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pair_lj_expand_omp.cpp
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Wed, Feb 19, 00:09

pair_lj_expand_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
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 "math.h"
#include "pair_lj_expand_omp.h"
#include "atom.h"
#include "comm.h"
#include "force.h"
#include "neighbor.h"
#include "neigh_list.h"
using namespace LAMMPS_NS;
/* ---------------------------------------------------------------------- */
PairLJExpandOMP::PairLJExpandOMP(LAMMPS *lmp) :
PairLJExpand(lmp), ThrOMP(lmp, PAIR)
{
respa_enable = 0;
}
/* ---------------------------------------------------------------------- */
void PairLJExpandOMP::compute(int eflag, int vflag)
{
if (eflag || vflag) {
ev_setup(eflag,vflag);
ev_setup_thr(this);
} else evflag = vflag_fdotr = 0;
const int nall = atom->nlocal + atom->nghost;
const int nthreads = comm->nthreads;
const int inum = list->inum;
#if defined(_OPENMP)
#pragma omp parallel default(shared)
#endif
{
int ifrom, ito, tid;
double **f;
f = loop_setup_thr(atom->f, ifrom, ito, tid, inum, nall, nthreads);
if (evflag) {
if (eflag) {
if (force->newton_pair) eval<1,1,1>(f, ifrom, ito, tid);
else eval<1,1,0>(f, ifrom, ito, tid);
} else {
if (force->newton_pair) eval<1,0,1>(f, ifrom, ito, tid);
else eval<1,0,0>(f, ifrom, ito, tid);
}
} else {
if (force->newton_pair) eval<0,0,1>(f, ifrom, ito, tid);
else eval<0,0,0>(f, ifrom, ito, tid);
}
// reduce per thread forces into global force array.
data_reduce_thr(&(atom->f[0][0]), nall, nthreads, 3, tid);
} // end of omp parallel region
// reduce per thread energy and virial, if requested.
if (evflag) ev_reduce_thr(this);
if (vflag_fdotr) virial_fdotr_compute();
}
template <int EVFLAG, int EFLAG, int NEWTON_PAIR>
void PairLJExpandOMP::eval(double **f, int iifrom, int iito, int tid)
{
int i,j,ii,jj,jnum,itype,jtype;
double xtmp,ytmp,ztmp,delx,dely,delz,evdwl,fpair;
double rsq,r2inv,r6inv,forcelj,factor_lj;
double r,rshift,rshiftsq;
int *ilist,*jlist,*numneigh,**firstneigh;
evdwl = 0.0;
double **x = atom->x;
int *type = atom->type;
int nlocal = atom->nlocal;
double *special_lj = force->special_lj;
double fxtmp,fytmp,fztmp;
ilist = list->ilist;
numneigh = list->numneigh;
firstneigh = list->firstneigh;
// loop over neighbors of my atoms
for (ii = iifrom; ii < iito; ++ii) {
i = ilist[ii];
xtmp = x[i][0];
ytmp = x[i][1];
ztmp = x[i][2];
itype = type[i];
jlist = firstneigh[i];
jnum = numneigh[i];
fxtmp=fytmp=fztmp=0.0;
for (jj = 0; jj < jnum; jj++) {
j = jlist[jj];
factor_lj = special_lj[sbmask(j)];
j &= NEIGHMASK;
delx = xtmp - x[j][0];
dely = ytmp - x[j][1];
delz = ztmp - x[j][2];
rsq = delx*delx + dely*dely + delz*delz;
jtype = type[j];
if (rsq < cutsq[itype][jtype]) {
r = sqrt(rsq);
rshift = r - shift[itype][jtype];
rshiftsq = rshift*rshift;
r2inv = 1.0/rshiftsq;
r6inv = r2inv*r2inv*r2inv;
forcelj = r6inv * (lj1[itype][jtype]*r6inv - lj2[itype][jtype]);
fpair = factor_lj*forcelj/rshift/r;
fxtmp += delx*fpair;
fytmp += dely*fpair;
fztmp += delz*fpair;
if (NEWTON_PAIR || j < nlocal) {
f[j][0] -= delx*fpair;
f[j][1] -= dely*fpair;
f[j][2] -= delz*fpair;
}
if (EFLAG) {
evdwl = r6inv*(lj3[itype][jtype]*r6inv-lj4[itype][jtype])
- offset[itype][jtype];
evdwl *= factor_lj;
}
if (EVFLAG) ev_tally_thr(this, i,j,nlocal,NEWTON_PAIR,
evdwl,0.0,fpair,delx,dely,delz,tid);
}
}
f[i][0] += fxtmp;
f[i][1] += fytmp;
f[i][2] += fztmp;
}
}
/* ---------------------------------------------------------------------- */
double PairLJExpandOMP::memory_usage()
{
double bytes = memory_usage_thr();
bytes += PairLJExpand::memory_usage();
return bytes;
}

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