text: /* ----------------------------------------------------------------------
     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)
     This style is a simplified re-implementation of the CG/CMM pair style
  ------------------------------------------------------------------------- */
  
  #include <cmath>
  #include <cstdio>
  #include <cstdlib>
  #include <cstring>
  #include "pair_lj_sdk_coul_msm.h"
  #include "atom.h"
  #include "comm.h"
  #include "force.h"
  #include "kspace.h"
  #include "neighbor.h"
  #include "neigh_list.h"
  #include "neigh_request.h"
  #include "update.h"
  #include "integrate.h"
  #include "math_const.h"
  #include "memory.h"
  #include "error.h"
  
  #include "lj_sdk_common.h"
  
  using namespace LAMMPS_NS;
  using namespace MathConst;
  using namespace LJSDKParms;
  
  /* ---------------------------------------------------------------------- */
  
  PairLJSDKCoulMSM::PairLJSDKCoulMSM(LAMMPS *lmp) : PairLJSDKCoulLong(lmp)
  {
    ewaldflag = pppmflag = 0;
    msmflag = 1;
    respa_enable = 0;
    ftable = NULL;
  }
  
  /* ---------------------------------------------------------------------- */
  
  void PairLJSDKCoulMSM::compute(int eflag, int vflag)
  {
    if (force->kspace->scalar_pressure_flag)
      error->all(FLERR,"Must use 'kspace_modify pressure/scalar no' with Pair style");
  
    ev_init(eflag,vflag);
  
    if (evflag) {
      if (eflag) {
        if (force->newton_pair) eval_msm<1,1,1>();
        else eval_msm<1,1,0>();
      } else {
        if (force->newton_pair) eval_msm<1,0,1>();
        else eval_msm<1,0,0>();
      }
    } else {
      if (force->newton_pair) eval_msm<0,0,1>();
      else eval_msm<0,0,0>();
    }
  
    if (vflag_fdotr) virial_fdotr_compute();
  }
  
  /* ---------------------------------------------------------------------- */
  
  template <int EVFLAG, int EFLAG, int NEWTON_PAIR>
  void PairLJSDKCoulMSM::eval_msm()
  {
    int i,ii,j,jj,jtype,itable;
    double qtmp,xtmp,ytmp,ztmp,delx,dely,delz,evdwl,ecoul,fpair;
    double fraction,table;
    double r,rsq,r2inv,forcecoul,forcelj,factor_coul,factor_lj;
    double egamma,fgamma,prefactor;
  
    const double * const * const x = atom->x;
    double * const * const f = atom->f;
    const double * const q = atom->q;
    const int * const type = atom->type;
    const int nlocal = atom->nlocal;
    const double * const special_coul = force->special_coul;
    const double * const special_lj = force->special_lj;
    const double qqrd2e = force->qqrd2e;
    double fxtmp,fytmp,fztmp;
  
    const int inum = list->inum;
    const int * const ilist = list->ilist;
    const int * const numneigh = list->numneigh;
    const int * const * const firstneigh = list->firstneigh;
  
    // loop over neighbors of my atoms
  
    for (ii = 0; ii < inum; ii++) {
  
      i = ilist[ii];
      qtmp = q[i];
      xtmp = x[i][0];
      ytmp = x[i][1];
      ztmp = x[i][2];
      fxtmp=fytmp=fztmp=0.0;
  
      const int itype = type[i];
      const int * const jlist = firstneigh[i];
      const int jnum = numneigh[i];
  
      for (jj = 0; jj < jnum; jj++) {
        forcecoul = forcelj = evdwl = ecoul = 0.0;
  
        j = jlist[jj];
        factor_lj = special_lj[sbmask(j)];
        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;
        jtype = type[j];
  
        if (rsq < cutsq[itype][jtype]) {
          r2inv = 1.0/rsq;
          const int ljt = lj_type[itype][jtype];
  
          if (rsq < cut_coulsq) {
            if (!ncoultablebits || rsq <= tabinnersq) {
              r = sqrt(rsq);
              prefactor = qqrd2e * qtmp*q[j]/r;
              fgamma = 1.0 + (rsq/cut_coulsq)*force->kspace->dgamma(r/cut_coul);
              forcecoul = prefactor * fgamma;
              if (EFLAG) {
                egamma = 1.0 - (r/cut_coul)*force->kspace->gamma(r/cut_coul);
                ecoul = prefactor*egamma;
              }
              if (factor_coul < 1.0) {
                forcecoul -= (1.0-factor_coul)*prefactor;
                if (EFLAG) ecoul -= (1.0-factor_coul)*prefactor;
              }
            } else {
              union_int_float_t rsq_lookup;
              rsq_lookup.f = rsq;
              itable = rsq_lookup.i & ncoulmask;
              itable >>= ncoulshiftbits;
              fraction = (rsq_lookup.f - rtable[itable]) * drtable[itable];
              table = ftable[itable] + fraction*dftable[itable];
              forcecoul = qtmp*q[j] * table;
              if (EFLAG) ecoul = qtmp*q[j] *
                (etable[itable] + fraction*detable[itable]);
              if (factor_coul < 1.0) {
                table = ctable[itable] + fraction*dctable[itable];
                prefactor = qtmp*q[j] * table;
                forcecoul -= (1.0-factor_coul)*prefactor;
                if (EFLAG) ecoul -= (1.0-factor_coul)*prefactor;
              }
            }
          } else forcecoul = 0.0;
  
          if (rsq < cut_ljsq[itype][jtype]) {
  
            if (ljt == LJ12_4) {
              const double r4inv=r2inv*r2inv;
              forcelj = r4inv*(lj1[itype][jtype]*r4inv*r4inv
                               - lj2[itype][jtype]);
  
              if (EFLAG)
                evdwl = r4inv*(lj3[itype][jtype]*r4inv*r4inv
                               - lj4[itype][jtype]) - offset[itype][jtype];
  
            } else if (ljt == LJ9_6) {
              const double r3inv = r2inv*sqrt(r2inv);
              const double r6inv = r3inv*r3inv;
              forcelj = r6inv*(lj1[itype][jtype]*r3inv
                               - lj2[itype][jtype]);
              if (EFLAG)
                evdwl = r6inv*(lj3[itype][jtype]*r3inv
                               - lj4[itype][jtype]) - offset[itype][jtype];
  
            } else if (ljt == LJ12_6) {
              const double r6inv = r2inv*r2inv*r2inv;
              forcelj = r6inv*(lj1[itype][jtype]*r6inv
                               - lj2[itype][jtype]);
              if (EFLAG)
                evdwl = r6inv*(lj3[itype][jtype]*r6inv
                               - lj4[itype][jtype]) - offset[itype][jtype];
            }
            forcelj *= factor_lj;
            if (EFLAG) evdwl *= factor_lj;
          }
  
          fpair = (forcecoul + forcelj) * r2inv;
  
          fxtmp += delx*fpair;
          fytmp += dely*fpair;
          fztmp += 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,
                               evdwl,ecoul,fpair,delx,dely,delz);
        }
      }
      f[i][0] += fxtmp;
      f[i][1] += fytmp;
      f[i][2] += fztmp;
    }
  }
  
  /* ---------------------------------------------------------------------- */
  
  double PairLJSDKCoulMSM::single(int i, int j, int itype, int jtype,
                                   double rsq,
                                   double factor_coul, double factor_lj,
                                   double &fforce)
  {
    double r2inv,r,fgamma,egamma,prefactor;
    double fraction,table,forcecoul,forcelj,phicoul,philj;
    int itable;
  
    forcecoul = forcelj = phicoul = philj = 0.0;
  
    r2inv = 1.0/rsq;
    if (rsq < cut_coulsq) {
      if (!ncoultablebits || rsq <= tabinnersq) {
        r = sqrt(rsq);
        prefactor = force->qqrd2e * atom->q[i]*atom->q[j]/r;
        egamma = 1.0 - (r/cut_coul)*force->kspace->gamma(r/cut_coul);
        fgamma = 1.0 + (rsq/cut_coulsq)*force->kspace->dgamma(r/cut_coul);
        forcecoul = prefactor * fgamma;
        phicoul = prefactor * egamma;
        if (factor_coul < 1.0) {
          forcecoul -= (1.0-factor_coul)*prefactor;
          phicoul -= (1.0-factor_coul)*prefactor;
        }
      } else {
        union_int_float_t rsq_lookup_single;
        rsq_lookup_single.f = rsq;
        itable = rsq_lookup_single.i & ncoulmask;
        itable >>= ncoulshiftbits;
        fraction = (rsq_lookup_single.f - rtable[itable]) * drtable[itable];
        table = ftable[itable] + fraction*dftable[itable];
        forcecoul = atom->q[i]*atom->q[j] * table;
        table = etable[itable] + fraction*detable[itable];
        phicoul = atom->q[i]*atom->q[j] * table;
        if (factor_coul < 1.0) {
          table = ctable[itable] + fraction*dctable[itable];
          prefactor = atom->q[i]*atom->q[j] * table;
          forcecoul -= (1.0-factor_coul)*prefactor;
          phicoul -= (1.0-factor_coul)*prefactor;
        }
      }
    }
  
    if (rsq < cut_ljsq[itype][jtype]) {
      const int ljt = lj_type[itype][jtype];
      const double ljpow1 = lj_pow1[ljt];
      const double ljpow2 = lj_pow2[ljt];
      const double ljpref = lj_prefact[ljt];
  
      const double ratio = sigma[itype][jtype]/sqrt(rsq);
      const double eps = epsilon[itype][jtype];
  
      forcelj = factor_lj * ljpref*eps * (ljpow1*pow(ratio,ljpow1)
                            - ljpow2*pow(ratio,ljpow2))/rsq;
      philj = factor_lj * (ljpref*eps * (pow(ratio,ljpow1) - pow(ratio,ljpow2))
                           - offset[itype][jtype]);
    }
  
    fforce = (forcecoul + forcelj) * r2inv;
  
    return phicoul + philj;
  }
  
  /* ---------------------------------------------------------------------- */
  
  void *PairLJSDKCoulMSM::extract(const char *str, int &dim)
  {
    dim = 2;
    if (strcmp(str,"epsilon") == 0) return (void *) epsilon;
    if (strcmp(str,"sigma") == 0) return (void *) sigma;
    if (strcmp(str,"lj_type") == 0) return (void *) lj_type;
    if (strcmp(str,"lj1") == 0) return (void *) lj1;
    if (strcmp(str,"lj2") == 0) return (void *) lj2;
    if (strcmp(str,"lj3") == 0) return (void *) lj3;
    if (strcmp(str,"lj4") == 0) return (void *) lj4;
    if (strcmp(str,"rminsq") == 0) return (void *) rminsq;
    if (strcmp(str,"emin") == 0) return (void *) emin;
  
    dim = 0;
    if (strcmp(str,"cut_coul") == 0) return (void *) &cut_coul;
    if (strcmp(str,"cut_msm") == 0) return (void *) &cut_coul;
    return NULL;
  }
  
  