARRAY;
     napply = force->inumeric(FLERR,arg[4]);
     if (napply <= 0) error->all(FLERR,"Illegal fix external command");
   } else error->all(FLERR,"Illegal fix external command");
 
   callback = NULL;
 
   // perform initial allocation of atom-based array
   // register with Atom class
 
   grow_arrays(atom->nmax);
   atom->add_callback(0);
 
   user_energy = 0.0;
 
   // optional vector of values provided by caller
   // vector_flag and size_vector are setup via set_vector_length()
 
   caller_vector = NULL;
 }
 
 /* ---------------------------------------------------------------------- */
 
 FixExternal::~FixExternal()
 {
   // unregister callbacks to this fix from Atom class
 
   atom->delete_callback(id,0);
 
   memory->destroy(fexternal);
   delete [] caller_vector;
 }
 
 /* ---------------------------------------------------------------------- */
 
 int FixExternal::setmask()
 {
   int mask = 0;
   if (mode == PF_CALLBACK || mode == PF_ARRAY) {
     mask |= PRE_REVERSE;
     mask |= POST_FORCE;
     mask |= THERMO_ENERGY;
     mask |= MIN_POST_FORCE;
   }
   return mask;
 }
 
 /* ---------------------------------------------------------------------- */
 
 void FixExternal::init()
 {
   if (mode == PF_CALLBACK && callback == NULL)
     error->all(FLERR,"Fix external callback function not set");
 }
 
 /* ---------------------------------------------------------------------- */
 
 void FixExternal::setup(int vflag)
 {
   post_force(vflag);
 }
 
 /* --------------------------------------------------------------------- */
 
 void FixExternal::setup_pre_reverse(int eflag, int vflag)
 {
   pre_reverse(eflag,vflag);
 }
 
 /* ---------------------------------------------------------------------- */
 
 void FixExternal::min_setup(int vflag)
 {
   post_force(vflag);
 }
 
 /* ----------------------------------------------------------------------
    store eflag, so can use it in post_force to tally per-atom energies
 ------------------------------------------------------------------------- */
 
 void FixExternal::pre_reverse(int eflag, int vflag)
 {
   eflag_caller = eflag;
 }
 
 /* ---------------------------------------------------------------------- */
 
 void FixExternal::post_force(int vflag)
 {
   bigint ntimestep = update->ntimestep;
 
   int eflag = eflag_caller;
   if (eflag || vflag) ev_setup(eflag,vflag);
   else evflag = 0;
 
   // invoke the callback in driver program
   // it will fill fexternal with forces
 
   if (mode == PF_CALLBACK && ntimestep % ncall == 0)
     (this->callback)(ptr_caller,update->ntimestep,
                      atom->nlocal,atom->tag,atom->x,fexternal);
 
   // add forces from fexternal to atoms in group
 
   if (ntimestep % napply == 0) {
     double **f = atom->f;
     int *mask = atom->mask;
     int nlocal = atom->nlocal;
 
     for (int i = 0; i < nlocal; i++)
       if (mask[i] & groupbit) {
         f[i][0] += fexternal[i][0];
         f[i][1] += fexternal[i][1];
         f[i][2] += fexternal[i][2];
       }
   }
 }
 
 /* ---------------------------------------------------------------------- */
 
 void FixExternal::min_post_force(int vflag)
 {
   post_force(vflag);
 }
 
 // ----------------------------------------------------------------------
 // "set" methods caller can invoke directly
 // ----------------------------------------------------------------------
 
 /* ----------------------------------------------------------------------
    caller invokes this method to set its contribution to global energy
    unlike other energy/virial set methods:
      do not just return if eflag_global is not set
      b/c input script could access this quantity via compute_scalar()
      even if eflag is not set on a particular timestep
 ------------------------------------------------------------------------- */
 
 void FixExternal::set_energy_global(double caller_energy)
 {
   user_energy = caller_energy;
 }
 
 /* ----------------------------------------------------------------------
    caller invokes this method to set its contribution to global virial
 ------------------------------------------------------------------------- */
 
 void FixExternal::set_virial_global(double *caller_virial)
 {
+  if (!evflag) return;
   if (!vflag_global) return;
 
   for (int i = 0; i < 6; i++)
     virial[i] = caller_virial[i];
 }
 
 /* ----------------------------------------------------------------------
    caller invokes this method to set its contribution to peratom energy
 ------------------------------------------------------------------------- */
 
 void FixExternal::set_energy_peratom(double *caller_energy)
 {
   if (!eflag_atom) return;
 
   int nlocal = atom->nlocal;
   for (int i = 0; i < nlocal; i++)
     eatom[i] = caller_energy[i];
 }
 
 /* ----------------------------------------------------------------------
    caller invokes this method to set its contribution to peratom virial
 ------------------------------------------------------------------------- */
 
 void FixExternal::set_virial_peratom(double **caller_virial)
 {
   int i,j;
 
+  if (!evflag) return;
   if (!vflag_atom) return;
 
   int nlocal = atom->nlocal;
   for (i = 0; i < nlocal; i++)
     for (j = 0; j < 6; j++)
       vatom[i][j] = caller_virial[i][j];
 }
 
 /* ----------------------------------------------------------------------
    caller invokes this method to set length of vector of values
    assume all vector values are extensive, could make this an option
 ------------------------------------------------------------------------- */
 
 void FixExternal::set_vector_length(int n)
 {
   delete [] caller_vector;
 
   vector_flag = 1;
   size_vector = n;
   extvector = 1;
 
   caller_vector = new double[n];
 }
 
 /* ----------------------------------------------------------------------
    caller invokes this method to set Index value in vector
    index ranges from 1 to N inclusive
 ------------------------------------------------------------------------- */
 
 void FixExternal::set_vector(int index, double value)
 {
   if (index >= size_vector)
     error->all(FLERR,"Invalid set_vector index in fix external");
   caller_vector[index-1] = value;
 }
 
 /* ----------------------------------------------------------------------
    potential energy of added force
    up to user to set it via set_energy()
 ------------------------------------------------------------------------- */
 
 double FixExternal::compute_scalar()
 {
   return user_energy;
 }
 
 /* ----------------------------------------------------------------------
    arbitrary value computed by caller
    up to user to set it via set_vector()
 ------------------------------------------------------------------------- */
 
 double FixExternal::compute_vector(int n)
 {
   return caller_vector[n];
 }
 
 /* ----------------------------------------------------------------------
    memory usage of local atom-based array
 ------------------------------------------------------------------------- */
 
 double FixExternal::memory_usage()
 {
   double bytes = 3*atom->nmax * sizeof(double);
   return bytes;
 }
 
 /* ----------------------------------------------------------------------
    allocate atom-based array
 ------------------------------------------------------------------------- */
 
 void FixExternal::grow_arrays(int nmax)
 {
   memory->grow(fexternal,nmax,3,"external:fexternal");
 }
 
 /* ----------------------------------------------------------------------
    copy values within local atom-based array
 ------------------------------------------------------------------------- */
 
 void FixExternal::copy_arrays(int i, int j, int delflag)
 {
   fexternal[j][0] = fexternal[i][0];
   fexternal[j][1] = fexternal[i][1];
   fexternal[j][2] = fexternal[i][2];
 }
 
 /* ----------------------------------------------------------------------
    pack values in local atom-based array for exchange with another proc
 ------------------------------------------------------------------------- */
 
 int FixExternal::pack_exchange(int i, double *buf)
 {
   buf[0] = fexternal[i][0];
   buf[1] = fexternal[i][1];
   buf[2] = fexternal[i][2];
   return 3;
 }
 
 /* ----------------------------------------------------------------------
    unpack values in local atom-based array from exchange with another proc
 ------------------------------------------------------------------------- */
 
 int FixExternal::unpack_exchange(int nlocal, double *buf)
 {
   fexternal[nlocal][0] = buf[0];
   fexternal[nlocal][1] = buf[1];
   fexternal[nlocal][2] = buf[2];
   return 3;
 }
 
 /* ----------------------------------------------------------------------
    external caller sets a callback function to invoke in post_force()
 ------------------------------------------------------------------------- */
 
 void FixExternal::set_callback(FnPtr caller_callback, void *caller_ptr)
 {
   callback = caller_callback;
   ptr_caller = caller_ptr;
 }