/* ----------------------------------------------------------------------
   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: Stan Moore (Sandia)
------------------------------------------------------------------------- */

#include <math.h>
#include <stdlib.h>
#include "bond_fene_intel.h"
#include "atom.h"
#include "neighbor.h"
#include "domain.h"
#include "comm.h"
#include "force.h"
#include "memory.h"
#include "suffix.h"
#include "error.h"

using namespace LAMMPS_NS;

typedef struct { int a,b,t;  } int3_t;

/* ---------------------------------------------------------------------- */

BondFENEIntel::BondFENEIntel(LAMMPS *lmp) : BondFENE(lmp) 
{
  suffix_flag |= Suffix::INTEL;
}

/* ---------------------------------------------------------------------- */

BondFENEIntel::~BondFENEIntel()
{
}

/* ---------------------------------------------------------------------- */

void BondFENEIntel::compute(int eflag, int vflag)
{
  #ifdef _LMP_INTEL_OFFLOAD
  if (_use_base) {
    BondFENE::compute(eflag, vflag);
    return;
  }
  #endif

  if (fix->precision() == FixIntel::PREC_MODE_MIXED)
    compute<float,double>(eflag, vflag, fix->get_mixed_buffers(),
                          force_const_single);
  else if (fix->precision() == FixIntel::PREC_MODE_DOUBLE)
    compute<double,double>(eflag, vflag, fix->get_double_buffers(),
                           force_const_double);
  else
    compute<float,float>(eflag, vflag, fix->get_single_buffers(),
                         force_const_single);
}

/* ---------------------------------------------------------------------- */

template <class flt_t, class acc_t>
void BondFENEIntel::compute(int eflag, int vflag,
				IntelBuffers<flt_t,acc_t> *buffers,
				const ForceConst<flt_t> &fc)
{
  if (eflag || vflag) ev_setup(eflag,vflag);
  else evflag = 0;

  if (evflag) {
    if (eflag) {
      if (force->newton_bond)
	eval<1,1,1>(vflag, buffers, fc);
      else
	eval<1,1,0>(vflag, buffers, fc);
    } else {
      if (force->newton_bond)
	eval<1,0,1>(vflag, buffers, fc);
      else
	eval<1,0,0>(vflag, buffers, fc);
    }
  } else {
    if (force->newton_bond)
      eval<0,0,1>(vflag, buffers, fc);
    else
      eval<0,0,0>(vflag, buffers, fc);
  }
}

template <int EVFLAG, int EFLAG, int NEWTON_BOND, class flt_t, class acc_t>
void BondFENEIntel::eval(const int vflag, 
			     IntelBuffers<flt_t,acc_t> *buffers,
			     const ForceConst<flt_t> &fc)
{
  const int inum = neighbor->nbondlist;
  if (inum == 0) return;

  ATOM_T * _noalias const x = buffers->get_x(0);
  const int nlocal = atom->nlocal;
  const int nall = nlocal + atom->nghost;

  int f_stride;
  if (NEWTON_BOND) f_stride = buffers->get_stride(nall);
  else f_stride = buffers->get_stride(nlocal);

  int tc;
  FORCE_T * _noalias f_start;
  acc_t * _noalias ev_global;
  IP_PRE_get_buffers(0, buffers, fix, tc, f_start, ev_global);
  const int nthreads = tc;

  acc_t oebond, ov0, ov1, ov2, ov3, ov4, ov5;
  if (EVFLAG) {
    if (EFLAG)
      oebond = (acc_t)0.0;
    if (vflag) {
      ov0 = ov1 = ov2 = ov3 = ov4 = ov5 = (acc_t)0.0;
    }
  }


  #if defined(_OPENMP)
  #pragma omp parallel default(none) \
    shared(f_start,f_stride,fc)		  \
    reduction(+:oebond,ov0,ov1,ov2,ov3,ov4,ov5)
  #endif
  {
    int nfrom, nto, tid;
    IP_PRE_omp_range_id(nfrom, nto, tid, inum, nthreads);

    FORCE_T * _noalias const f = f_start + (tid * f_stride);
    if (fix->need_zero(tid))
      memset(f, 0, f_stride * sizeof(FORCE_T));

    const int3_t * _noalias const bondlist = 
      (int3_t *) neighbor->bondlist[0];

    for (int n = nfrom; n < nto; n++) {
      const int i1 = bondlist[n].a;
      const int i2 = bondlist[n].b;
      const int type = bondlist[n].t;

      const flt_t ir0sq = fc.fc[type].ir0sq;
      const flt_t k = fc.fc[type].k;
      const flt_t sigma = fc.fc[type].sigma;
      const flt_t sigmasq = sigma*sigma;
      const flt_t epsilon = fc.fc[type].epsilon;

      const flt_t delx = x[i1].x - x[i2].x;
      const flt_t dely = x[i1].y - x[i2].y;
      const flt_t delz = x[i1].z - x[i2].z;

      const flt_t rsq = delx*delx + dely*dely + delz*delz;
      flt_t rlogarg = (flt_t)1.0 - rsq * ir0sq;
      flt_t irsq = (flt_t)1.0 / rsq;

      // if r -> r0, then rlogarg < 0.0 which is an error
      // issue a warning and reset rlogarg = epsilon
      // if r > 2*r0 something serious is wrong, abort
      
      if (rlogarg < (flt_t)0.1) {
        char str[128];
        sprintf(str,"FENE bond too long: " BIGINT_FORMAT " "
                TAGINT_FORMAT " " TAGINT_FORMAT " %g",
                update->ntimestep,atom->tag[i1],atom->tag[i2],sqrt(rsq));
        error->warning(FLERR,str,0);
        if (rlogarg <= (flt_t)-3.0) error->one(FLERR,"Bad FENE bond");
        rlogarg = (flt_t)0.1;
      }
      
      flt_t fbond = -k/rlogarg;
      
      // force from LJ term
      
      flt_t sr2,sr6;
      if (rsq < (flt_t)TWO_1_3*sigmasq) {
	sr2 = sigmasq * irsq;
        sr6 = sr2 * sr2 * sr2;
        fbond += (flt_t)48.0 * epsilon * sr6 * (sr6 - (flt_t)0.5) * irsq;
      }
      
      // energy

      flt_t ebond;
      if (EFLAG) {
        ebond = (flt_t)-0.5 * k / ir0sq * log(rlogarg);
        if (rsq < (flt_t)TWO_1_3 * sigmasq)
          ebond += (flt_t)4.0 * epsilon * sr6 * (sr6 - (flt_t)1.0) + epsilon;
      }

      // apply force to each of 2 atoms

      if (NEWTON_BOND || i1 < nlocal) {
        f[i1].x += delx*fbond;
        f[i1].y += dely*fbond;
        f[i1].z += delz*fbond;
      }

      if (NEWTON_BOND || i2 < nlocal) {
        f[i2].x -= delx*fbond;
        f[i2].y -= dely*fbond;
        f[i2].z -= delz*fbond;
      }

      if (EVFLAG) {
	IP_PRE_ev_tally_bond(EFLAG, eatom, vflag, ebond, i1, i2, fbond, 
                             delx, dely, delz, oebond, f, NEWTON_BOND, 
                             nlocal, ov0, ov1, ov2, ov3, ov4, ov5);
      }
    } // for n
  } // omp parallel

  if (EVFLAG) {
    if (EFLAG)
      energy += oebond;
    if (vflag) {
      virial[0] += ov0; virial[1] += ov1; virial[2] += ov2;
      virial[3] += ov3; virial[4] += ov4; virial[5] += ov5; 
    }
  }

  fix->set_reduce_flag();
}

/* ---------------------------------------------------------------------- */

void BondFENEIntel::init_style()
{
  BondFENE::init_style();

  int ifix = modify->find_fix("package_intel");
  if (ifix < 0)
    error->all(FLERR,
               "The 'package intel' command is required for /intel styles");
  fix = static_cast<FixIntel *>(modify->fix[ifix]);

  #ifdef _LMP_INTEL_OFFLOAD
  _use_base = 0;
  if (fix->offload_balance() != 0.0) {
    _use_base = 1;
    return;
  }
  #endif

  fix->bond_init_check();

  if (fix->precision() == FixIntel::PREC_MODE_MIXED)
    pack_force_const(force_const_single, fix->get_mixed_buffers());
  else if (fix->precision() == FixIntel::PREC_MODE_DOUBLE)
    pack_force_const(force_const_double, fix->get_double_buffers());
  else
    pack_force_const(force_const_single, fix->get_single_buffers());
}

/* ---------------------------------------------------------------------- */

template <class flt_t, class acc_t>
void BondFENEIntel::pack_force_const(ForceConst<flt_t> &fc,
                                         IntelBuffers<flt_t,acc_t> *buffers)
{
  const int bp1 = atom->nbondtypes + 1;
  fc.set_ntypes(bp1,memory);

  for (int i = 0; i < bp1; i++) {
    fc.fc[i].k = k[i];
    fc.fc[i].ir0sq = 1.0 / (r0[i] * r0[i]);
    fc.fc[i].sigma = sigma[i];
    fc.fc[i].epsilon = epsilon[i];
  }
}

/* ---------------------------------------------------------------------- */

template <class flt_t>
void BondFENEIntel::ForceConst<flt_t>::set_ntypes(const int nbondtypes,
	                                              Memory *memory) {
  if (nbondtypes != _nbondtypes) {
    if (_nbondtypes > 0)
      _memory->destroy(fc);
    
    if (nbondtypes > 0)
      _memory->create(fc,nbondtypes,"bondfeneintel.fc");
  }
  _nbondtypes = nbondtypes;
  _memory = memory;
}
