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pair_coul_dsf_gpu.cpp
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Mon, Nov 11, 18:21

pair_coul_dsf_gpu.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 author: Trung Dac Nguyen (ORNL)
------------------------------------------------------------------------- */
#include "math.h"
#include "stdio.h"
#include "stdlib.h"
#include "pair_coul_dsf_gpu.h"
#include "atom.h"
#include "atom_vec.h"
#include "comm.h"
#include "force.h"
#include "neighbor.h"
#include "neigh_list.h"
#include "integrate.h"
#include "memory.h"
#include "error.h"
#include "neigh_request.h"
#include "universe.h"
#include "update.h"
#include "domain.h"
#include "string.h"
#include "gpu_extra.h"
#define MY_PIS 1.77245385090551602729
#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
using namespace LAMMPS_NS;
// External functions from cuda library for atom decomposition
int cdsf_gpu_init(const int ntypes, const int nlocal, const int nall,
const int max_nbors, const int maxspecial,
const double cell_size, int &gpu_mode, FILE *screen,
const double host_cut_coulsq,
double *host_special_coul, const double qqrd2e,
const double e_shift, const double f_shift,
const double alpha);
void cdsf_gpu_clear();
int ** cdsf_gpu_compute_n(const int ago, const int inum,
const int nall, double **host_x, int *host_type,
double *sublo, double *subhi, tagint *tag, int **nspecial,
tagint **special, const bool eflag, const bool vflag,
const bool eatom, const bool vatom, int &host_start,
int **ilist, int **jnum, const double cpu_time,
bool &success, double *host_q, double *boxlo,
double *prd);
void cdsf_gpu_compute(const int ago, const int inum,
const int nall, double **host_x, int *host_type,
int *ilist, int *numj, int **firstneigh,
const bool eflag, const bool vflag, const bool eatom,
const bool vatom, int &host_start, const double cpu_time,
bool &success, double *host_q, const int nlocal,
double *boxlo, double *prd);
double cdsf_gpu_bytes();
/* ---------------------------------------------------------------------- */
PairCoulDSFGPU::PairCoulDSFGPU(LAMMPS *lmp) : PairCoulDSF(lmp),
gpu_mode(GPU_FORCE)
{
respa_enable = 0;
reinitflag = 0;
cpu_time = 0.0;
GPU_EXTRA::gpu_ready(lmp->modify, lmp->error);
}
/* ----------------------------------------------------------------------
free all arrays
------------------------------------------------------------------------- */
PairCoulDSFGPU::~PairCoulDSFGPU()
{
cdsf_gpu_clear();
}
/* ---------------------------------------------------------------------- */
void PairCoulDSFGPU::compute(int eflag, int vflag)
{
if (eflag || vflag) ev_setup(eflag,vflag);
else evflag = vflag_fdotr = 0;
int nall = atom->nlocal + atom->nghost;
int inum, host_start;
bool success = true;
int *ilist, *numneigh, **firstneigh;
if (gpu_mode != GPU_FORCE) {
inum = atom->nlocal;
firstneigh = cdsf_gpu_compute_n(neighbor->ago, inum, nall, atom->x,
atom->type, domain->sublo, domain->subhi,
atom->tag, atom->nspecial, atom->special,
eflag, vflag, eflag_atom, vflag_atom,
host_start, &ilist, &numneigh, cpu_time,
success, atom->q, domain->boxlo,
domain->prd);
} else {
inum = list->inum;
ilist = list->ilist;
numneigh = list->numneigh;
firstneigh = list->firstneigh;
cdsf_gpu_compute(neighbor->ago, inum, nall, atom->x, atom->type,
ilist, numneigh, firstneigh, eflag, vflag, eflag_atom,
vflag_atom, host_start, cpu_time, success, atom->q,
atom->nlocal, domain->boxlo, domain->prd);
}
if (!success)
error->one(FLERR,"Insufficient memory on accelerator");
if (host_start<inum) {
cpu_time = MPI_Wtime();
cpu_compute(host_start, inum, eflag, vflag, ilist, numneigh, firstneigh);
cpu_time = MPI_Wtime() - cpu_time;
}
}
/* ----------------------------------------------------------------------
init specific to this pair style
------------------------------------------------------------------------- */
void PairCoulDSFGPU::init_style()
{
if (!atom->q_flag)
error->all(FLERR,"Pair style coul/dsf/gpu requires atom attribute q");
if (force->newton_pair)
error->all(FLERR,"Cannot use newton pair with coul/dsf/gpu pair style");
// Repeat cutsq calculation because done after call to init_style
double maxcut = -1.0;
double cut;
for (int i = 1; i <= atom->ntypes; i++) {
for (int j = i; j <= atom->ntypes; j++) {
if (setflag[i][j] != 0 || (setflag[i][i] != 0 && setflag[j][j] != 0)) {
cut = init_one(i,j);
cut *= cut;
if (cut > maxcut)
maxcut = cut;
cutsq[i][j] = cutsq[j][i] = cut;
} else
cutsq[i][j] = cutsq[j][i] = 0.0;
}
}
double cell_size = sqrt(maxcut) + neighbor->skin;
cut_coulsq = cut_coul * cut_coul;
double erfcc = erfc(alpha*cut_coul);
double erfcd = exp(-alpha*alpha*cut_coul*cut_coul);
f_shift = -(erfcc/cut_coulsq + 2.0/MY_PIS*alpha*erfcd/cut_coul);
e_shift = erfcc/cut_coul - f_shift*cut_coul;
int maxspecial=0;
if (atom->molecular)
maxspecial=atom->maxspecial;
int success = cdsf_gpu_init(atom->ntypes+1, atom->nlocal,
atom->nlocal+atom->nghost, 300, maxspecial,
cell_size, gpu_mode, screen, cut_coulsq,
force->special_coul, force->qqrd2e, e_shift,
f_shift, alpha);
GPU_EXTRA::check_flag(success,error,world);
if (gpu_mode == GPU_FORCE) {
int irequest = neighbor->request(this);
neighbor->requests[irequest]->half = 0;
neighbor->requests[irequest]->full = 1;
}
}
/* ---------------------------------------------------------------------- */
double PairCoulDSFGPU::memory_usage()
{
double bytes = Pair::memory_usage();
return bytes + cdsf_gpu_bytes();
}
/* ---------------------------------------------------------------------- */
void PairCoulDSFGPU::cpu_compute(int start, int inum, int eflag, int vflag,
int *ilist, int *numneigh,
int **firstneigh)
{
int i,j,ii,jj,jnum;
double qtmp,xtmp,ytmp,ztmp,delx,dely,delz,ecoul,fpair;
double r,rsq,r2inv,forcecoul,factor_coul;
double prefactor,erfcc,erfcd,e_self,t;
int *jlist;
ecoul = 0.0;
double **x = atom->x;
double **f = atom->f;
double *q = atom->q;
int nlocal = atom->nlocal;
double *special_coul = force->special_coul;
double qqrd2e = force->qqrd2e;
// loop over neighbors of my atoms
for (ii = start; ii < inum; ii++) {
i = ilist[ii];
qtmp = q[i];
xtmp = x[i][0];
ytmp = x[i][1];
ztmp = x[i][2];
jlist = firstneigh[i];
jnum = numneigh[i];
if (evflag) {
e_self = -(e_shift/2.0 + alpha/MY_PIS) * qtmp*qtmp*qqrd2e;
ev_tally(i,i,nlocal,0,0.0,e_self,0.0,0.0,0.0,0.0);
}
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;
if (rsq < cut_coulsq) {
r2inv = 1.0/rsq;
r = sqrt(rsq);
prefactor = factor_coul * qqrd2e*qtmp*q[j]/r;
erfcd = exp(-alpha*alpha*r*r);
t = 1.0 / (1.0 + EWALD_P*alpha*r);
erfcc = t * (A1+t*(A2+t*(A3+t*(A4+t*A5)))) * erfcd;
forcecoul = prefactor * (erfcc/r + 2.0*alpha/MY_PIS * erfcd +
r*f_shift) * r;
fpair = forcecoul * r2inv;
f[i][0] += delx*fpair;
f[i][1] += dely*fpair;
f[i][2] += delz*fpair;
if (eflag) {
if (rsq < cut_coulsq) {
ecoul = prefactor * (erfcc - r*e_shift - rsq*f_shift);
} else ecoul = 0.0;
}
if (evflag) ev_tally_full(i,0.0,ecoul,fpair,delx,dely,delz);
}
}
}
}

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