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fix_nve_sphere_omp.cpp
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Thu, Jul 4, 00:32

fix_nve_sphere_omp.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 "stdio.h"
#include "string.h"
#include "fix_nve_sphere_omp.h"
#include "atom.h"
#include "atom_vec.h"
#include "update.h"
#include "respa.h"
#include "force.h"
#include "error.h"
using namespace LAMMPS_NS;
#define INERTIA 0.4 // moment of inertia prefactor for sphere
enum{NONE,DIPOLE};
/* ---------------------------------------------------------------------- */
/* ---------------------------------------------------------------------- */
void FixNVESphereOMP::initial_integrate(int vflag)
{
double **x = atom->x;
double **v = atom->v;
double **f = atom->f;
double **omega = atom->omega;
double **torque = atom->torque;
double *radius = atom->radius;
double *rmass = atom->rmass;
int *mask = atom->mask;
int nlocal = atom->nlocal;
int i;
if (igroup == atom->firstgroup) nlocal = atom->nfirst;
// set timestep here since dt may have changed or come via rRESPA
const double dtfrotate = dtf / INERTIA;
// update v,x,omega for all particles
// d_omega/dt = torque / inertia
#if defined(_OPENMP)
#pragma omp parallel for private(i) default(shared)
#endif
for (i = 0; i < nlocal; i++) {
if (mask[i] & groupbit) {
const double dtfm = dtf / rmass[i];
v[i][0] += dtfm * f[i][0];
v[i][1] += dtfm * f[i][1];
v[i][2] += dtfm * f[i][2];
x[i][0] += dtv * v[i][0];
x[i][1] += dtv * v[i][1];
x[i][2] += dtv * v[i][2];
const double dtirotate = dtfrotate / (radius[i]*radius[i]*rmass[i]);
omega[i][0] += dtirotate * torque[i][0];
omega[i][1] += dtirotate * torque[i][1];
omega[i][2] += dtirotate * torque[i][2];
}
}
// update mu for dipoles
// d_mu/dt = omega cross mu
// renormalize mu to dipole length
if (extra == DIPOLE) {
double **mu = atom->mu;
#if defined(_OPENMP)
#pragma omp parallel for private(i) default(shared)
#endif
for (i = 0; i < nlocal; i++) {
double g0,g1,g2,msq,scale;
if (mask[i] & groupbit) {
if (mu[i][3] > 0.0) {
g0 = mu[i][0] + dtv * (omega[i][1]*mu[i][2]-omega[i][2]*mu[i][1]);
g1 = mu[i][1] + dtv * (omega[i][2]*mu[i][0]-omega[i][0]*mu[i][2]);
g2 = mu[i][2] + dtv * (omega[i][0]*mu[i][1]-omega[i][1]*mu[i][0]);
msq = g0*g0 + g1*g1 + g2*g2;
scale = mu[i][3]/sqrt(msq);
mu[i][0] = g0*scale;
mu[i][1] = g1*scale;
mu[i][2] = g2*scale;
}
}
}
}
}
/* ---------------------------------------------------------------------- */
void FixNVESphereOMP::final_integrate()
{
double **v = atom->v;
double **f = atom->f;
double **omega = atom->omega;
double **torque = atom->torque;
double *rmass = atom->rmass;
double *radius = atom->radius;
int *mask = atom->mask;
int nlocal = atom->nlocal;
int i;
if (igroup == atom->firstgroup) nlocal = atom->nfirst;
// set timestep here since dt may have changed or come via rRESPA
const double dtfrotate = dtf / INERTIA;
// update v,omega for all particles
// d_omega/dt = torque / inertia
#if defined(_OPENMP)
#pragma omp parallel for private(i) default(shared)
#endif
for (i = 0; i < nlocal; i++)
if (mask[i] & groupbit) {
const double dtfm = dtf / rmass[i];
v[i][0] += dtfm * f[i][0];
v[i][1] += dtfm * f[i][1];
v[i][2] += dtfm * f[i][2];
const double dtirotate = dtfrotate / (radius[i]*radius[i]*rmass[i]);
omega[i][0] += dtirotate * torque[i][0];
omega[i][1] += dtirotate * torque[i][1];
omega[i][2] += dtirotate * torque[i][2];
}
}

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