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fix_dt_reset.cpp
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Tue, May 28, 02:13
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rLAMMPS lammps
fix_dt_reset.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.
------------------------------------------------------------------------- */
#include "math.h"
#include "stdlib.h"
#include "string.h"
#include "fix_dt_reset.h"
#include "atom.h"
#include "update.h"
#include "integrate.h"
#include "domain.h"
#include "lattice.h"
#include "force.h"
#include "pair.h"
#include "modify.h"
#include "fix.h"
#include "output.h"
#include "dump.h"
#include "comm.h"
#include "error.h"
using namespace LAMMPS_NS;
#define BIG 1.0e20
#define MIN(A,B) ((A) < (B)) ? (A) : (B)
#define MAX(A,B) ((A) > (B)) ? (A) : (B)
/* ---------------------------------------------------------------------- */
FixDtReset::FixDtReset(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg)
{
if (narg < 7) error->all("Illegal fix dt/reset command");
scalar_flag = 1;
vector_flag = 1;
size_vector = 1;
scalar_vector_freq = 1;
extscalar = 0;
extvector = 0;
nevery = atoi(arg[3]);
if (nevery <= 0) error->all("Illegal fix dt/reset command");
minbound = maxbound = 1;
tmin = tmax = 0.0;
if (strcmp(arg[4],"INF") == 0) minbound = 0;
else tmin = atof(arg[4]);
if (strcmp(arg[5],"INF") == 0) maxbound = 0;
else tmax = atof(arg[5]);
xmax = atof(arg[6]);
if (minbound && tmin < 0.0) error->all("Illegal fix dt/reset command");
if (maxbound && tmax < 0.0) error->all("Illegal fix dt/reset command");
if (minbound && maxbound && tmin > tmax)
error->all("Illegal fix dt/reset command");
if (xmax <= 0.0) error->all("Illegal fix dt/reset command");
int scaleflag = 1;
int iarg = 7;
while (iarg < narg) {
if (strcmp(arg[iarg],"units") == 0) {
if (iarg+2 > narg) error->all("Illegal fix dt/reset command");
if (strcmp(arg[iarg+1],"box") == 0) scaleflag = 0;
else if (strcmp(arg[iarg+1],"lattice") == 0) scaleflag = 1;
else error->all("Illegal fix dt/reset command");
iarg += 2;
} else error->all("Illegal fix dt/reset command");
}
// setup scaling, based on xlattice parameter
if (scaleflag && domain->lattice == NULL)
error->all("Use of fix dt/reset with undefined lattice");
if (scaleflag) xmax *= domain->lattice->xlattice;
// initializations
t_elapsed = 0.0;
laststep = update->ntimestep;
}
/* ---------------------------------------------------------------------- */
int FixDtReset::setmask()
{
int mask = 0;
mask |= END_OF_STEP;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixDtReset::init()
{
// set rRESPA flag
respaflag = 0;
if (strcmp(update->integrate_style,"respa") == 0) respaflag = 1;
// check for DCD or XTC dumps
for (int i = 0; i < output->ndump; i++)
if ((strcmp(output->dump[i]->style,"dcd") == 0 ||
strcmp(output->dump[i]->style,"xtc") == 0) && comm->me == 0)
error->warning("Dump dcd/xtc timestamp may be wrong with fix dt/reset");
}
/* ---------------------------------------------------------------------- */
void FixDtReset::setup()
{
end_of_step();
}
/* ---------------------------------------------------------------------- */
void FixDtReset::end_of_step()
{
// accumulate total time based on previous timestep
t_elapsed += (update->ntimestep - laststep) * update->dt;
// compute vmax and amax of any atom in group
double **v = atom->v;
double **f = atom->f;
double *mass = atom->mass;
double *rmass = atom->rmass;
int *type = atom->type;
int *mask = atom->mask;
int nlocal = atom->nlocal;
double vsq,fsq,asq,ms;
double bound[2],bound_all[2];
bound[0] = bound[1] = 0.0;
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
vsq = v[i][0]*v[i][0] + v[i][1]*v[i][1] + v[i][2]*v[i][2];
fsq = f[i][0]*f[i][0] + f[i][1]*f[i][1] + f[i][2]*f[i][2];
if (mass) ms = mass[type[i]];
else ms = rmass[i];
asq = fsq/ms/ms;
bound[0] = MAX(bound[0],vsq);
bound[1] = MAX(bound[1],asq);
}
MPI_Allreduce(bound,bound_all,2,MPI_DOUBLE,MPI_MAX,world);
// set new timestep
double dt,dt1,dt2;
if (bound_all[0] > 0.0) dt1 = xmax/sqrt(bound_all[0]);
else dt1 = BIG;
if (bound_all[1] > 0.0) dt2 = sqrt(2.0 * xmax/sqrt(bound_all[1]));
else dt2 = BIG;
dt = MIN(dt1,dt2);
if (minbound) dt = MAX(dt,tmin);
if (maxbound) dt = MIN(dt,tmax);
// reset update->dt and other classes that depend on it
// rRESPA, pair style, fixes
laststep = update->ntimestep;
if (dt == update->dt) return;
update->dt = dt;
if (respaflag) update->integrate->reset_dt();
if (force->pair) force->pair->reset_dt();
for (int i = 0; i < modify->nfix; i++) modify->fix[i]->reset_dt();
}
/* ---------------------------------------------------------------------- */
double FixDtReset::compute_scalar()
{
return update->dt;
}
/* ---------------------------------------------------------------------- */
double FixDtReset::compute_vector(int n)
{
return t_elapsed;
}
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