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pair_dpd_tstat_omp.cpp
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Sun, Apr 6, 01:56

pair_dpd_tstat_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
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.
------------------------------------------------------------------------- */
#include "math.h"
#include "pair_dpd_tstat_omp.h"
#include "atom.h"
#include "update.h"
#include "force.h"
#include "neigh_list.h"
#include "comm.h"
#include "random_mars.h"
#include "error.h"
using namespace LAMMPS_NS;
#define MIN(a,b) ((a) < (b) ? (a) : (b))
#define MAX(a,b) ((a) > (b) ? (a) : (b))
#define EPSILON 1.0e-20
/* ---------------------------------------------------------------------- */
PairDPDTstatOMP::PairDPDTstatOMP(LAMMPS *lmp) : PairDPDOMP(lmp)
{
single_enable = 0;
}
/* ---------------------------------------------------------------------- */
void PairDPDTstatOMP::compute(int eflag, int vflag)
{
int i,j;
if (eflag || vflag) {
ev_setup(eflag,vflag);
ev_setup_thr(eflag,vflag);
} else evflag = vflag_fdotr = 0;
// adjust sigma if target T is changing
if (t_start != t_stop) {
double delta = update->ntimestep - update->beginstep;
delta /= update->endstep - update->beginstep;
temperature = t_start + delta * (t_stop-t_start);
double boltz = force->boltz;
for (i = 1; i <= atom->ntypes; i++)
for (j = i+1; j <= atom->ntypes; j++)
sigma[i][j] = sigma[j][i] = sqrt(2.0*boltz*temperature*gamma[i][j]);
}
if (evflag) {
if (eflag) {
if (force->newton_pair) return eval_tstat<1,1,1>();
else return eval_tstat<1,1,0>();
} else {
if (force->newton_pair) return eval_tstat<1,0,1>();
else return eval_tstat<1,0,0>();
}
} else {
if (force->newton_pair) return eval_tstat<0,0,1>();
else return eval_tstat<0,0,0>();
}
}
template <int EVFLAG, int EFLAG, int NEWTON_PAIR>
void PairDPDTstatOMP::eval_tstat()
{
#if defined(_OPENMP)
#pragma omp parallel default(shared)
#endif
{
int i,j,ii,jj,inum,jnum,itype,jtype,tid;
double xtmp,ytmp,ztmp,delx,dely,delz,fpair;
double vxtmp,vytmp,vztmp,delvx,delvy,delvz;
double rsq,r,rinv,dot,wd,randnum,factor_dpd;
int *ilist,*jlist,*numneigh,**firstneigh;
int nlocal = atom->nlocal;
int nall = nlocal + atom->nghost;
int nthreads = comm->nthreads;
double **x = atom->x;
double **v = atom->v;
int *type = atom->type;
double *special_lj = force->special_lj;
double dtinvsqrt = 1.0/sqrt(update->dt);
inum = list->inum;
ilist = list->ilist;
numneigh = list->numneigh;
firstneigh = list->firstneigh;
// loop over neighbors of my atoms
int iifrom, iito;
double **f = loop_setup_thr(atom->f,iifrom,iito,tid,inum,nall,nthreads);
RanMars *rng = random[tid];
for (ii = iifrom; ii < iito; ++ii) {
i = ilist[ii];
xtmp = x[i][0];
ytmp = x[i][1];
ztmp = x[i][2];
vxtmp = v[i][0];
vytmp = v[i][1];
vztmp = v[i][2];
itype = type[i];
jlist = firstneigh[i];
jnum = numneigh[i];
for (jj = 0; jj < jnum; jj++) {
j = jlist[jj];
if (j < nall) factor_dpd = 1.0;
else {
factor_dpd = special_lj[j/nall];
j %= nall;
}
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 < cutsq[itype][jtype]) && (rsq > EPSILON)) { // r can be 0.0 in DPD systems
r = sqrt(rsq);
rinv = 1.0/r;
delvx = vxtmp - v[j][0];
delvy = vytmp - v[j][1];
delvz = vztmp - v[j][2];
dot = delx*delvx + dely*delvy + delz*delvz;
wd = 1.0 - r/cut[itype][jtype];
randnum = rng->gaussian();
// drag force = -gamma * wd^2 * (delx dot delv) / r
// random force = sigma * wd * rnd * dtinvsqrt;
fpair = gamma[itype][jtype]*wd*wd*dot*rinv;
fpair += sigma[itype][jtype]*wd*randnum*dtinvsqrt;
fpair *= factor_dpd*rinv;
f[i][0] += delx*fpair;
f[i][1] += dely*fpair;
f[i][2] += delz*fpair;
if (NEWTON_PAIR || j < nlocal) {
f[j][0] -= delx*fpair;
f[j][1] -= dely*fpair;
f[j][2] -= delz*fpair;
}
if (EVFLAG) ev_tally(i,j,nlocal,NEWTON_PAIR,
0.0,0.0,fpair,delx,dely,delz);
}
}
}
// reduce per thread forces into global force array.
force_reduce_thr(atom->f,nall,nthreads,tid);
}
ev_reduce_thr();
if (vflag_fdotr) virial_compute();
}
/* ----------------------------------------------------------------------
global settings
------------------------------------------------------------------------- */
void PairDPDTstatOMP::settings(int narg, char **arg)
{
if (narg != 4) error->all("Illegal pair_style command");
t_start = force->numeric(arg[0]);
t_stop = force->numeric(arg[1]);
cut_global = force->numeric(arg[2]);
seed = force->inumeric(arg[3]);
temperature = t_start;
// initialize Marsaglia RNG with processor-unique seed
if (seed <= 0) error->all("Illegal pair_style command");
// we need to set up individual RNGs for each thread.
int nthreads = comm->nthreads;
int tid;
if (random) {
for (tid=0; tid < nthreads; ++tid)
delete random[tid];
delete[] random;
}
random = new RanMars*[nthreads];
for (tid=0; tid < nthreads; ++tid)
random[tid] = new RanMars(lmp,seed + nthreads*comm->me + tid);
// reset cutoffs that have been explicitly set
if (allocated) {
int i,j;
for (i = 1; i <= atom->ntypes; i++)
for (j = i+1; j <= atom->ntypes; j++)
if (setflag[i][j]) cut[i][j] = cut_global;
}
}
/* ----------------------------------------------------------------------
set coeffs for one or more type pairs
------------------------------------------------------------------------- */
void PairDPDTstatOMP::coeff(int narg, char **arg)
{
if (narg < 3 || narg > 4) error->all("Incorrect args for pair coefficients");
if (!allocated) allocate();
int ilo,ihi,jlo,jhi;
force->bounds(arg[0],atom->ntypes,ilo,ihi);
force->bounds(arg[1],atom->ntypes,jlo,jhi);
double a0_one = 0.0;
double gamma_one = force->numeric(arg[2]);
double cut_one = cut_global;
if (narg == 4) cut_one = force->numeric(arg[3]);
int count = 0;
for (int i = ilo; i <= ihi; i++) {
for (int j = MAX(jlo,i); j <= jhi; j++) {
a0[i][j] = a0_one;
gamma[i][j] = gamma_one;
cut[i][j] = cut_one;
setflag[i][j] = 1;
count++;
}
}
if (count == 0) error->all("Incorrect args for pair coefficients");
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void PairDPDTstatOMP::write_restart_settings(FILE *fp)
{
fwrite(&t_start,sizeof(double),1,fp);
fwrite(&t_stop,sizeof(double),1,fp);
fwrite(&cut_global,sizeof(double),1,fp);
fwrite(&seed,sizeof(int),1,fp);
fwrite(&mix_flag,sizeof(int),1,fp);
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void PairDPDTstatOMP::read_restart_settings(FILE *fp)
{
if (comm->me == 0) {
fread(&t_start,sizeof(double),1,fp);
fread(&t_stop,sizeof(double),1,fp);
fread(&cut_global,sizeof(double),1,fp);
fread(&seed,sizeof(int),1,fp);
fread(&mix_flag,sizeof(int),1,fp);
}
MPI_Bcast(&t_start,1,MPI_DOUBLE,0,world);
MPI_Bcast(&t_stop,1,MPI_DOUBLE,0,world);
MPI_Bcast(&cut_global,1,MPI_DOUBLE,0,world);
MPI_Bcast(&seed,1,MPI_INT,0,world);
MPI_Bcast(&mix_flag,1,MPI_INT,0,world);
// initialize Marsaglia RNG with processor-unique seed
// same seed that pair_style command initially specified
// we need to set up individual RNGs for each thread.
int nthreads = comm->nthreads;
int tid;
if (random) {
for (tid=0; tid < nthreads; ++tid)
delete random[tid];
delete[] random;
}
random = new RanMars*[nthreads];
for (tid=0; tid < nthreads; ++tid)
random[tid] = new RanMars(lmp,seed + nthreads*comm->me + tid);
}

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