/* ----------------------------------------------------------------------
   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
   https://www.lammps.org/, Sandia National Laboratories
   LAMMPS development team: developers@lammps.org

   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 authors: Trung Dac Nguyen (ORNL), W. Michael Brown (ORNL)
------------------------------------------------------------------------- */

#include "pair_eam_gpu.h"

#include "atom.h"
#include "comm.h"
#include "domain.h"
#include "error.h"
#include "gpu_extra.h"
#include "neigh_list.h"
#include "neighbor.h"
#include "suffix.h"

#include <cmath>

using namespace LAMMPS_NS;

// External functions from cuda library for atom decomposition

int eam_gpu_init(const int ntypes, double host_cutforcesq, int **host_type2rhor,
                 int **host_type2z2r, int *host_type2frho, double ***host_rhor_spline,
                 double ***host_z2r_spline, double ***host_frho_spline, double **host_cutsq,
                 double rdr, double rdrho, double rhomax, int nrhor, int nrho, int nz2r, int nfrho,
                 int nr, const int nlocal, const int nall, const int max_nbors,
                 const int maxspecial, const double cell_size, int &gpu_mode, FILE *screen,
                 int &fp_size);
void eam_gpu_clear();
int **eam_gpu_compute_n(const int ago, const int inum_full, const int nall, double **host_x,
                        int *host_type, double *sublo, double *subhi, tagint *tag, int **nspecial,
                        tagint **special, const bool eflag, const bool vflag, const bool eatom,
                        const bool vatom, int &host_start, int **ilist, int **jnum,
                        const double cpu_time, bool &success, int &inum, void **fp_ptr);
void eam_gpu_compute(const int ago, const int inum_full, const int nlocal, const int nall,
                     double **host_x, int *host_type, int *ilist, int *numj, int **firstneigh,
                     const bool eflag, const bool vflag, const bool eatom, const bool vatom,
                     int &host_start, const double cpu_time, bool &success, void **fp_ptr);
void eam_gpu_compute_force(int *ilist, const bool eflag, const bool vflag, const bool eatom,
                           const bool vatom);
double eam_gpu_bytes();

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

PairEAMGPU::PairEAMGPU(LAMMPS *lmp) : PairEAM(lmp), gpu_mode(GPU_FORCE)
{
  respa_enable = 0;
  reinitflag = 0;
  cpu_time = 0.0;
  suffix_flag |= Suffix::GPU;
  GPU_EXTRA::gpu_ready(lmp->modify, lmp->error);
}

/* ----------------------------------------------------------------------
   check if allocated, since class can be destructed when incomplete
------------------------------------------------------------------------- */

PairEAMGPU::~PairEAMGPU()
{
  eam_gpu_clear();
}

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

double PairEAMGPU::memory_usage()
{
  double bytes = Pair::memory_usage();
  return bytes + eam_gpu_bytes();
}

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

void PairEAMGPU::compute(int eflag, int vflag)
{
  ev_init(eflag, vflag);

  // compute density on each atom on GPU

  int nlocal = atom->nlocal;
  int nall = nlocal + atom->nghost;
  int inum, host_start, inum_dev;

  bool success = true;
  int *ilist, *numneigh, **firstneigh;
  if (gpu_mode != GPU_FORCE) {
    double sublo[3], subhi[3];
    if (domain->triclinic == 0) {
      sublo[0] = domain->sublo[0];
      sublo[1] = domain->sublo[1];
      sublo[2] = domain->sublo[2];
      subhi[0] = domain->subhi[0];
      subhi[1] = domain->subhi[1];
      subhi[2] = domain->subhi[2];
    } else {
      domain->bbox(domain->sublo_lamda, domain->subhi_lamda, sublo, subhi);
    }
    inum = atom->nlocal;
    firstneigh =
        eam_gpu_compute_n(neighbor->ago, inum, nall, atom->x, atom->type, sublo, subhi, atom->tag,
                          atom->nspecial, atom->special, eflag, vflag, eflag_atom, vflag_atom,
                          host_start, &ilist, &numneigh, cpu_time, success, inum_dev, &fp_pinned);
  } else {    // gpu_mode == GPU_FORCE
    inum = list->inum;
    ilist = list->ilist;
    numneigh = list->numneigh;
    firstneigh = list->firstneigh;
    eam_gpu_compute(neighbor->ago, inum, nlocal, nall, atom->x, atom->type, ilist, numneigh,
                    firstneigh, eflag, vflag, eflag_atom, vflag_atom, host_start, cpu_time, success,
                    &fp_pinned);
  }

  if (!success) error->one(FLERR, "Insufficient memory on accelerator");

  // communicate derivative of embedding function

  comm->forward_comm(this);

  // compute forces on each atom on GPU
  if (gpu_mode != GPU_FORCE)
    eam_gpu_compute_force(nullptr, eflag, vflag, eflag_atom, vflag_atom);
  else
    eam_gpu_compute_force(ilist, eflag, vflag, eflag_atom, vflag_atom);
  if (atom->molecular != Atom::ATOMIC && neighbor->ago == 0) neighbor->build_topology();
}

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

void PairEAMGPU::init_style()
{
  // convert read-in file(s) to arrays and spline them

  file2array();
  array2spline();

  // Repeat cutsq calculation because done after call to init_style
  double maxcut = -1.0;
  double cut;
  for (int i = 1; i <= atom->ntypes; i++) {
    for (int j = i; j <= atom->ntypes; j++) {
      if (setflag[i][j] != 0 || (setflag[i][i] != 0 && setflag[j][j] != 0)) {
        cut = init_one(i, j);
        cut *= cut;
        if (cut > maxcut) maxcut = cut;
        cutsq[i][j] = cutsq[j][i] = cut;
      } else
        cutsq[i][j] = cutsq[j][i] = 0.0;
    }
  }
  double cell_size = sqrt(maxcut) + neighbor->skin;

  int maxspecial = 0;
  if (atom->molecular != Atom::ATOMIC) maxspecial = atom->maxspecial;
  int fp_size;
  int mnf = 5e-2 * neighbor->oneatom;
  int success = eam_gpu_init(atom->ntypes + 1, cutforcesq, type2rhor, type2z2r, type2frho,
                             rhor_spline, z2r_spline, frho_spline, cutsq, rdr, rdrho, rhomax, nrhor,
                             nrho, nz2r, nfrho, nr, atom->nlocal, atom->nlocal + atom->nghost, mnf,
                             maxspecial, cell_size, gpu_mode, screen, fp_size);
  GPU_EXTRA::check_flag(success, error, world);

  if (gpu_mode == GPU_FORCE) neighbor->add_request(this, NeighConst::REQ_FULL);
  fp_single = fp_size != sizeof(double);

  embedstep = -1;
}

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

double PairEAMGPU::single(int i, int j, int itype, int jtype, double rsq, double /* factor_coul */,
                          double /* factor_lj */, double &fforce)
{
  int m;
  double r, p, rhoip, rhojp, z2, z2p, recip, phi, phip, psip;
  double *coeff;

  r = sqrt(rsq);
  p = r * rdr + 1.0;
  m = static_cast<int>(p);
  m = MIN(m, nr - 1);
  p -= m;
  p = MIN(p, 1.0);

  coeff = rhor_spline[type2rhor[itype][jtype]][m];
  rhoip = (coeff[0] * p + coeff[1]) * p + coeff[2];
  coeff = rhor_spline[type2rhor[jtype][itype]][m];
  rhojp = (coeff[0] * p + coeff[1]) * p + coeff[2];
  coeff = z2r_spline[type2z2r[itype][jtype]][m];
  z2p = (coeff[0] * p + coeff[1]) * p + coeff[2];
  z2 = ((coeff[3] * p + coeff[4]) * p + coeff[5]) * p + coeff[6];

  double fp_i, fp_j;
  if (!fp_single) {
    fp_i = ((double *) fp_pinned)[i];
    fp_j = ((double *) fp_pinned)[j];
  } else {
    fp_i = ((float *) fp_pinned)[i];
    fp_j = ((float *) fp_pinned)[j];
  }

  recip = 1.0 / r;
  phi = z2 * recip;
  phip = z2p * recip - phi * recip;
  psip = fp_i * rhojp + fp_j * rhoip + phip;
  fforce = -psip * recip;

  return phi;
}

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

int PairEAMGPU::pack_forward_comm(int n, int *list, double *buf, int /* pbc_flag */,
                                  int * /* pbc */)
{
  int i, j, m;

  m = 0;

  if (fp_single) {
    auto *fp_ptr = (float *) fp_pinned;
    for (i = 0; i < n; i++) {
      j = list[i];
      buf[m++] = static_cast<double>(fp_ptr[j]);
    }
  } else {
    auto *fp_ptr = (double *) fp_pinned;
    for (i = 0; i < n; i++) {
      j = list[i];
      buf[m++] = fp_ptr[j];
    }
  }

  return m;
}

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

void PairEAMGPU::unpack_forward_comm(int n, int first, double *buf)
{
  int i, m, last;

  m = 0;
  last = first + n;
  if (fp_single) {
    auto *fp_ptr = (float *) fp_pinned;
    for (i = first; i < last; i++) fp_ptr[i] = buf[m++];
  } else {
    auto *fp_ptr = (double *) fp_pinned;
    for (i = first; i < last; i++) fp_ptr[i] = buf[m++];
  }
}
