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angle_dipole_omp.cpp
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Wed, Jun 19, 16:19

angle_dipole_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.
------------------------------------------------------------------------- */
/* ----------------------------------------------------------------------
Contributing author: Axel Kohlmeyer (Temple U)
------------------------------------------------------------------------- */
#include "angle_dipole_omp.h"
#include "atom.h"
#include "comm.h"
#include "error.h"
#include "force.h"
#include "neighbor.h"
#include "domain.h"
#include "math_const.h"
#include <math.h>
#include "suffix.h"
using namespace LAMMPS_NS;
using namespace MathConst;
#define SMALL 0.001
/* ---------------------------------------------------------------------- */
AngleDipoleOMP::AngleDipoleOMP(class LAMMPS *lmp)
: AngleDipole(lmp), ThrOMP(lmp,THR_ANGLE)
{
suffix_flag |= Suffix::OMP;
}
/* ---------------------------------------------------------------------- */
void AngleDipoleOMP::compute(int eflag, int vflag)
{
if (eflag || vflag) {
ev_setup(eflag,vflag);
} else evflag = 0;
if (!force->newton_bond)
error->all(FLERR,"'newton' flag for bonded interactions must be 'on'");
const int nall = atom->nlocal + atom->nghost;
const int nthreads = comm->nthreads;
const int inum = neighbor->nanglelist;
#if defined(_OPENMP)
#pragma omp parallel default(none) shared(eflag,vflag)
#endif
{
int ifrom, ito, tid;
loop_setup_thr(ifrom, ito, tid, inum, nthreads);
ThrData *thr = fix->get_thr(tid);
thr->timer(Timer::START);
ev_setup_thr(eflag, vflag, nall, eatom, vatom, thr);
if (inum > 0) {
if (evflag)
eval<1>(ifrom, ito, thr);
else
eval<0>(ifrom, ito, thr);
}
thr->timer(Timer::BOND);
reduce_thr(this, eflag, vflag, thr);
} // end of omp parallel region
}
template <int EVFLAG>
void AngleDipoleOMP::eval(int nfrom, int nto, ThrData * const thr)
{
int iRef,iDip,iDummy,n,type;
double delx,dely,delz;
double eangle,tangle,fi[3],fj[3];
double r,cosGamma,deltaGamma,kdg,rmu;
double delTx, delTy, delTz;
double fx, fy, fz, fmod, fmod_sqrtff;
const double * const * const x = atom->x; // position vector
const double * const * const mu = atom->mu; // point-dipole components and moment magnitude
double * const * const f = thr->get_f();
double * const * const torque = thr->get_torque();
const int * const * const anglelist = neighbor->anglelist;
const int nlocal = atom->nlocal;
eangle = 0.0;
for (n = nfrom; n < nto; n++) {
iDip = anglelist[n][0]; // dipole whose orientation is to be restrained
iRef = anglelist[n][1]; // reference atom toward which dipole will point
iDummy = anglelist[n][2]; // dummy atom - irrelevant to the interaction
type = anglelist[n][3];
delx = x[iRef][0] - x[iDip][0];
dely = x[iRef][1] - x[iDip][1];
delz = x[iRef][2] - x[iDip][2];
r = sqrt(delx*delx + dely*dely + delz*delz);
rmu = r * mu[iDip][3];
cosGamma = (mu[iDip][0]*delx+mu[iDip][1]*dely+mu[iDip][2]*delz) / rmu;
deltaGamma = cosGamma - cos(gamma0[type]);
kdg = k[type] * deltaGamma;
if (EVFLAG) eangle = kdg * deltaGamma; // energy
tangle = 2.0 * kdg / rmu;
delTx = tangle * (dely*mu[iDip][2] - delz*mu[iDip][1]);
delTy = tangle * (delz*mu[iDip][0] - delx*mu[iDip][2]);
delTz = tangle * (delx*mu[iDip][1] - dely*mu[iDip][0]);
torque[iDip][0] += delTx;
torque[iDip][1] += delTy;
torque[iDip][2] += delTz;
// Force couple that counterbalances dipolar torque
fx = dely*delTz - delz*delTy; // direction (fi): - r x (-T)
fy = delz*delTx - delx*delTz;
fz = delx*delTy - dely*delTx;
fmod = sqrt(delTx*delTx + delTy*delTy + delTz*delTz) / r; // magnitude
fmod_sqrtff = fmod / sqrt(fx*fx + fy*fy + fz*fz);
fi[0] = fx * fmod_sqrtff;
fi[1] = fy * fmod_sqrtff;
fi[2] = fz * fmod_sqrtff;
fj[0] = -fi[0];
fj[1] = -fi[1];
fj[2] = -fi[2];
f[iDip][0] += fj[0];
f[iDip][1] += fj[1];
f[iDip][2] += fj[2];
f[iRef][0] += fi[0];
f[iRef][1] += fi[1];
f[iRef][2] += fi[2];
if (EVFLAG) // virial = rij.fi = 0 (fj = -fi & fk = 0)
ev_tally_thr(this,iRef,iDip,iDummy,nlocal,/* NEWTON_BOND */ 1,
eangle,fi,fj,0.0,0.0,0.0,0.0,0.0,0.0,thr);
}
}

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