/* ----------------------------------------------------------------------
   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 (SNL)
------------------------------------------------------------------------- */

#include "pair_coul_wolf_kokkos.h"
#include <cmath>
#include "kokkos.h"
#include "atom_kokkos.h"
#include "force.h"
#include "neighbor.h"
#include "neigh_list_kokkos.h"
#include "neigh_request.h"
#include "math_const.h"
#include "memory_kokkos.h"
#include "error.h"
#include "atom_masks.h"

using namespace LAMMPS_NS;
using namespace MathConst;

#define KOKKOS_CUDA_MAX_THREADS 256
#define KOKKOS_CUDA_MIN_BLOCKS 8

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

template<class DeviceType>
PairCoulWolfKokkos<DeviceType>::PairCoulWolfKokkos(LAMMPS *lmp) : PairCoulWolf(lmp)
{
  respa_enable = 0;

  atomKK = (AtomKokkos *) atom;
  execution_space = ExecutionSpaceFromDevice<DeviceType>::space;
  datamask_read = X_MASK | F_MASK | TYPE_MASK | Q_MASK | ENERGY_MASK | VIRIAL_MASK;
  datamask_modify = F_MASK | ENERGY_MASK | VIRIAL_MASK;
}

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

template<class DeviceType>
PairCoulWolfKokkos<DeviceType>::~PairCoulWolfKokkos()
{
  if (!copymode) {
    memoryKK->destroy_kokkos(k_eatom,eatom);
    memoryKK->destroy_kokkos(k_vatom,vatom);
  }
}

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

template<class DeviceType>
void PairCoulWolfKokkos<DeviceType>::compute(int eflag_in, int vflag_in)
{
  eflag = eflag_in;
  vflag = vflag_in;

  if (neighflag == FULL) no_virial_fdotr_compute = 1;

  ev_init(eflag,vflag,0);

  // reallocate per-atom arrays if necessary

  if (eflag_atom) {
    memoryKK->destroy_kokkos(k_eatom,eatom);
    memoryKK->create_kokkos(k_eatom,eatom,maxeatom,"pair:eatom");
    d_eatom = k_eatom.view<DeviceType>();
  }
  if (vflag_atom) {
    memoryKK->destroy_kokkos(k_vatom,vatom);
    memoryKK->create_kokkos(k_vatom,vatom,maxvatom,"pair:vatom");
    d_vatom = k_vatom.view<DeviceType>();
  }

  atomKK->sync(execution_space,datamask_read);
  if (eflag || vflag) atomKK->modified(execution_space,datamask_modify);
  else atomKK->modified(execution_space,F_MASK);

  // shifted coulombic energy

  e_shift = erfc(alf*cut_coul)/cut_coul;
  f_shift = -(e_shift+ 2.0*alf/MY_PIS * exp(-alf*alf*cut_coul*cut_coul)) /
    cut_coul;

  x = atomKK->k_x.view<DeviceType>();
  f = atomKK->k_f.view<DeviceType>();
  q = atomKK->k_q.view<DeviceType>();
  nlocal = atom->nlocal;
  nall = atom->nlocal + atom->nghost;
  newton_pair = force->newton_pair;

  NeighListKokkos<DeviceType>* k_list = static_cast<NeighListKokkos<DeviceType>*>(list);
  d_numneigh = k_list->d_numneigh;
  d_neighbors = k_list->d_neighbors;
  d_ilist = k_list->d_ilist;

  special_coul[0] = force->special_coul[0];
  special_coul[1] = force->special_coul[1];
  special_coul[2] = force->special_coul[2];
  special_coul[3] = force->special_coul[3];
  qqrd2e = force->qqrd2e;

  int inum = list->inum;

  copymode = 1;

  // loop over neighbors of my atoms

  EV_FLOAT ev;

  // compute kernel A

  if (evflag) {
    if (neighflag == HALF) {
      if (newton_pair) {
        Kokkos::parallel_reduce(Kokkos::RangePolicy<DeviceType, TagPairCoulWolfKernelA<HALF,1,1> >(0,inum),*this,ev);
      } else {
        Kokkos::parallel_reduce(Kokkos::RangePolicy<DeviceType, TagPairCoulWolfKernelA<HALF,0,1> >(0,inum),*this,ev);
      }
    } else if (neighflag == HALFTHREAD) {
      if (newton_pair) {
        Kokkos::parallel_reduce(Kokkos::RangePolicy<DeviceType, TagPairCoulWolfKernelA<HALFTHREAD,1,1> >(0,inum),*this,ev);
      } else {
        Kokkos::parallel_reduce(Kokkos::RangePolicy<DeviceType, TagPairCoulWolfKernelA<HALFTHREAD,0,1> >(0,inum),*this,ev);
      }
    } else if (neighflag == FULL) {
      if (newton_pair) {
        Kokkos::parallel_reduce(Kokkos::RangePolicy<DeviceType, TagPairCoulWolfKernelA<FULL,1,1> >(0,inum),*this,ev);
      } else {
        Kokkos::parallel_reduce(Kokkos::RangePolicy<DeviceType, TagPairCoulWolfKernelA<FULL,0,1> >(0,inum),*this,ev);
      }
    }
  } else {
    if (neighflag == HALF) {
      if (newton_pair) {
        Kokkos::parallel_for(Kokkos::RangePolicy<DeviceType, TagPairCoulWolfKernelA<HALF,1,0> >(0,inum),*this);
      } else {
        Kokkos::parallel_for(Kokkos::RangePolicy<DeviceType, TagPairCoulWolfKernelA<HALF,0,0> >(0,inum),*this);
      }
    } else if (neighflag == HALFTHREAD) {
      if (newton_pair) {
        Kokkos::parallel_for(Kokkos::RangePolicy<DeviceType, TagPairCoulWolfKernelA<HALFTHREAD,1,0> >(0,inum),*this);
      } else {
        Kokkos::parallel_for(Kokkos::RangePolicy<DeviceType, TagPairCoulWolfKernelA<HALFTHREAD,0,0> >(0,inum),*this);
      }
    } else if (neighflag == FULL) {
      if (newton_pair) {
        Kokkos::parallel_for(Kokkos::RangePolicy<DeviceType, TagPairCoulWolfKernelA<FULL,1,0> >(0,inum),*this);
      } else {
        Kokkos::parallel_for(Kokkos::RangePolicy<DeviceType, TagPairCoulWolfKernelA<FULL,0,0> >(0,inum),*this);
      }
    }
  }

  if (eflag_global) eng_coul += ev.ecoul;
  if (vflag_global) {
    virial[0] += ev.v[0];
    virial[1] += ev.v[1];
    virial[2] += ev.v[2];
    virial[3] += ev.v[3];
    virial[4] += ev.v[4];
    virial[5] += ev.v[5];
  }

  if (eflag_atom) {
    k_eatom.template modify<DeviceType>();
    k_eatom.template sync<LMPHostType>();
  }

  if (vflag_atom) {
    k_vatom.template modify<DeviceType>();
    k_vatom.template sync<LMPHostType>();
  }

  if (vflag_fdotr) pair_virial_fdotr_compute(this);

  copymode = 0;
}

/* ----------------------------------------------------------------------
   init specific to this pair style
------------------------------------------------------------------------- */

template<class DeviceType>
void PairCoulWolfKokkos<DeviceType>::init_style()
{
  PairCoulWolf::init_style();

  // irequest = neigh request made by parent class

  neighflag = lmp->kokkos->neighflag;
  int irequest = neighbor->nrequest - 1;

  neighbor->requests[irequest]->
    kokkos_host = std::is_same<DeviceType,LMPHostType>::value &&
    !std::is_same<DeviceType,LMPDeviceType>::value;
  neighbor->requests[irequest]->
    kokkos_device = std::is_same<DeviceType,LMPDeviceType>::value;

  if (neighflag == FULL) {
    neighbor->requests[irequest]->full = 1;
    neighbor->requests[irequest]->half = 0;
  } else if (neighflag == HALF || neighflag == HALFTHREAD) {
    neighbor->requests[irequest]->full = 0;
    neighbor->requests[irequest]->half = 1;
  } else {
    error->all(FLERR,"Cannot use chosen neighbor list style with coul/wolf/kk");
  }
}

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

////Specialisation for Neighborlist types Half, HalfThread, Full
template<class DeviceType>
template<int NEIGHFLAG, int NEWTON_PAIR, int EVFLAG>
KOKKOS_INLINE_FUNCTION
void PairCoulWolfKokkos<DeviceType>::operator()(TagPairCoulWolfKernelA<NEIGHFLAG,NEWTON_PAIR,EVFLAG>, const int &ii, EV_FLOAT& ev) const {

  // The f array is atomic for Half/Thread neighbor style
  Kokkos::View<F_FLOAT*[3], typename DAT::t_f_array::array_layout,typename KKDevice<DeviceType>::value,Kokkos::MemoryTraits<AtomicF<NEIGHFLAG>::value> > a_f = f;
  Kokkos::View<E_FLOAT*, typename DAT::t_efloat_1d::array_layout,typename KKDevice<DeviceType>::value,Kokkos::MemoryTraits<AtomicF<NEIGHFLAG>::value> > v_eatom = k_eatom.view<DeviceType>();

  const int i = d_ilist[ii];
  const X_FLOAT xtmp = x(i,0);
  const X_FLOAT ytmp = x(i,1);
  const X_FLOAT ztmp = x(i,2);
  const F_FLOAT qtmp = q[i];

  if (eflag) {
    const F_FLOAT qisq = qtmp*qtmp;
    const F_FLOAT e_self = -(e_shift/2.0 + alf/MY_PIS) * qisq*qqrd2e;
    if (eflag_global)
      ev.ecoul += e_self;
    if (eflag_atom)
      v_eatom[i] += e_self;
  }

  //const AtomNeighborsConst d_neighbors_i = k_list.get_neighbors_const(i);
  const int jnum = d_numneigh[i];

  F_FLOAT fxtmp = 0.0;
  F_FLOAT fytmp = 0.0;
  F_FLOAT fztmp = 0.0;

  for (int jj = 0; jj < jnum; jj++) {
    //int j = d_neighbors_i(jj);
    int j = d_neighbors(i,jj);
    const F_FLOAT factor_coul = special_coul[sbmask(j)];
    j &= NEIGHMASK;
    const X_FLOAT delx = xtmp - x(j,0);
    const X_FLOAT dely = ytmp - x(j,1);
    const X_FLOAT delz = ztmp - x(j,2);
    const F_FLOAT rsq = delx*delx + dely*dely + delz*delz;

    if (rsq < cut_coulsq) {
      const F_FLOAT r = sqrt(rsq);
      const F_FLOAT prefactor = qqrd2e*qtmp*q[j]/r;
      const F_FLOAT erfcc = erfc(alf*r);
      const F_FLOAT erfcd = exp(-alf*alf*r*r);
      const F_FLOAT v_sh = (erfcc - e_shift*r) * prefactor;
      const F_FLOAT dvdrr = (erfcc/rsq + 2.0*alf/MY_PIS * erfcd/r) + f_shift;
      F_FLOAT forcecoul = dvdrr*rsq*prefactor;
      if (factor_coul < 1.0) forcecoul -= (1.0-factor_coul)*prefactor;
      const F_FLOAT fpair = forcecoul / rsq;



      fxtmp += delx*fpair;
      fytmp += dely*fpair;
      fztmp += delz*fpair;

      if ((NEIGHFLAG==HALF || NEIGHFLAG==HALFTHREAD) && (NEWTON_PAIR || j < nlocal)) {
        a_f(j,0) -= delx*fpair;
        a_f(j,1) -= dely*fpair;
        a_f(j,2) -= delz*fpair;
      }

      if (EVFLAG) {
        F_FLOAT ecoul = v_sh;
        if (eflag) {
          if (factor_coul < 1.0) ecoul -= (1.0-factor_coul)*prefactor;
          ev.ecoul += (((NEIGHFLAG==HALF || NEIGHFLAG==HALFTHREAD)&&(NEWTON_PAIR||(j<nlocal)))?1.0:0.5)*ecoul;
        }

        if (vflag_either || eflag_atom) this->template ev_tally<NEIGHFLAG,NEWTON_PAIR>(ev,i,j,ecoul,fpair,delx,dely,delz);
      }

    }
  }

  a_f(i,0) += fxtmp;
  a_f(i,1) += fytmp;
  a_f(i,2) += fztmp;
}

template<class DeviceType>
template<int NEIGHFLAG, int NEWTON_PAIR, int EVFLAG>
KOKKOS_INLINE_FUNCTION
void PairCoulWolfKokkos<DeviceType>::operator()(TagPairCoulWolfKernelA<NEIGHFLAG,NEWTON_PAIR,EVFLAG>, const int &ii) const {
  EV_FLOAT ev;
  this->template operator()<NEIGHFLAG,NEWTON_PAIR,EVFLAG>(TagPairCoulWolfKernelA<NEIGHFLAG,NEWTON_PAIR,EVFLAG>(), ii, ev);
}

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

template<class DeviceType>
template<int NEIGHFLAG, int NEWTON_PAIR>
KOKKOS_INLINE_FUNCTION
void PairCoulWolfKokkos<DeviceType>::ev_tally(EV_FLOAT &ev, const int &i, const int &j,
      const F_FLOAT &epair, const F_FLOAT &fpair, const F_FLOAT &delx,
                const F_FLOAT &dely, const F_FLOAT &delz) const
{
  const int EFLAG = eflag;
  const int VFLAG = vflag_either;

  // The eatom and vatom arrays are atomic for Half/Thread neighbor style
  Kokkos::View<E_FLOAT*, typename DAT::t_efloat_1d::array_layout,typename KKDevice<DeviceType>::value,Kokkos::MemoryTraits<AtomicF<NEIGHFLAG>::value> > v_eatom = k_eatom.view<DeviceType>();
  Kokkos::View<F_FLOAT*[6], typename DAT::t_virial_array::array_layout,typename KKDevice<DeviceType>::value,Kokkos::MemoryTraits<AtomicF<NEIGHFLAG>::value> > v_vatom = k_vatom.view<DeviceType>();

  if (EFLAG) {
    if (eflag_atom) {
      const E_FLOAT epairhalf = 0.5 * epair;
      if (NEIGHFLAG!=FULL) {
        if (NEWTON_PAIR || i < nlocal) v_eatom[i] += epairhalf;
        if (NEWTON_PAIR || j < nlocal) v_eatom[j] += epairhalf;
      } else {
        v_eatom[i] += epairhalf;
      }
    }
  }

  if (VFLAG) {
    const E_FLOAT v0 = delx*delx*fpair;
    const E_FLOAT v1 = dely*dely*fpair;
    const E_FLOAT v2 = delz*delz*fpair;
    const E_FLOAT v3 = delx*dely*fpair;
    const E_FLOAT v4 = delx*delz*fpair;
    const E_FLOAT v5 = dely*delz*fpair;

    if (vflag_global) {
      if (NEIGHFLAG!=FULL) {
        if (NEWTON_PAIR || i < nlocal) {
          ev.v[0] += 0.5*v0;
          ev.v[1] += 0.5*v1;
          ev.v[2] += 0.5*v2;
          ev.v[3] += 0.5*v3;
          ev.v[4] += 0.5*v4;
          ev.v[5] += 0.5*v5;
        }
        if (NEWTON_PAIR || j < nlocal) {
        ev.v[0] += 0.5*v0;
        ev.v[1] += 0.5*v1;
        ev.v[2] += 0.5*v2;
        ev.v[3] += 0.5*v3;
        ev.v[4] += 0.5*v4;
        ev.v[5] += 0.5*v5;
        }
      } else {
        ev.v[0] += 0.5*v0;
        ev.v[1] += 0.5*v1;
        ev.v[2] += 0.5*v2;
        ev.v[3] += 0.5*v3;
        ev.v[4] += 0.5*v4;
        ev.v[5] += 0.5*v5;
      }
    }

    if (vflag_atom) {
      if (NEIGHFLAG!=FULL) {
        if (NEWTON_PAIR || i < nlocal) {
          v_vatom(i,0) += 0.5*v0;
          v_vatom(i,1) += 0.5*v1;
          v_vatom(i,2) += 0.5*v2;
          v_vatom(i,3) += 0.5*v3;
          v_vatom(i,4) += 0.5*v4;
          v_vatom(i,5) += 0.5*v5;
        }
        if (NEWTON_PAIR || j < nlocal) {
        v_vatom(j,0) += 0.5*v0;
        v_vatom(j,1) += 0.5*v1;
        v_vatom(j,2) += 0.5*v2;
        v_vatom(j,3) += 0.5*v3;
        v_vatom(j,4) += 0.5*v4;
        v_vatom(j,5) += 0.5*v5;
        }
      } else {
        v_vatom(i,0) += 0.5*v0;
        v_vatom(i,1) += 0.5*v1;
        v_vatom(i,2) += 0.5*v2;
        v_vatom(i,3) += 0.5*v3;
        v_vatom(i,4) += 0.5*v4;
        v_vatom(i,5) += 0.5*v5;
      }
    }
  }
}

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

template<class DeviceType>
KOKKOS_INLINE_FUNCTION
int PairCoulWolfKokkos<DeviceType>::sbmask(const int& j) const {
  return j >> SBBITS & 3;
}

namespace LAMMPS_NS {
template class PairCoulWolfKokkos<LMPDeviceType>;
#ifdef KOKKOS_ENABLE_CUDA
template class PairCoulWolfKokkos<LMPHostType>;
#endif
}

