git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@8192 f3b2605a-c512-4ea7-a41b-209d697bcdaa

src/USER-OMP/improper_cossq_omp.cpp

+/* ----------------------------------------------------------------------
+   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 "improper_cossq_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
+
+/* ---------------------------------------------------------------------- */
+
+ImproperCossqOMP::ImproperCossqOMP(class LAMMPS *lmp)
+  : ImproperCossq(lmp), ThrOMP(lmp,THR_IMPROPER)
+{
+  suffix_flag |= Suffix::OMP;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void ImproperCossqOMP::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->nimproperlist;
+
+#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 ImproperCossqOMP::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;
+  double eimproper,f1[3],f2[3],f3[3],f4[3];
+  double rjisq, rji, rlksq, rlk, cosphi, angfac;
+  double cjiji, clkji, clklk, cfact1, cfact2, cfact3;
+
+  eimproper = 0.0;
+
+  const double * const * const x = atom->x;
+  double * const * const f = thr->get_f();
+  const int * const * const improperlist = neighbor->improperlist;
+  const int nlocal = atom->nlocal;
+
+  for (n = nfrom; n < nto; n++) {
+    i1 = improperlist[n][0];
+    i2 = improperlist[n][1];
+    i3 = improperlist[n][2];
+    i4 = improperlist[n][3];
+    type = improperlist[n][4];
+
+    /* separation vector between i1 and i2, (i2-i1) */
+    vb1x = x[i2][0] - x[i1][0];
+    vb1y = x[i2][1] - x[i1][1];
+    vb1z = x[i2][2] - x[i1][2];
+    domain->minimum_image(vb1x,vb1y,vb1z);
+    rjisq = vb1x*vb1x + vb1y*vb1y + vb1z*vb1z ;
+    rji = sqrt(rjisq);
+
+    /* separation vector between i2 and i3 (i3-i2) */
+    vb2x = x[i3][0] - x[i2][0];
+    vb2y = x[i3][1] - x[i2][1];
+    vb2z = x[i3][2] - x[i2][2];
+    domain->minimum_image(vb2x,vb2y,vb2z);
+
+    /* separation vector between i3 and i4, (i4-i3) */
+    vb3x = x[i4][0] - x[i3][0];
+    vb3y = x[i4][1] - x[i3][1];
+    vb3z = x[i4][2] - x[i3][2];
+    domain->minimum_image(vb3x,vb3y,vb3z);
+    rlksq = vb3x*vb3x + vb3y*vb3y + vb3z*vb3z ;
+    rlk = sqrt(rlksq);
+
+    cosphi = (vb3x*vb1x + vb3y*vb1y + vb3z*vb1z)/(rji * rlk);
+     
+    /* Check that cos(phi) is in the correct limits. */     
+    if (cosphi > 1.0 + TOLERANCE || cosphi < (-1.0 - TOLERANCE)) {
+      int me = comm->me;
+
+      if (screen) {
+	char str[128];
+	sprintf(str,"Improper problem: %d/%d " BIGINT_FORMAT " %d %d %d %d",
+		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][0],x[i1][1],x[i1][2]);
+	fprintf(screen,"  2nd atom: %d %g %g %g\n",
+		me,x[i2][0],x[i2][1],x[i2][2]);
+	fprintf(screen,"  3rd atom: %d %g %g %g\n",
+		me,x[i3][0],x[i3][1],x[i3][2]);
+	fprintf(screen,"  4th atom: %d %g %g %g\n",
+		me,x[i4][0],x[i4][1],x[i4][2]);
+      }
+
+      
+      /* Apply corrections to round-off errors. */
+      if (cosphi > 1.0)  cosphi -= SMALL;
+      if (cosphi < -1.0) cosphi += SMALL;
+      
+      /* Calculate the angle: */
+      double torangle = acos(cosphi);
+      cosphi = cos(torangle - chi[type]);
+
+      if (EFLAG) eimproper = 0.5 * k[type] * cosphi * cosphi;
+     
+      /*
+	printf("The tags: %d-%d-%d-%d, of type %d .\n",atom->tag[i1],atom->tag[i2],atom->tag[i3],atom->tag[i4],type);   
+	printf("The ji vector: %f, %f, %f.\nThe lk vector: %f, %f, %f.\n", vb1x,vb1y,vb1z,vb3x,vb3y,vb3z);
+	printf("The cosine of the angle: %-1.16e.\n", cosphi);
+	printf("The energy of the improper: %-1.16e with prefactor %-1.16e.\n", eimproper, 0.5*k[type]);
+      */
+
+      /* Work out forces. */
+      angfac = - k[type] * cosphi;
+
+      cjiji = rjisq;
+      clklk = rlksq;
+      /*CLKJI = RXLK * RXJI + RYLK * RYJI + RZLK * RZJI */
+      clkji = vb3x*vb1x + vb3y*vb1y + vb3z*vb1z; 
+
+      /*CFACT1 = CLKLK * CJIJI
+	CFACT1 = SQRT(CFACT1)
+	CFACT1 = ANGFAC / CFACT1*/
+      cfact1 = angfac / sqrt(clklk * cjiji);
+      /*CFACT2 = CLKJI / CLKLK*/
+      cfact2 = clkji / clklk;
+      /*CFACT3 = CLKJI / CJIJI*/
+      cfact3 = clkji / cjiji;
+
+      /*FIX = -RXLK + CFACT3 * RXJI
+	FIY = -RYLK + CFACT3 * RYJI
+	FIZ = -RZLK + CFACT3 * RZJI*/
+      f1[0] = - vb3x + cfact3 * vb1x;
+      f1[1] = - vb3y + cfact3 * vb1y;
+      f1[2] = - vb3z + cfact3 * vb1z;
+
+      /*FJX = -FIX
+	FJY = -FIY
+	FJZ = -FIZ*/
+      f2[0] = - f1[0];
+      f2[1] = - f1[1];
+      f2[2] = - f1[2];
+      
+      /*FKX = CFACT2 * RXLK - RXJI
+	FKY = CFACT2 * RYLK - RYJI
+	FKZ = CFACT2 * RZLK - RZJI*/
+      f3[0] = cfact2 * vb3x - vb1x;
+      f3[1] = cfact2 * vb3y - vb1y;
+      f3[2] = cfact2 * vb3z - vb1z;
+
+      /*FLX = -FKX
+	FLY = -FKY
+	FLZ = -FKZ*/
+      f4[0] = - f3[0];
+      f4[1] = - f3[1];
+      f4[2] = - f3[2];
+
+      /*FIX = FIX * CFACT1
+	FIY = FIY * CFACT1
+	FIZ = FIZ * CFACT1*/
+      f1[0] *= cfact1;
+      f1[1] *= cfact1; 
+      f1[2] *= cfact1;
+
+      /*FJX = FJX * CFACT1
+	FJY = FJY * CFACT1
+	FJZ = FJZ * CFACT1*/
+      f2[0] *= cfact1;
+      f2[1] *= cfact1;
+      f2[2] *= cfact1;
+
+      /*FKX = FKX * CFACT1
+	FKY = FKY * CFACT1
+	FKZ = FKZ * CFACT1*/
+      f3[0] *= cfact1; 
+      f3[1] *= cfact1; 
+      f3[2] *= cfact1;
+
+      /*FLX = FLX * CFACT1
+	FLY = FLY * CFACT1
+	FLZ = FLZ * CFACT1*/
+      f4[0] *= cfact1;
+      f4[1] *= cfact1; 
+      f4[2] *= cfact1;
+
+      /* Apply force to each of 4 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] += f2[0];
+	f[i2][1] += f2[1];
+	f[i2][2] += f2[2];
+      }
+
+      if (NEWTON_BOND || i3 < nlocal) {
+	f[i3][0] += f3[0];
+	f[i3][1] += f3[1];
+	f[i3][2] += f3[2];
+      }
+
+      if (NEWTON_BOND || i4 < nlocal) {
+	f[i4][0] += f4[0];
+	f[i4][1] += f4[1];
+	f[i4][2] += f4[2];
+      }
+
+      if (EVFLAG)
+	ev_tally_thr(this,i1,i2,i3,i4,nlocal,NEWTON_BOND,eimproper,f1,f3,f4,
+		     -vb1x,-vb1y,-vb1z,vb2x,vb2y,vb2z,vb3x,vb3y,vb3z,thr);
+    }
+  }
+}
+

src/USER-OMP/improper_cossq_omp.h

+/* -*- c++ -*- ----------------------------------------------------------
+   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)
+------------------------------------------------------------------------- */
+
+#ifdef IMPROPER_CLASS
+
+ImproperStyle(cossq/omp,ImproperCossqOMP)
+
+#else
+
+#ifndef LMP_IMPROPER_COSSQ_OMP_H
+#define LMP_IMPROPER_COSSQ_OMP_H
+
+#include "improper_cossq.h"
+#include "thr_omp.h"
+
+namespace LAMMPS_NS {
+
+class ImproperCossqOMP : public ImproperCossq, public ThrOMP {
+
+ public:
+  ImproperCossqOMP(class LAMMPS *lmp);
+  virtual void compute(int, int);
+
+ private:
+  template <int EVFLAG, int EFLAG, int NEWTON_BOND>
+  void eval(int ifrom, int ito, ThrData * const thr);
+};
+
+}
+
+#endif
+#endif

src/USER-OMP/improper_ring_omp.cpp

+/* ----------------------------------------------------------------------
+   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 "improper_ring_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
+
+/* ---------------------------------------------------------------------- */
+
+ImproperRingOMP::ImproperRingOMP(class LAMMPS *lmp)
+  : ImproperRing(lmp), ThrOMP(lmp,THR_IMPROPER)
+{
+  suffix_flag |= Suffix::OMP;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void ImproperRingOMP::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->nimproperlist;
+
+#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 ImproperRingOMP::eval(int nfrom, int nto, ThrData * const thr)
+{
+  /* Be careful!: "chi" is the equilibrium angle in radians. */
+  int i1,i2,i3,i4,n,type;
+
+  double eimproper;
+
+  /* Compatibility variables. */
+  double vb1x,vb1y,vb1z,vb2x,vb2y,vb2z,vb3x,vb3y,vb3z;
+  double f1[3], f3[3], f4[3];
+   
+  /* Actual computation variables. */
+  int at1[3], at2[3], at3[3], icomb;
+  double   bvec1x[3], bvec1y[3], bvec1z[3], 
+    bvec2x[3], bvec2y[3], bvec2z[3], 
+    bvec1n[3], bvec2n[3], bend_angle[3];
+  double   angle_summer, angfac, cfact1, cfact2, cfact3;
+  double   cjiji, ckjji, ckjkj, fix, fiy, fiz, fjx, fjy, fjz, fkx, fky, fkz;
+  
+  eimproper = 0.0;
+
+  const double * const * const x = atom->x;
+  double * const * const f = thr->get_f();
+  const int * const * const improperlist = neighbor->improperlist;
+  const int nlocal = atom->nlocal;
+
+  /* A description of the potential can be found in 
+     Macromolecules 35, pp. 1463-1472 (2002). */
+  for (n = nfrom; n < nto; n++) {
+    /* Take the ids of the atoms contributing to the improper potential. */
+    i1 = improperlist[n][0];   /* Atom "1" of Figure 1 from the above reference.*/
+    i2 = improperlist[n][1];   /* Atom "2" ... */
+    i3 = improperlist[n][2];   /* Atom "3" ... */
+    i4 = improperlist[n][3];   /* Atom "9" ... */
+    type = improperlist[n][4];
+
+    /* Calculate the necessary variables for LAMMPS implementation. 
+       if (evflag) ev_tally(i1,i2,i3,i4,nlocal,newton_bond,eimproper,f1,f3,f4,
+       vb1x,vb1y,vb1z,vb2x,vb2y,vb2z,vb3x,vb3y,vb3z);  
+       Although, they are irrelevant to the calculation of the potential, we keep
+       them for maximal compatibility. */
+    vb1x = x[i1][0] - x[i2][0]; vb1y = x[i1][1] - x[i2][1]; vb1z = x[i1][2] - x[i2][2];
+    domain->minimum_image(vb1x,vb1y,vb1z);
+
+    vb2x = x[i3][0] - x[i2][0]; vb2y = x[i3][1] - x[i2][1]; vb2z = x[i3][2] - x[i2][2];
+    domain->minimum_image(vb2x,vb2y,vb2z);
+
+    vb3x = x[i4][0] - x[i3][0]; vb3y = x[i4][1] - x[i3][1]; vb3z = x[i4][2] - x[i3][2];
+    domain->minimum_image(vb3x,vb3y,vb3z);
+
+  
+    /* Pass the atom tags to form the necessary combinations. */
+    at1[0] = i1; at2[0] = i2; at3[0] = i4;  /* ids: 1-2-9 */
+    at1[1] = i1; at2[1] = i2; at3[1] = i3;  /* ids: 1-2-3 */
+    at1[2] = i4; at2[2] = i2; at3[2] = i3;  /* ids: 9-2-3 */
+      
+
+    /* Initialize the sum of the angles differences. */
+    angle_summer = 0.0;
+    /* Take a loop over the three angles, defined by each triad: */
+    for (icomb = 0; icomb < 3; icomb ++) {
+         
+      /* Bond vector connecting the first and the second atom. */
+      bvec1x[icomb] = x[at2[icomb]][0] - x[at1[icomb]][0];
+      bvec1y[icomb] = x[at2[icomb]][1] - x[at1[icomb]][1];
+      bvec1z[icomb] = x[at2[icomb]][2] - x[at1[icomb]][2];
+      domain -> minimum_image(bvec1x[icomb], bvec1y[icomb], bvec1z[icomb]);
+      /* also calculate the norm of the vector: */
+      bvec1n[icomb] = sqrt(  bvec1x[icomb]*bvec1x[icomb] 
+			     + bvec1y[icomb]*bvec1y[icomb] 
+			     + bvec1z[icomb]*bvec1z[icomb]);
+      /* Bond vector connecting the second and the third atom. */
+      bvec2x[icomb] = x[at3[icomb]][0] - x[at2[icomb]][0];
+      bvec2y[icomb] = x[at3[icomb]][1] - x[at2[icomb]][1];
+      bvec2z[icomb] = x[at3[icomb]][2] - x[at2[icomb]][2];
+      domain -> minimum_image(bvec2x[icomb], bvec2y[icomb], bvec2z[icomb]);
+      /* also calculate the norm of the vector: */
+      bvec2n[icomb] = sqrt(  bvec2x[icomb]*bvec2x[icomb] 
+			     + bvec2y[icomb]*bvec2y[icomb] 
+			     + bvec2z[icomb]*bvec2z[icomb]);
+        
+      /* Calculate the bending angle of the atom triad: */
+      bend_angle[icomb] = (  bvec2x[icomb]*bvec1x[icomb] 
+			     + bvec2y[icomb]*bvec1y[icomb] 
+			     + bvec2z[icomb]*bvec1z[icomb]);
+      bend_angle[icomb] /= (bvec1n[icomb] * bvec2n[icomb]);
+      if (bend_angle[icomb] >  1.0) bend_angle[icomb] -= SMALL;
+      if (bend_angle[icomb] < -1.0) bend_angle[icomb] += SMALL;
+
+      /* Append the current angle to the sum of angle differences. */
+      angle_summer += (bend_angle[icomb] - chi[type]);
+    } 
+    if (EFLAG) eimproper = (1.0/6.0) *k[type] * pow(angle_summer,6); 
+    /*
+      printf("The tags: %d-%d-%d-%d, of type %d .\n",atom->tag[i1],atom->tag[i2],atom->tag[i3],atom->tag[i4],type);   
+      // printf("The coordinates of the first: %f, %f, %f.\n", x[i1][0], x[i1][1], x[i1][2]);
+      // printf("The coordinates of the second: %f, %f, %f.\n", x[i2][0], x[i2][1], x[i2][2]);
+      // printf("The coordinates of the third: %f, %f, %f.\n", x[i3][0], x[i3][1], x[i3][2]);
+      // printf("The coordinates of the fourth: %f, %f, %f.\n", x[i4][0], x[i4][1], x[i4][2]);
+      printf("The angles are: %f / %f / %f equilibrium: %f.\n", bend_angle[0], bend_angle[1], bend_angle[2],chi[type]);
+      printf("The energy of the improper: %f with prefactor %f.\n", eimproper,(1.0/6.0)*k[type]);
+      printf("The sum of the angles: %f.\n", angle_summer); 
+    */
+
+    /* Force calculation acting on all atoms. 
+       Calculate the derivatives of the potential. */
+    angfac = k[type] * pow(angle_summer,5);
+
+    f1[0] = 0.0; f1[1] = 0.0; f1[2] = 0.0;
+    f3[0] = 0.0; f3[1] = 0.0; f3[2] = 0.0;
+    f4[0] = 0.0; f4[1] = 0.0; f4[2] = 0.0; 
+      
+    /* Take a loop over the three angles, defined by each triad: */
+    for (icomb = 0; icomb < 3; icomb ++)
+      {
+	/* Calculate the squares of the distances. */
+	cjiji = bvec1n[icomb] * bvec1n[icomb];  ckjkj = bvec2n[icomb] * bvec2n[icomb];
+         
+	ckjji =   bvec2x[icomb] * bvec1x[icomb] 
+	  + bvec2y[icomb] * bvec1y[icomb]
+	  + bvec2z[icomb] * bvec1z[icomb] ;
+         
+	cfact1 = angfac / (sqrt(ckjkj * cjiji)); 
+	cfact2 = ckjji / ckjkj;
+	cfact3 = ckjji / cjiji;
+
+	/* Calculate the force acted on the thrid atom of the angle. */
+	fkx = cfact2 * bvec2x[icomb] - bvec1x[icomb];
+	fky = cfact2 * bvec2y[icomb] - bvec1y[icomb];
+	fkz = cfact2 * bvec2z[icomb] - bvec1z[icomb];
+         
+	/* Calculate the force acted on the first atom of the angle. */
+	fix = bvec2x[icomb] - cfact3 * bvec1x[icomb];
+	fiy = bvec2y[icomb] - cfact3 * bvec1y[icomb];
+	fiz = bvec2z[icomb] - cfact3 * bvec1z[icomb];       
+
+	/* Finally, calculate the force acted on the middle atom of the angle.*/
+	fjx = - fix - fkx;  fjy = - fiy - fky;  fjz = - fiz - fkz;  
+ 
+	/* Consider the appropriate scaling of the forces: */
+	fix *= cfact1; fiy *= cfact1; fiz *= cfact1;
+	fjx *= cfact1; fjy *= cfact1; fjz *= cfact1;
+	fkx *= cfact1; fky *= cfact1; fkz *= cfact1;
+
+	if      (at1[icomb] == i1)  {f1[0] += fix; f1[1] += fiy; f1[2] += fiz;}
+	else if (at2[icomb] == i1)  {f1[0] += fjx; f1[1] += fjy; f1[2] += fjz;}
+	else if (at3[icomb] == i1)  {f1[0] += fkx; f1[1] += fky; f1[2] += fkz;}
+ 
+	if      (at1[icomb] == i3)  {f3[0] += fix; f3[1] += fiy; f3[2] += fiz;}
+	else if (at2[icomb] == i3)  {f3[0] += fjx; f3[1] += fjy; f3[2] += fjz;}
+	else if (at3[icomb] == i3)  {f3[0] += fkx; f3[1] += fky; f3[2] += fkz;}
+
+	if      (at1[icomb] == i4)  {f4[0] += fix; f4[1] += fiy; f4[2] += fiz;}
+	else if (at2[icomb] == i4)  {f4[0] += fjx; f4[1] += fjy; f4[2] += fjz;}
+	else if (at3[icomb] == i4)  {f4[0] += fkx; f4[1] += fky; f4[2] += fkz;}
+
+
+	/* Store the contribution to the global arrays: */
+	/* Take the id of the atom from the at1[icomb] element, i1 = at1[icomb]. */
+	if (NEWTON_BOND || at1[icomb] < nlocal) {
+	  f[at1[icomb]][0] += fix;  
+	  f[at1[icomb]][1] += fiy;
+	  f[at1[icomb]][2] += fiz;
+	}
+	/* Take the id of the atom from the at2[icomb] element, i2 = at2[icomb]. */
+	if (NEWTON_BOND || at2[icomb] < nlocal) {
+	  f[at2[icomb]][0] += fjx;
+	  f[at2[icomb]][1] += fjy;
+	  f[at2[icomb]][2] += fjz;
+	}
+	/* Take the id of the atom from the at3[icomb] element, i3 = at3[icomb]. */
+	if (NEWTON_BOND || at3[icomb] < nlocal) {
+	  f[at3[icomb]][0] += fkx;
+	  f[at3[icomb]][1] += fky;
+	  f[at3[icomb]][2] += fkz;
+	}
+   
+      }
+
+    if (EVFLAG)
+      ev_tally_thr(this,i1,i2,i3,i4,nlocal,NEWTON_BOND,eimproper,f1,f3,f4,
+		   vb1x,vb1y,vb1z,vb2x,vb2y,vb2z,vb3x,vb3y,vb3z,thr);
+  }
+}

src/USER-OMP/improper_ring_omp.h

+/* -*- c++ -*- ----------------------------------------------------------
+   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)
+------------------------------------------------------------------------- */
+
+#ifdef IMPROPER_CLASS
+
+ImproperStyle(ring/omp,ImproperRingOMP)
+
+#else
+
+#ifndef LMP_IMPROPER_RING_OMP_H
+#define LMP_IMPROPER_RING_OMP_H
+
+#include "improper_ring.h"
+#include "thr_omp.h"
+
+namespace LAMMPS_NS {
+
+class ImproperRingOMP : public ImproperRing, public ThrOMP {
+
+ public:
+  ImproperRingOMP(class LAMMPS *lmp);
+  virtual void compute(int, int);
+
+ private:
+  template <int EVFLAG, int EFLAG, int NEWTON_BOND>
+  void eval(int ifrom, int ito, ThrData * const thr);
+};
+
+}
+
+#endif
+#endif