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pair_morse_opt.h
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pair_morse_opt.h
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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 Natol, Stone Ridge Technology
------------------------------------------------------------------------- */
#ifndef PAIR_MORSE_OPT_H
#define PAIR_MORSE_OPT_H
#include "math.h"
#include "stdio.h"
#include "stdlib.h"
#include "pair_morse.h"
#include "atom.h"
#include "comm.h"
#include "force.h"
#include "update.h"
#include "memory.h"
#include "neighbor.h"
#include "error.h"
namespace LAMMPS_NS {
class PairMorseOpt : public PairMorse {
public:
PairMorseOpt(class LAMMPS *);
void compute(int, int);
private:
template < int EFLAG, int VFLAG, int NEWTON_PAIR > void eval();
};
template < int EFLAG, int VFLAG, int NEWTON_PAIR >
void PairMorseOpt::eval()
{
typedef struct { double x,y,z; } vec3_t;
typedef struct {
double cutsq,r0,alpha,morse1,d0,offset;
double _pad[2];
} fast_alpha_t;
double** __restrict__ f;
eng_vdwl = 0.0;
if (VFLAG) for (int i = 0; i < 6; i++) virial[i] = 0.0;
if (VFLAG == 2) f = update->f_pair;
else f = atom->f;
double** __restrict__ x = atom->x;
int* __restrict__ type = atom->type;
int nlocal = atom->nlocal;
int nall = atom->nlocal + atom->nghost;
double* __restrict__ special_lj = force->special_lj;
int** __restrict__ firstneigh = neighbor->firstneigh;
int* __restrict__ num = neighbor->numneigh;
vec3_t* __restrict__ xx = (vec3_t*)x[0];
vec3_t* __restrict__ ff = (vec3_t*)f[0];
int ntypes = atom->ntypes;
int ntypes2 = ntypes*ntypes;
fast_alpha_t* __restrict__ fast_alpha =
(fast_alpha_t*) malloc(ntypes2*sizeof(fast_alpha_t));
for( int i = 0; i < ntypes; i++) for( int j = 0; j < ntypes; j++) {
fast_alpha_t& a = fast_alpha[i*ntypes+j];
a.cutsq = cutsq[i+1][j+1];
a.r0 = r0[i+1][j+1];
a.alpha = alpha[i+1][j+1];
a.morse1 = morse1[i+1][j+1];
a.d0 = d0[i+1][j+1];
a.offset = offset[i+1][j+1];
}
fast_alpha_t* __restrict__ tabsix = fast_alpha;
// loop over neighbors of my atoms
for (int i = 0; i < nlocal; i++) {
double xtmp = xx[i].x;
double ytmp = xx[i].y;
double ztmp = xx[i].z;
int itype = type[i] - 1;
int* __restrict__ neighs = firstneigh[i];
int numneigh = num[i];
double tmpfx = 0.0;
double tmpfy = 0.0;
double tmpfz = 0.0;
fast_alpha_t* __restrict__ tabsixi = (fast_alpha_t*)&tabsix[itype*ntypes];
for (int k = 0; k < numneigh; k++) {
int j = neighs[k];
double factor_lj;
if (j < nall) {
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 jtype = type[j] - 1;
fast_alpha_t& a = tabsixi[jtype];
if (rsq < a.cutsq) {
double r = sqrt(rsq);
double dr = r - a.r0;
double dexp = exp(-a.alpha * dr);
double fforce = a.morse1 * (dexp*dexp - dexp) / r;
if (EFLAG) {
double phi = a.d0 * (dexp*dexp - 2.0*dexp) - a.offset;
if (NEWTON_PAIR || j < nlocal) {
eng_vdwl += phi;
} else {
eng_vdwl += 0.5*phi;
}
}
tmpfx += delx*fforce;
tmpfy += dely*fforce;
tmpfz += delz*fforce;
if (NEWTON_PAIR || j < nlocal) {
ff[j].x -= delx*fforce;
ff[j].y -= dely*fforce;
ff[j].z -= delz*fforce;
}
if (VFLAG == 1) {
if (NEWTON_PAIR == 0 && j >= nlocal) fforce *= 0.5;
virial[0] += delx*delx*fforce;
virial[1] += dely*dely*fforce;
virial[2] += delz*delz*fforce;
virial[3] += delx*dely*fforce;
virial[4] += delx*delz*fforce;
virial[5] += dely*delz*fforce;
}
}
} else {
factor_lj = special_lj[j/nall];
j = j % nall;
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 jtype = type[j] - 1;
fast_alpha_t& a = tabsixi[jtype];
if (rsq < a.cutsq) {
double r = sqrt(rsq);
double dr = r - a.r0;
double dexp = exp(-a.alpha * dr);
double fforce = factor_lj * a.morse1 * (dexp*dexp - dexp) / r;
if (EFLAG) {
double phi = a.d0 * (dexp*dexp - 2.0*dexp) - a.offset;
if (NEWTON_PAIR || j < nlocal) {
eng_vdwl += factor_lj*phi;
} else {
eng_vdwl += 0.5*factor_lj*phi;
}
}
tmpfx += delx*fforce;
tmpfy += dely*fforce;
tmpfz += delz*fforce;
if (NEWTON_PAIR || j < nlocal) {
ff[j].x -= delx*fforce;
ff[j].y -= dely*fforce;
ff[j].z -= delz*fforce;
}
if (VFLAG == 1) {
if (NEWTON_PAIR == 0 && j >= nlocal) fforce *= 0.5;
virial[0] += delx*delx*fforce;
virial[1] += dely*dely*fforce;
virial[2] += delz*delz*fforce;
virial[3] += delx*dely*fforce;
virial[4] += delx*delz*fforce;
virial[5] += dely*delz*fforce;
}
}
}
}
ff[i].x += tmpfx;
ff[i].y += tmpfy;
ff[i].z += tmpfz;
}
if (VFLAG == 2) virial_compute();
free(fast_alpha); fast_alpha = 0;
}
}
#endif

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