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fix_temp_rescale_eff.cpp
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Mon, Nov 11, 13:51

fix_temp_rescale_eff.cpp
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/* ----------------------------------------------------------------------
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: Andres Jaramillo-Botero
------------------------------------------------------------------------- */
#include "string.h"
#include "stdlib.h"
#include "math.h"
#include "fix_temp_rescale_eff.h"
#include "atom.h"
#include "force.h"
#include "group.h"
#include "update.h"
#include "domain.h"
#include "region.h"
#include "comm.h"
#include "modify.h"
#include "compute.h"
#include "error.h"
using namespace LAMMPS_NS;
using namespace FixConst;
enum{NOBIAS,BIAS};
/* ---------------------------------------------------------------------- */
FixTempRescaleEff::FixTempRescaleEff(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg)
{
if (narg < 8) error->all(FLERR,"Illegal fix temp/rescale/eff command");
nevery = force->inumeric(FLERR,arg[3]);
if (nevery <= 0) error->all(FLERR,"Illegal fix temp/rescale/eff command");
scalar_flag = 1;
global_freq = nevery;
extscalar = 1;
t_start = force->numeric(FLERR,arg[4]);
t_stop = force->numeric(FLERR,arg[5]);
t_window = force->numeric(FLERR,arg[6]);
fraction = force->numeric(FLERR,arg[7]);
// create a new compute temp/eff
// id = fix-ID + temp, compute group = fix group
int n = strlen(id) + 6;
id_temp = new char[n];
strcpy(id_temp,id);
strcat(id_temp,"_temp");
char **newarg = new char*[6];
newarg[0] = id_temp;
newarg[1] = group->names[igroup];
newarg[2] = (char *) "temp/eff";
modify->add_compute(3,newarg);
delete [] newarg;
tflag = 1;
energy = 0.0;
}
/* ---------------------------------------------------------------------- */
FixTempRescaleEff::~FixTempRescaleEff()
{
// delete temperature if fix created it
if (tflag) modify->delete_compute(id_temp);
delete [] id_temp;
}
/* ---------------------------------------------------------------------- */
int FixTempRescaleEff::setmask()
{
int mask = 0;
mask |= END_OF_STEP;
mask |= THERMO_ENERGY;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixTempRescaleEff::init()
{
int icompute = modify->find_compute(id_temp);
if (icompute < 0)
error->all(FLERR,"Temperature ID for fix temp/rescale/eff does not exist");
temperature = modify->compute[icompute];
if (temperature->tempbias) which = BIAS;
else which = NOBIAS;
}
/* ---------------------------------------------------------------------- */
void FixTempRescaleEff::end_of_step()
{
double t_current = temperature->compute_scalar();
if (t_current == 0.0)
error->all(FLERR,"Computed temperature for fix temp/rescale/eff cannot be 0.0");
double delta = update->ntimestep - update->beginstep;
delta /= update->endstep - update->beginstep;
double t_target = t_start + delta * (t_stop-t_start);
// rescale velocity of appropriate atoms if outside window
// for BIAS:
// temperature is current, so do not need to re-compute
// OK to not test returned v = 0, since factor is multiplied by v
if (fabs(t_current-t_target) > t_window) {
t_target = t_current - fraction*(t_current-t_target);
double factor = sqrt(t_target/t_current);
double efactor = 0.5 * force->boltz * temperature->dof;
double **v = atom->v;
int *mask = atom->mask;
int nlocal = atom->nlocal;
int *spin = atom->spin;
double *ervel = atom->ervel;
if (which == NOBIAS) {
energy += (t_current-t_target) * efactor;
for (int i = 0; i < nlocal; i++) {
if (mask[i] & groupbit) {
v[i][0] *= factor;
v[i][1] *= factor;
v[i][2] *= factor;
if (abs(spin[i])==1)
ervel[i] *= factor;
}
}
} else {
energy += (t_current-t_target) * efactor;
for (int i = 0; i < nlocal; i++) {
if (mask[i] & groupbit) {
temperature->remove_bias(i,v[i]);
v[i][0] *= factor;
v[i][1] *= factor;
v[i][2] *= factor;
if (abs(spin[i])==1)
ervel[i] *= factor;
temperature->restore_bias(i,v[i]);
}
}
}
}
}
/* ---------------------------------------------------------------------- */
int FixTempRescaleEff::modify_param(int narg, char **arg)
{
if (strcmp(arg[0],"temp/eff") == 0) {
if (narg < 2) error->all(FLERR,"Illegal fix_modify command");
if (tflag) {
modify->delete_compute(id_temp);
tflag = 0;
}
delete [] id_temp;
int n = strlen(arg[1]) + 1;
id_temp = new char[n];
strcpy(id_temp,arg[1]);
int icompute = modify->find_compute(id_temp);
if (icompute < 0) error->all(FLERR,"Could not find fix_modify temperature ID");
temperature = modify->compute[icompute];
if (temperature->tempflag == 0)
error->all(FLERR,"Fix_modify temperature ID does not compute temperature");
if (temperature->igroup != igroup && comm->me == 0)
error->warning(FLERR,"Group for fix_modify temp != fix group");
return 2;
}
return 0;
}
/* ---------------------------------------------------------------------- */
void FixTempRescaleEff::reset_target(double t_new)
{
t_start = t_stop = t_new;
}
/* ---------------------------------------------------------------------- */
double FixTempRescaleEff::compute_scalar()
{
return energy;
}

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