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dihedral_opls_omp.cpp
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Sun, Nov 10, 14:20

dihedral_opls_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 <math.h>
#include "dihedral_opls_omp.h"
#include "atom.h"
#include "comm.h"
#include "neighbor.h"
#include "domain.h"
#include "force.h"
#include "update.h"
#include "error.h"
#include "suffix.h"
using namespace LAMMPS_NS;
#define TOLERANCE 0.05
#define SMALL 0.001
#define SMALLER 0.00001
/* ---------------------------------------------------------------------- */
DihedralOPLSOMP::DihedralOPLSOMP(class LAMMPS *lmp)
: DihedralOPLS(lmp), ThrOMP(lmp,THR_DIHEDRAL)
{
suffix_flag |= Suffix::OMP;
}
/* ---------------------------------------------------------------------- */
void DihedralOPLSOMP::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->ndihedrallist;
#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);
thr->timer(Timer::START);
ev_setup_thr(eflag, vflag, nall, eatom, vatom, thr);
if (inum > 0) {
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);
}
}
thr->timer(Timer::BOND);
reduce_thr(this, eflag, vflag, thr);
} // end of omp parallel region
}
template <int EVFLAG, int EFLAG, int NEWTON_BOND>
void DihedralOPLSOMP::eval(int nfrom, int nto, ThrData * const thr)
{
int i1,i2,i3,i4,n,type;
double vb1x,vb1y,vb1z,vb2x,vb2y,vb2z,vb3x,vb3y,vb3z,vb2xm,vb2ym,vb2zm;
double edihedral,f1[3],f2[3],f3[3],f4[3];
double sb1,sb2,sb3,rb1,rb3,c0,b1mag2,b1mag,b2mag2;
double b2mag,b3mag2,b3mag,ctmp,r12c1,c1mag,r12c2;
double c2mag,sc1,sc2,s1,s12,c,pd,a,a11,a22;
double a33,a12,a13,a23,sx2,sy2,sz2;
double s2,cx,cy,cz,cmag,dx,phi,si,siinv,sin2;
edihedral = 0.0;
const dbl3_t * _noalias const x = (dbl3_t *) atom->x[0];
dbl3_t * _noalias const f = (dbl3_t *) thr->get_f()[0];
const int5_t * _noalias const dihedrallist = (int5_t *) neighbor->dihedrallist[0];
const int nlocal = atom->nlocal;
for (n = nfrom; n < nto; n++) {
i1 = dihedrallist[n].a;
i2 = dihedrallist[n].b;
i3 = dihedrallist[n].c;
i4 = dihedrallist[n].d;
type = dihedrallist[n].t;
// 1st bond
vb1x = x[i1].x - x[i2].x;
vb1y = x[i1].y - x[i2].y;
vb1z = x[i1].z - x[i2].z;
// 2nd bond
vb2x = x[i3].x - x[i2].x;
vb2y = x[i3].y - x[i2].y;
vb2z = x[i3].z - x[i2].z;
vb2xm = -vb2x;
vb2ym = -vb2y;
vb2zm = -vb2z;
// 3rd bond
vb3x = x[i4].x - x[i3].x;
vb3y = x[i4].y - x[i3].y;
vb3z = x[i4].z - x[i3].z;
// c0 calculation
sb1 = 1.0 / (vb1x*vb1x + vb1y*vb1y + vb1z*vb1z);
sb2 = 1.0 / (vb2x*vb2x + vb2y*vb2y + vb2z*vb2z);
sb3 = 1.0 / (vb3x*vb3x + vb3y*vb3y + vb3z*vb3z);
rb1 = sqrt(sb1);
rb3 = sqrt(sb3);
c0 = (vb1x*vb3x + vb1y*vb3y + vb1z*vb3z) * rb1*rb3;
// 1st and 2nd angle
b1mag2 = vb1x*vb1x + vb1y*vb1y + vb1z*vb1z;
b1mag = sqrt(b1mag2);
b2mag2 = vb2x*vb2x + vb2y*vb2y + vb2z*vb2z;
b2mag = sqrt(b2mag2);
b3mag2 = vb3x*vb3x + vb3y*vb3y + vb3z*vb3z;
b3mag = sqrt(b3mag2);
ctmp = vb1x*vb2x + vb1y*vb2y + vb1z*vb2z;
r12c1 = 1.0 / (b1mag*b2mag);
c1mag = ctmp * r12c1;
ctmp = vb2xm*vb3x + vb2ym*vb3y + vb2zm*vb3z;
r12c2 = 1.0 / (b2mag*b3mag);
c2mag = ctmp * r12c2;
// cos and sin of 2 angles and final c
sin2 = MAX(1.0 - c1mag*c1mag,0.0);
sc1 = sqrt(sin2);
if (sc1 < SMALL) sc1 = SMALL;
sc1 = 1.0/sc1;
sin2 = MAX(1.0 - c2mag*c2mag,0.0);
sc2 = sqrt(sin2);
if (sc2 < SMALL) sc2 = SMALL;
sc2 = 1.0/sc2;
s1 = sc1 * sc1;
s2 = sc2 * sc2;
s12 = sc1 * sc2;
c = (c0 + c1mag*c2mag) * s12;
cx = vb1y*vb2z - vb1z*vb2y;
cy = vb1z*vb2x - vb1x*vb2z;
cz = vb1x*vb2y - vb1y*vb2x;
cmag = sqrt(cx*cx + cy*cy + cz*cz);
dx = (cx*vb3x + cy*vb3y + cz*vb3z)/cmag/b3mag;
// error check
if (c > 1.0 + TOLERANCE || c < (-1.0 - TOLERANCE)) {
int me = comm->me;
if (screen) {
char str[128];
sprintf(str,"Dihedral problem: %d/%d " BIGINT_FORMAT " "
TAGINT_FORMAT " " TAGINT_FORMAT " "
TAGINT_FORMAT " " TAGINT_FORMAT,
me,thr->get_tid(),update->ntimestep,
atom->tag[i1],atom->tag[i2],atom->tag[i3],atom->tag[i4]);
error->warning(FLERR,str,0);
fprintf(screen," 1st atom: %d %g %g %g\n",
me,x[i1].x,x[i1].y,x[i1].z);
fprintf(screen," 2nd atom: %d %g %g %g\n",
me,x[i2].x,x[i2].y,x[i2].z);
fprintf(screen," 3rd atom: %d %g %g %g\n",
me,x[i3].x,x[i3].y,x[i3].z);
fprintf(screen," 4th atom: %d %g %g %g\n",
me,x[i4].x,x[i4].y,x[i4].z);
}
}
if (c > 1.0) c = 1.0;
if (c < -1.0) c = -1.0;
// force & energy
// p = sum (i=1,4) k_i * (1 + (-1)**(i+1)*cos(i*phi) )
// pd = dp/dc
phi = acos(c);
if (dx < 0.0) phi *= -1.0;
si = sin(phi);
if (fabs(si) < SMALLER) si = SMALLER;
siinv = 1.0/si;
pd = k1[type] - 2.0*k2[type]*sin(2.0*phi)*siinv +
3.0*k3[type]*sin(3.0*phi)*siinv - 4.0*k4[type]*sin(4.0*phi)*siinv;
if (EFLAG) edihedral = k1[type]*(1.0 + c) + k2[type]*(1.0 - cos(2.0*phi))
+ k3[type]*(1.0 + cos(3.0*phi)) + k4[type]*(1.0 - cos(4.0*phi));
a = pd;
c = c * a;
s12 = s12 * a;
a11 = c*sb1*s1;
a22 = -sb2 * (2.0*c0*s12 - c*(s1+s2));
a33 = c*sb3*s2;
a12 = -r12c1 * (c1mag*c*s1 + c2mag*s12);
a13 = -rb1*rb3*s12;
a23 = r12c2 * (c2mag*c*s2 + c1mag*s12);
sx2 = a12*vb1x + a22*vb2x + a23*vb3x;
sy2 = a12*vb1y + a22*vb2y + a23*vb3y;
sz2 = a12*vb1z + a22*vb2z + a23*vb3z;
f1[0] = a11*vb1x + a12*vb2x + a13*vb3x;
f1[1] = a11*vb1y + a12*vb2y + a13*vb3y;
f1[2] = a11*vb1z + a12*vb2z + a13*vb3z;
f2[0] = -sx2 - f1[0];
f2[1] = -sy2 - f1[1];
f2[2] = -sz2 - f1[2];
f4[0] = a13*vb1x + a23*vb2x + a33*vb3x;
f4[1] = a13*vb1y + a23*vb2y + a33*vb3y;
f4[2] = a13*vb1z + a23*vb2z + a33*vb3z;
f3[0] = sx2 - f4[0];
f3[1] = sy2 - f4[1];
f3[2] = sz2 - f4[2];
// apply force to each of 4 atoms
if (NEWTON_BOND || i1 < nlocal) {
f[i1].x += f1[0];
f[i1].y += f1[1];
f[i1].z += f1[2];
}
if (NEWTON_BOND || i2 < nlocal) {
f[i2].x += f2[0];
f[i2].y += f2[1];
f[i2].z += f2[2];
}
if (NEWTON_BOND || i3 < nlocal) {
f[i3].x += f3[0];
f[i3].y += f3[1];
f[i3].z += f3[2];
}
if (NEWTON_BOND || i4 < nlocal) {
f[i4].x += f4[0];
f[i4].y += f4[1];
f[i4].z += f4[2];
}
if (EVFLAG)
ev_tally_thr(this,i1,i2,i3,i4,nlocal,NEWTON_BOND,edihedral,f1,f3,f4,
vb1x,vb1y,vb1z,vb2x,vb2y,vb2z,vb3x,vb3y,vb3z,thr);
}
}

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