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pair_lj_charmm_coul_long_soft_omp.cpp
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Wed, Aug 21, 14:16

pair_lj_charmm_coul_long_soft_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_charmm_coul_long_soft_omp.h"
#include "atom.h"
#include "comm.h"
#include "force.h"
#include "neighbor.h"
#include "neigh_list.h"
#include "suffix.h"
using namespace LAMMPS_NS;
/* ---------------------------------------------------------------------- */
PairLJCharmmCoulLongSoftOMP::PairLJCharmmCoulLongSoftOMP(LAMMPS *lmp) :
PairLJCharmmCoulLongSoft(lmp), ThrOMP(lmp, THR_PAIR)
{
suffix_flag |= Suffix::OMP;
respa_enable = 0;
cut_respa = NULL;
}
/* ---------------------------------------------------------------------- */
void PairLJCharmmCoulLongSoftOMP::compute(int eflag, int vflag)
{
if (eflag || vflag) {
ev_setup(eflag,vflag);
} 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(none) shared(eflag,vflag)
#endif
{
int ifrom, ito, tid;
loop_setup_thr(ifrom, ito, tid, inum, nthreads);
ThrData *thr = fix->get_thr(tid);
ev_setup_thr(eflag, vflag, nall, eatom, vatom, thr);
if (evflag) {
if (eflag) {
if (force->newton_pair) eval<1,1,1>(ifrom, ito, thr);
else eval<1,1,0>(ifrom, ito, thr);
} else {
if (force->newton_pair) eval<1,0,1>(ifrom, ito, thr);
else eval<1,0,0>(ifrom, ito, thr);
}
} else {
if (force->newton_pair) eval<0,0,1>(ifrom, ito, thr);
else eval<0,0,0>(ifrom, ito, thr);
}
reduce_thr(this, eflag, vflag, thr);
} // end of omp parallel region
}
/* ---------------------------------------------------------------------- */
template <int EVFLAG, int EFLAG, int NEWTON_PAIR>
void PairLJCharmmCoulLongSoftOMP::eval(int iifrom, int iito, ThrData * const thr)
{
const dbl3_t * _noalias const x = (dbl3_t *) atom->x[0];
dbl3_t * _noalias const f = (dbl3_t *) thr->get_f()[0];
const double * _noalias const q = atom->q;
const int * _noalias const type = atom->type;
const double * _noalias const special_coul = force->special_coul;
const double * _noalias const special_lj = force->special_lj;
const double qqrd2e = force->qqrd2e;
const double inv_denom_lj = 1.0/denom_lj;
const int * const ilist = list->ilist;
const int * const numneigh = list->numneigh;
const int * const * const firstneigh = list->firstneigh;
const int nlocal = atom->nlocal;
// loop over neighbors of my atoms
for (int ii = iifrom; ii < iito; ++ii) {
const int i = ilist[ii];
const int itype = type[i];
const double qtmp = q[i];
const double xtmp = x[i].x;
const double ytmp = x[i].y;
const double ztmp = x[i].z;
double fxtmp,fytmp,fztmp;
fxtmp=fytmp=fztmp=0.0;
const int * const jlist = firstneigh[i];
const int jnum = numneigh[i];
const double * _noalias const lj1i = lj1[itype];
const double * _noalias const lj2i = lj2[itype];
const double * _noalias const lj3i = lj3[itype];
const double * _noalias const lj4i = lj4[itype];
const double * _noalias const epsii = epsilon[itype];
for (int jj = 0; jj < jnum; jj++) {
double forcecoul, forcelj, evdwl, ecoul;
forcecoul = forcelj = evdwl = ecoul = 0.0;
const int sbindex = sbmask(jlist[jj]);
const int j = jlist[jj] & NEIGHMASK;
const double delx = xtmp - x[j].x;
const double dely = ytmp - x[j].y;
const double delz = ztmp - x[j].z;
const double rsq = delx*delx + dely*dely + delz*delz;
const int jtype = type[j];
if (rsq < cutsq[itype][jtype]) {
const double r2inv = 1.0/rsq;
if (rsq < cut_coulsq) {
const double A1 = 0.254829592;
const double A2 = -0.284496736;
const double A3 = 1.421413741;
const double A4 = -1.453152027;
const double A5 = 1.061405429;
const double EWALD_F = 1.12837917;
const double INV_EWALD_P = 1.0/0.3275911;
const double r = sqrt(rsq);
const double grij = g_ewald * r;
const double expm2 = exp(-grij*grij);
const double t = INV_EWALD_P / (INV_EWALD_P + grij);
const double erfc = t * (A1+t*(A2+t*(A3+t*(A4+t*A5)))) * expm2;
const double denc = sqrt(lj4i[jtype] + rsq);
const double prefactor = qqrd2e * lj1i[jtype] * qtmp*q[j] / (denc*denc*denc);
forcecoul = prefactor * (erfc + EWALD_F*grij*expm2);
if (EFLAG) ecoul = prefactor*erfc*denc*denc;
if (sbindex) {
const double adjust = (1.0-special_coul[sbindex])*prefactor;
forcecoul -= adjust;
if (EFLAG) ecoul -= adjust*denc*denc;
}
}
if (rsq < cut_ljsq) {
const double r4sig6 = rsq*rsq / lj2i[jtype];
const double denlj = lj3i[jtype] + rsq*r4sig6;
forcelj = lj1i[jtype] * epsii[jtype] *
(48.0*r4sig6/(denlj*denlj*denlj) - 24.0*r4sig6/(denlj*denlj));
const double philj = lj1i[jtype] * 4.0 * epsii[jtype]
* (1.0/(denlj*denlj) - 1.0/denlj);
if (EFLAG) evdwl = philj;
if (rsq > cut_lj_innersq) {
const double drsq = cut_ljsq - rsq;
const double cut2 = (rsq - cut_lj_innersq) * drsq;
const double switch1 = drsq * (drsq*drsq + 3.0*cut2) * inv_denom_lj;
const double switch2 = 12.0 * cut2 * inv_denom_lj;
forcelj = forcelj*switch1 + philj*switch2;
if (EFLAG) evdwl = philj*switch1;
}
if (sbindex) {
const double factor_lj = special_lj[sbindex];
forcelj *= factor_lj;
if (EFLAG) evdwl *= factor_lj;
}
}
const double fpair = forcecoul + forcelj;
fxtmp += delx*fpair;
fytmp += dely*fpair;
fztmp += delz*fpair;
if (NEWTON_PAIR || j < nlocal) {
f[j].x -= delx*fpair;
f[j].y -= dely*fpair;
f[j].z -= delz*fpair;
}
if (EVFLAG) ev_tally_thr(this,i,j,nlocal,NEWTON_PAIR,
evdwl,ecoul,fpair,delx,dely,delz,thr);
}
}
f[i].x += fxtmp;
f[i].y += fytmp;
f[i].z += fztmp;
}
}
/* ---------------------------------------------------------------------- */
double PairLJCharmmCoulLongSoftOMP::memory_usage()
{
double bytes = memory_usage_thr();
bytes += PairLJCharmmCoulLongSoft::memory_usage();
return bytes;
}

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