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pair_lj_coul_omp.cpp
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Tue, Oct 1, 07:27

pair_lj_coul_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_coul_omp.h"
#include "atom.h"
#include "comm.h"
#include "math_vector.h"
#include "force.h"
#include "neighbor.h"
#include "neigh_list.h"
using namespace LAMMPS_NS;
#define EWALD_F 1.12837917
#define EWALD_P 0.3275911
#define A1 0.254829592
#define A2 -0.284496736
#define A3 1.421413741
#define A4 -1.453152027
#define A5 1.061405429
/* ---------------------------------------------------------------------- */
PairLJCoulOMP::PairLJCoulOMP(LAMMPS *lmp) :
PairLJCoul(lmp), ThrOMP(lmp, THR_PAIR)
{
respa_enable = 0;
}
/* ---------------------------------------------------------------------- */
void PairLJCoulOMP::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 PairLJCoulOMP::eval(int iifrom, int iito, ThrData * const thr)
{
double evdwl,ecoul,fpair;
evdwl = ecoul = 0.0;
const double * const * const x = atom->x;
double * const * const f = thr->get_f();
const double * const q = atom->q;
const int * const type = atom->type;
const int nlocal = atom->nlocal;
const double * const special_coul = force->special_coul;
const double * const special_lj = force->special_lj;
const double qqrd2e = force->qqrd2e;
const double *x0 = x[0];
double *f0 = f[0], *fi = f0;
int *ilist = list->ilist;
// loop over neighbors of my atoms
int i, ii, j, order1 = ewald_order&(1<<1), order6 = ewald_order&(1<<6);
int *jneigh, *jneighn, typei, typej, ni;
double qi, qri, *cutsqi, *cut_ljsqi, *lj1i, *lj2i, *lj3i, *lj4i, *offseti;
double rsq, r2inv, force_coul, force_lj;
double g2 = g_ewald*g_ewald, g6 = g2*g2*g2, g8 = g6*g2;
vector xi, d;
for (ii = iifrom; ii < iito; ++ii) { // loop over my atoms
i = ilist[ii]; fi = f0+3*i;
if (order1) qri = (qi = q[i])*qqrd2e; // initialize constants
offseti = offset[typei = type[i]];
lj1i = lj1[typei]; lj2i = lj2[typei]; lj3i = lj3[typei]; lj4i = lj4[typei];
cutsqi = cutsq[typei]; cut_ljsqi = cut_ljsq[typei];
memcpy(xi, x0+(i+(i<<1)), sizeof(vector));
jneighn = (jneigh = list->firstneigh[i])+list->numneigh[i];
for (; jneigh<jneighn; ++jneigh) { // loop over neighbors
j = *jneigh;
ni = sbmask(j);
j &= NEIGHMASK;
{ register const double *xj = x0+(j+(j<<1));
d[0] = xi[0] - xj[0]; // pair vector
d[1] = xi[1] - xj[1];
d[2] = xi[2] - xj[2]; }
if ((rsq = vec_dot(d, d)) >= cutsqi[typej = type[j]]) continue;
r2inv = 1.0/rsq;
if (order1 && (rsq < cut_coulsq)) { // coulombic
if (!ncoultablebits || rsq <= tabinnersq) { // series real space
register double r = sqrt(rsq), x = g_ewald*r;
register double s = qri*q[j], t = 1.0/(1.0+EWALD_P*x);
if (ni == 0) {
s *= g_ewald*exp(-x*x);
force_coul = (t *= ((((t*A5+A4)*t+A3)*t+A2)*t+A1)*s/x)+EWALD_F*s;
if (EFLAG) ecoul = t;
}
else { // special case
r = s*(1.0-special_coul[ni])/r; s *= g_ewald*exp(-x*x);
force_coul = (t *= ((((t*A5+A4)*t+A3)*t+A2)*t+A1)*s/x)+EWALD_F*s-r;
if (EFLAG) ecoul = t-r;
}
} // table real space
else {
register union_int_float_t t;
t.f = rsq;
register const int k = (t.i & ncoulmask)>>ncoulshiftbits;
register double f = (rsq-rtable[k])*drtable[k], qiqj = qi*q[j];
if (ni == 0) {
force_coul = qiqj*(ftable[k]+f*dftable[k]);
if (EFLAG) ecoul = qiqj*(etable[k]+f*detable[k]);
}
else { // special case
t.f = (1.0-special_coul[ni])*(ctable[k]+f*dctable[k]);
force_coul = qiqj*(ftable[k]+f*dftable[k]-t.f);
if (EFLAG) ecoul = qiqj*(etable[k]+f*detable[k]-t.f);
}
}
}
else force_coul = ecoul = 0.0;
if (rsq < cut_ljsqi[typej]) { // lj
if (order6) { // long-range lj
register double rn = r2inv*r2inv*r2inv;
register double x2 = g2*rsq, a2 = 1.0/x2;
x2 = a2*exp(-x2)*lj4i[typej];
if (ni == 0) {
force_lj =
(rn*=rn)*lj1i[typej]-g8*(((6.0*a2+6.0)*a2+3.0)*a2+1.0)*x2*rsq;
if (EFLAG)
evdwl = rn*lj3i[typej]-g6*((a2+1.0)*a2+0.5)*x2;
}
else { // special case
register double f = special_lj[ni], t = rn*(1.0-f);
force_lj = f*(rn *= rn)*lj1i[typej]-
g8*(((6.0*a2+6.0)*a2+3.0)*a2+1.0)*x2*rsq+t*lj2i[typej];
if (EFLAG)
evdwl = f*rn*lj3i[typej]-g6*((a2+1.0)*a2+0.5)*x2+t*lj4i[typej];
}
}
else { // cut lj
register double rn = r2inv*r2inv*r2inv;
if (ni == 0) {
force_lj = rn*(rn*lj1i[typej]-lj2i[typej]);
if (EFLAG) evdwl = rn*(rn*lj3i[typej]-lj4i[typej])-offseti[typej];
}
else { // special case
register double f = special_lj[ni];
force_lj = f*rn*(rn*lj1i[typej]-lj2i[typej]);
if (EFLAG)
evdwl = f * (rn*(rn*lj3i[typej]-lj4i[typej])-offseti[typej]);
}
}
}
else force_lj = evdwl = 0.0;
fpair = (force_coul+force_lj)*r2inv;
if (NEWTON_PAIR || j < nlocal) {
register double *fj = f0+(j+(j<<1)), f;
fi[0] += f = d[0]*fpair; fj[0] -= f;
fi[1] += f = d[1]*fpair; fj[1] -= f;
fi[2] += f = d[2]*fpair; fj[2] -= f;
}
else {
fi[0] += d[0]*fpair;
fi[1] += d[1]*fpair;
fi[2] += d[2]*fpair;
}
if (EVFLAG) ev_tally_thr(this,i,j,nlocal,NEWTON_PAIR,
evdwl,ecoul,fpair,d[0],d[1],d[2],thr);
}
}
}
/* ---------------------------------------------------------------------- */
double PairLJCoulOMP::memory_usage()
{
double bytes = memory_usage_thr();
bytes += PairLJCoul::memory_usage();
return bytes;
}

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