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fix_ave_force.cpp
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Sat, Aug 10, 10:32

fix_ave_force.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 "mpi.h"
#include "string.h"
#include "stdlib.h"
#include "fix_ave_force.h"
#include "atom.h"
#include "update.h"
#include "respa.h"
#include "error.h"
using namespace LAMMPS_NS;
/* ---------------------------------------------------------------------- */
FixAveForce::FixAveForce(LAMMPS *lmp, int narg, char **arg) :
Fix(lmp, narg, arg)
{
if (narg != 6) error->all("Illegal fix aveforce command");
xflag = yflag = zflag = 1;
if (strcmp(arg[3],"NULL") == 0) xflag = 0;
else xvalue = atof(arg[3]);
if (strcmp(arg[4],"NULL") == 0) yflag = 0;
else yvalue = atof(arg[4]);
if (strcmp(arg[5],"NULL") == 0) zflag = 0;
else zvalue = atof(arg[5]);
}
/* ---------------------------------------------------------------------- */
int FixAveForce::setmask()
{
int mask = 0;
mask |= POST_FORCE;
mask |= POST_FORCE_RESPA;
mask |= MIN_POST_FORCE;
return mask;
}
/* ---------------------------------------------------------------------- */
void FixAveForce::init()
{
if (strcmp(update->integrate_style,"respa") == 0)
nlevels_respa = ((Respa *) update->integrate)->nlevels;
// ncount = total # of atoms in group
int *mask = atom->mask;
int nlocal = atom->nlocal;
int count = 0;
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) count++;
MPI_Allreduce(&count,&ncount,1,MPI_INT,MPI_SUM,world);
}
/* ---------------------------------------------------------------------- */
void FixAveForce::setup()
{
if (strcmp(update->integrate_style,"verlet") == 0)
post_force(1);
else
for (int ilevel = 0; ilevel < nlevels_respa; ilevel++) {
((Respa *) update->integrate)->copy_flevel_f(ilevel);
post_force_respa(1,ilevel,0);
((Respa *) update->integrate)->copy_f_flevel(ilevel);
}
}
/* ---------------------------------------------------------------------- */
void FixAveForce::min_setup()
{
post_force(1);
}
/* ---------------------------------------------------------------------- */
void FixAveForce::post_force(int vflag)
{
// sum forces on participating atoms
double **f = atom->f;
int *mask = atom->mask;
int nlocal = atom->nlocal;
double sum[3];
sum[0] = sum[1] = sum[2] = 0.0;
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
sum[0] += f[i][0];
sum[1] += f[i][1];
sum[2] += f[i][2];
}
// average the force on participating atoms
// add in requested amount
double sumall[3];
MPI_Allreduce(sum,sumall,3,MPI_DOUBLE,MPI_SUM,world);
sumall[0] = sumall[0]/ncount + xvalue;
sumall[1] = sumall[1]/ncount + yvalue;
sumall[2] = sumall[2]/ncount + zvalue;
// set force of all participating atoms to same value
// only for active dimensions
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
if (xflag) f[i][0] = sumall[0];
if (yflag) f[i][1] = sumall[1];
if (zflag) f[i][2] = sumall[2];
}
}
/* ---------------------------------------------------------------------- */
void FixAveForce::post_force_respa(int vflag, int ilevel, int iloop)
{
// ave + extra force on outermost level
// just ave on inner levels
if (ilevel == nlevels_respa-1) post_force(vflag);
else {
double **f = atom->f;
int *mask = atom->mask;
int nlocal = atom->nlocal;
double sum[3];
sum[0] = sum[1] = sum[2] = 0.0;
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
sum[0] += f[i][0];
sum[1] += f[i][1];
sum[2] += f[i][2];
}
double sumall[3];
MPI_Allreduce(sum,sumall,3,MPI_DOUBLE,MPI_SUM,world);
sumall[0] = sumall[0]/ncount;
sumall[1] = sumall[1]/ncount;
sumall[2] = sumall[2]/ncount;
for (int i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
if (xflag) f[i][0] = sumall[0];
if (yflag) f[i][1] = sumall[1];
if (zflag) f[i][2] = sumall[2];
}
}
}
/* ---------------------------------------------------------------------- */
void FixAveForce::min_post_force(int vflag)
{
post_force(vflag);
}

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