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pair_coul_long_omp.cpp
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Tue, May 28, 16:08

pair_coul_long_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_coul_long_omp.h"
#include "atom.h"
#include "comm.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
/* ---------------------------------------------------------------------- */
PairCoulLongOMP::PairCoulLongOMP(LAMMPS *lmp) :
PairCoulLong(lmp), ThrOMP(lmp, PAIR)
{
respa_enable = 0;
}
/* ---------------------------------------------------------------------- */
void PairCoulLongOMP::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 PairCoulLongOMP::eval(double **f, int iifrom, int iito, int tid)
{
int i,j,ii,jj,jnum,itable,itype,jtype;
double qtmp,xtmp,ytmp,ztmp,delx,dely,delz,ecoul,fpair;
double fraction,table;
double r,r2inv,rsq,forcecoul,factor_coul;
double grij,expm2,prefactor,t,erfc;
int *ilist,*jlist,*numneigh,**firstneigh;
ecoul = 0.0;
double **x = atom->x;
double *q = atom->q;
int *type = atom->type;
int nlocal = atom->nlocal;
double *special_coul = force->special_coul;
double qqrd2e = force->qqrd2e;
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];
qtmp = q[i];
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_coul = special_coul[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 < cut_coulsq) {
r2inv = 1.0/rsq;
if (!ncoultablebits || rsq <= tabinnersq) {
r = sqrt(rsq);
grij = g_ewald * r;
expm2 = exp(-grij*grij);
t = 1.0 / (1.0 + EWALD_P*grij);
erfc = t * (A1+t*(A2+t*(A3+t*(A4+t*A5)))) * expm2;
prefactor = qqrd2e * scale[itype][jtype] * qtmp*q[j]/r;
forcecoul = prefactor * (erfc + EWALD_F*grij*expm2);
if (factor_coul < 1.0) forcecoul -= (1.0-factor_coul)*prefactor;
} else {
union_int_float_t rsq_lookup;
rsq_lookup.f = rsq;
itable = rsq_lookup.i & ncoulmask;
itable >>= ncoulshiftbits;
fraction = (rsq_lookup.f - rtable[itable]) * drtable[itable];
table = ftable[itable] + fraction*dftable[itable];
forcecoul = scale[itype][jtype] * qtmp*q[j] * table;
if (factor_coul < 1.0) {
table = ctable[itable] + fraction*dctable[itable];
prefactor = scale[itype][jtype] * qtmp*q[j] * table;
forcecoul -= (1.0-factor_coul)*prefactor;
}
}
fpair = forcecoul * r2inv;
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) {
if (!ncoultablebits || rsq <= tabinnersq)
ecoul = prefactor*erfc;
else {
table = etable[itable] + fraction*detable[itable];
ecoul = scale[itype][jtype] * qtmp*q[j] * table;
}
if (factor_coul < 1.0) ecoul -= (1.0-factor_coul)*prefactor;
}
if (EVFLAG) ev_tally_thr(this, i,j,nlocal,NEWTON_PAIR,
0.0,ecoul,fpair,delx,dely,delz,tid);
}
}
f[i][0] += fxtmp;
f[i][1] += fytmp;
f[i][2] += fztmp;
}
}
/* ---------------------------------------------------------------------- */
double PairCoulLongOMP::memory_usage()
{
double bytes = memory_usage_thr();
bytes += PairCoulLong::memory_usage();
return bytes;
}

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