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lammps/src/USER-OMP/angle_cosine_shift_exp_omp.cpp
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angle_cosine_shift_exp_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.
------------------------------------------------------------------------- */
/* ----------------------------------------------------------------------
Contributing author: Axel Kohlmeyer (Temple U)
------------------------------------------------------------------------- */
#include "angle_cosine_shift_exp_omp.h"
#include "atom.h"
#include "comm.h"
#include "force.h"
#include "neighbor.h"
#include "domain.h"
#include "math_const.h"
#include <math.h>
#include "suffix.h"
using namespace LAMMPS_NS;
using namespace MathConst;
#define SMALL 0.001
/* ---------------------------------------------------------------------- */
AngleCosineShiftExpOMP::AngleCosineShiftExpOMP(class LAMMPS *lmp)
: AngleCosineShiftExp(lmp), ThrOMP(lmp,THR_ANGLE)
{
suffix_flag |= Suffix::OMP;
}
/* ---------------------------------------------------------------------- */
void AngleCosineShiftExpOMP::compute(int eflag, int vflag)
{
if (eflag || vflag) {
ev_setup(eflag,vflag);
} else evflag = 0;
const int nall = atom->nlocal + atom->nghost;
const int nthreads = comm->nthreads;
const int inum = neighbor->nanglelist;
#if defined(_OPENMP)
#pragma omp parallel default(none) shared(eflag,vflag)
#endif
{
int ifrom, ito, tid;
loop_setup_thr(ifrom, ito, tid, inum, nthreads);
ThrData *thr = fix->get_thr(tid);
ev_setup_thr(eflag, vflag, nall, eatom, vatom, thr);
if (evflag) {
if (eflag) {
if (force->newton_bond) eval<1,1,1>(ifrom, ito, thr);
else eval<1,1,0>(ifrom, ito, thr);
} else {
if (force->newton_bond) eval<1,0,1>(ifrom, ito, thr);
else eval<1,0,0>(ifrom, ito, thr);
}
} else {
if (force->newton_bond) eval<0,0,1>(ifrom, ito, thr);
else eval<0,0,0>(ifrom, ito, thr);
}
reduce_thr(this, eflag, vflag, thr);
} // end of omp parallel region
}
template <int EVFLAG, int EFLAG, int NEWTON_BOND>
void AngleCosineShiftExpOMP::eval(int nfrom, int nto, ThrData * const thr)
{
int i1,i2,i3,n,type;
double delx1,dely1,delz1,delx2,dely2,delz2;
double eangle,f1[3],f3[3],ff;
double rsq1,rsq2,r1,r2,c,s,a11,a12,a22;
double exp2,aa,uumin,cccpsss,cssmscc;
const double * const * const x = atom->x;
double * const * const f = thr->get_f();
const int * const * const anglelist = neighbor->anglelist;
const int nlocal = atom->nlocal;
for (n = nfrom; n < nto; n++) {
i1 = anglelist[n][0];
i2 = anglelist[n][1];
i3 = anglelist[n][2];
type = anglelist[n][3];
// 1st bond
delx1 = x[i1][0] - x[i2][0];
dely1 = x[i1][1] - x[i2][1];
delz1 = x[i1][2] - x[i2][2];
domain->minimum_image(delx1,dely1,delz1);
rsq1 = delx1*delx1 + dely1*dely1 + delz1*delz1;
r1 = sqrt(rsq1);
// 2nd bond
delx2 = x[i3][0] - x[i2][0];
dely2 = x[i3][1] - x[i2][1];
delz2 = x[i3][2] - x[i2][2];
domain->minimum_image(delx2,dely2,delz2);
rsq2 = delx2*delx2 + dely2*dely2 + delz2*delz2;
r2 = sqrt(rsq2);
// c = cosine of angle
c = delx1*delx2 + dely1*dely2 + delz1*delz2;
c /= r1*r2;
if (c > 1.0) c = 1.0;
if (c < -1.0) c = -1.0;
// C= sine of angle
s = sqrt(1.0 - c*c);
if (s < SMALL) s = SMALL;
// force & energy
aa=a[type];
uumin=umin[type];
cccpsss = c*cost[type]+s*sint[type];
cssmscc = c*sint[type]-s*cost[type];
if (doExpansion[type])
{ // |a|<0.01 so use expansions relative precision <1e-5
// std::cout << "Using expansion\n";
if (EFLAG) eangle = -0.125*(1+cccpsss)*(4+aa*(cccpsss-1))*uumin;
ff=0.25*uumin*cssmscc*(2+aa*cccpsss)/s;
}
else
{
// std::cout << "Not using expansion\n";
exp2=exp(0.5*aa*(1+cccpsss));
if (EFLAG) eangle = opt1[type]*(1-exp2);
ff=0.5*a[type]*opt1[type]*exp2*cssmscc/s;
}
a11 = ff*c/ rsq1;
a12 = -ff / (r1*r2);
a22 = ff*c/ rsq2;
f1[0] = a11*delx1 + a12*delx2;
f1[1] = a11*dely1 + a12*dely2;
f1[2] = a11*delz1 + a12*delz2;
f3[0] = a22*delx2 + a12*delx1;
f3[1] = a22*dely2 + a12*dely1;
f3[2] = a22*delz2 + a12*delz1;
// apply force to each of 3 atoms
if (NEWTON_BOND || i1 < nlocal) {
f[i1][0] += f1[0];
f[i1][1] += f1[1];
f[i1][2] += f1[2];
}
if (NEWTON_BOND || i2 < nlocal) {
f[i2][0] -= f1[0] + f3[0];
f[i2][1] -= f1[1] + f3[1];
f[i2][2] -= f1[2] + f3[2];
}
if (NEWTON_BOND || i3 < nlocal) {
f[i3][0] += f3[0];
f[i3][1] += f3[1];
f[i3][2] += f3[2];
}
if (EVFLAG) ev_tally_thr(this,i1,i2,i3,nlocal,NEWTON_BOND,eangle,f1,f3,
delx1,dely1,delz1,delx2,dely2,delz2,thr);
}
}
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