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pair_lj_cut_opt.cpp
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Sun, May 26, 15:32

pair_lj_cut_opt.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 authors:
James Fischer, High Performance Technologies, Inc.
David Richie, Stone Ridge Technology
Vincent Natoli, Stone Ridge Technology
------------------------------------------------------------------------- */
#include <stdlib.h>
#include "pair_lj_cut_opt.h"
#include "atom.h"
#include "force.h"
#include "neigh_list.h"
using namespace LAMMPS_NS;
/* ---------------------------------------------------------------------- */
PairLJCutOpt::PairLJCutOpt(LAMMPS *lmp) : PairLJCut(lmp) {}
/* ---------------------------------------------------------------------- */
void PairLJCutOpt::compute(int eflag, int vflag)
{
if (eflag || vflag) ev_setup(eflag,vflag);
else evflag = vflag_fdotr = 0;
if (evflag) {
if (eflag) {
if (force->newton_pair) return eval<1,1,1>();
else return eval<1,1,0>();
} else {
if (force->newton_pair) return eval<1,0,1>();
else return eval<1,0,0>();
}
} else {
if (force->newton_pair) return eval<0,0,1>();
else return eval<0,0,0>();
}
}
/* ---------------------------------------------------------------------- */
template < int EVFLAG, int EFLAG, int NEWTON_PAIR >
void PairLJCutOpt::eval()
{
typedef struct { double x,y,z; } vec3_t;
typedef struct {
double cutsq,lj1,lj2,lj3,lj4,offset;
double _pad[2];
} fast_alpha_t;
int i,j,ii,jj,inum,jnum,itype,jtype,sbindex;
double factor_lj;
double evdwl = 0.0;
double** _noalias x = atom->x;
double** _noalias f = atom->f;
int* _noalias type = atom->type;
int nlocal = atom->nlocal;
double* _noalias special_lj = force->special_lj;
inum = list->inum;
int* _noalias ilist = list->ilist;
int** _noalias firstneigh = list->firstneigh;
int* _noalias numneigh = list->numneigh;
vec3_t* _noalias xx = (vec3_t*)x[0];
vec3_t* _noalias ff = (vec3_t*)f[0];
int ntypes = atom->ntypes;
int ntypes2 = ntypes*ntypes;
fast_alpha_t* _noalias fast_alpha =
(fast_alpha_t*) malloc(ntypes2*sizeof(fast_alpha_t));
for (i = 0; i < ntypes; i++) for (j = 0; j < ntypes; j++) {
fast_alpha_t& a = fast_alpha[i*ntypes+j];
a.cutsq = cutsq[i+1][j+1];
a.lj1 = lj1[i+1][j+1];
a.lj2 = lj2[i+1][j+1];
a.lj3 = lj3[i+1][j+1];
a.lj4 = lj4[i+1][j+1];
a.offset = offset[i+1][j+1];
}
fast_alpha_t* _noalias tabsix = fast_alpha;
// loop over neighbors of my atoms
for (ii = 0; ii < inum; ii++) {
i = ilist[ii];
double xtmp = xx[i].x;
double ytmp = xx[i].y;
double ztmp = xx[i].z;
itype = type[i] - 1;
int* _noalias jlist = firstneigh[i];
jnum = numneigh[i];
double tmpfx = 0.0;
double tmpfy = 0.0;
double tmpfz = 0.0;
fast_alpha_t* _noalias tabsixi = (fast_alpha_t*)&tabsix[itype*ntypes];
for (jj = 0; jj < jnum; jj++) {
j = jlist[jj];
sbindex = sbmask(j);
if (sbindex == 0) {
double delx = xtmp - xx[j].x;
double dely = ytmp - xx[j].y;
double delz = ztmp - xx[j].z;
double rsq = delx*delx + dely*dely + delz*delz;
jtype = type[j] - 1;
fast_alpha_t& a = tabsixi[jtype];
if (rsq < a.cutsq) {
double r2inv = 1.0/rsq;
double r6inv = r2inv*r2inv*r2inv;
double forcelj = r6inv * (a.lj1*r6inv - a.lj2);
double fpair = forcelj*r2inv;
tmpfx += delx*fpair;
tmpfy += dely*fpair;
tmpfz += delz*fpair;
if (NEWTON_PAIR || j < nlocal) {
ff[j].x -= delx*fpair;
ff[j].y -= dely*fpair;
ff[j].z -= delz*fpair;
}
if (EFLAG) evdwl = r6inv*(a.lj3*r6inv-a.lj4) - a.offset;
if (EVFLAG)
ev_tally(i,j,nlocal,NEWTON_PAIR,
evdwl,0.0,fpair,delx,dely,delz);
}
} else {
factor_lj = special_lj[sbindex];
j &= NEIGHMASK;
double delx = xtmp - xx[j].x;
double dely = ytmp - xx[j].y;
double delz = ztmp - xx[j].z;
double rsq = delx*delx + dely*dely + delz*delz;
int jtype1 = type[j];
jtype = jtype1 - 1;
fast_alpha_t& a = tabsixi[jtype];
if (rsq < a.cutsq) {
double r2inv = 1.0/rsq;
double r6inv = r2inv*r2inv*r2inv;
fast_alpha_t& a = tabsixi[jtype];
double forcelj = r6inv * (a.lj1*r6inv - a.lj2);
double fpair = factor_lj*forcelj*r2inv;
tmpfx += delx*fpair;
tmpfy += dely*fpair;
tmpfz += delz*fpair;
if (NEWTON_PAIR || j < nlocal) {
ff[j].x -= delx*fpair;
ff[j].y -= dely*fpair;
ff[j].z -= delz*fpair;
}
if (EFLAG) {
evdwl = r6inv*(a.lj3*r6inv-a.lj4) - a.offset;
evdwl *= factor_lj;
}
if (EVFLAG) ev_tally(i,j,nlocal,NEWTON_PAIR,
evdwl,0.0,fpair,delx,dely,delz);
}
}
}
ff[i].x += tmpfx;
ff[i].y += tmpfy;
ff[i].z += tmpfz;
}
free(fast_alpha); fast_alpha = 0;
if (vflag_fdotr) virial_fdotr_compute();
}

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