/* ----------------------------------------------------------------------
   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 author: Mike Brown (SNL)
------------------------------------------------------------------------- */

#include "pair_resquared_gpu.h"

#include "atom.h"
#include "atom_vec_ellipsoid.h"
#include "domain.h"
#include "error.h"
#include "force.h"
#include "gpu_extra.h"
#include "math_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 re_gpu_init(const int ntypes, double **shape, double **well, double **cutsq,
                double **sigma, double **epsilon, int **form,
                double **host_lj1, double **host_lj2, double **host_lj3,
                double **host_lj4, double **offset, double *special_lj,
                const int nlocal, const int nall, const int max_nbors,
                const int maxspecial, const double cell_size, int &gpu_mode,
                FILE *screen);
void re_gpu_clear();
int **re_gpu_compute_n(const int ago, const int inum, 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, const int *ellipsoid,
                       const void *bonus);
int *re_gpu_compute(const int ago, const int inum, 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, const int *ellipsoid,
                    const void *bonus);
double re_gpu_bytes();

enum { SPHERE_SPHERE, SPHERE_ELLIPSE, ELLIPSE_SPHERE, ELLIPSE_ELLIPSE };

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

PairRESquaredGPU::PairRESquaredGPU(LAMMPS *lmp) : PairRESquared(lmp), gpu_mode(GPU_FORCE)
{
  reinitflag = 0;
  avec = dynamic_cast<AtomVecEllipsoid *>(atom->style_match("ellipsoid"));
  if (!avec) error->all(FLERR, "Pair resquared/gpu requires atom style ellipsoid");
  suffix_flag |= Suffix::GPU;
  GPU_EXTRA::gpu_ready(lmp->modify, lmp->error);
}

/* ----------------------------------------------------------------------
   free all arrays
------------------------------------------------------------------------- */

PairRESquaredGPU::~PairRESquaredGPU()
{
  re_gpu_clear();
  cpu_time = 0.0;
}

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

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

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

  bool success = true;
  int *ilist, *numneigh, **firstneigh;

  AtomVecEllipsoid::Bonus *bonus = avec->bonus;
  int *ellipsoid = atom->ellipsoid;

  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 =
        re_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, ellipsoid,
                         bonus);
  } else {
    inum = list->inum;
    numneigh = list->numneigh;
    firstneigh = list->firstneigh;
    ilist = re_gpu_compute(neighbor->ago, inum, nall, atom->x, atom->type,
                           list->ilist, numneigh, firstneigh, eflag, vflag,
                           eflag_atom, vflag_atom, host_start, cpu_time,
                           success, ellipsoid, bonus);
  }
  if (!success) error->one(FLERR, "Insufficient memory on accelerator");

  if (atom->molecular != Atom::ATOMIC && neighbor->ago == 0)
    neighbor->build_topology();
  if (host_start < inum) {
    cpu_time = platform::walltime();
    cpu_compute(host_start, inum, eflag, vflag, ilist, numneigh, firstneigh);
    cpu_time = platform::walltime() - cpu_time;
  }
}

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

void PairRESquaredGPU::init_style()
{
  if (!atom->ellipsoid_flag) error->all(FLERR, "Pair resquared/gpu requires atom style ellipsoid");

  // per-type shape precalculations
  // require that atom shapes are identical within each type
  // if shape = 0 for point particle, set shape = 1 as required by Gay-Berne

  for (int i = 1; i <= atom->ntypes; i++) {
    if (!atom->shape_consistency(i, shape1[i][0], shape1[i][1], shape1[i][2]))
      error->all(FLERR, "Pair resquared/gpu requires atoms with same type have same shape");
    if (setwell[i]) {
      shape2[i][0] = shape1[i][0] * shape1[i][0];
      shape2[i][1] = shape1[i][1] * shape1[i][1];
      shape2[i][2] = shape1[i][2] * shape1[i][2];
      lshape[i] = shape1[i][0] * shape1[i][1] * shape1[i][2];
    }
  }

  // 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 mnf = 5e-2 * neighbor->oneatom;
  int success =
      re_gpu_init(atom->ntypes + 1, shape1, well, cutsq, sigma, epsilon, form,
                  lj1, lj2, lj3, lj4, offset, force->special_lj, atom->nlocal,
                  atom->nlocal + atom->nghost, mnf, maxspecial, cell_size,
                  gpu_mode, screen);
  GPU_EXTRA::check_flag(success, error, world);

  if (gpu_mode == GPU_FORCE) neighbor->add_request(this, NeighConst::REQ_FULL);
}

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

double PairRESquaredGPU::memory_usage()
{
  double bytes = Pair::memory_usage();
  return bytes + re_gpu_bytes();
}

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

void PairRESquaredGPU::cpu_compute(int start, int inum, int eflag, int /* vflag */, int *ilist,
                                   int *numneigh, int **firstneigh)
{
  int i, j, ii, jj, jnum, itype, jtype;
  double evdwl, one_eng, rsq, r2inv, r6inv, forcelj, factor_lj;
  double fforce[3], ttor[3], rtor[3], r12[3];
  int *jlist;
  RE2Vars wi, wj;

  double **x = atom->x;
  double **f = atom->f;
  double **tor = atom->torque;
  int *type = atom->type;
  double *special_lj = force->special_lj;

  // loop over neighbors of my atoms

  for (ii = start; ii < inum; ii++) {
    i = ilist[ii];
    itype = type[i];

    // not a LJ sphere

    if (lshape[itype] != 0.0) precompute_i(i, wi);

    jlist = firstneigh[i];
    jnum = numneigh[i];

    for (jj = 0; jj < jnum; jj++) {
      j = jlist[jj];
      factor_lj = special_lj[sbmask(j)];
      j &= NEIGHMASK;

      // r12 = center to center vector

      r12[0] = x[j][0] - x[i][0];
      r12[1] = x[j][1] - x[i][1];
      r12[2] = x[j][2] - x[i][2];
      rsq = MathExtra::dot3(r12, r12);
      jtype = type[j];

      // compute if less than cutoff

      if (rsq < cutsq[itype][jtype]) {
        switch (form[itype][jtype]) {

          case SPHERE_SPHERE:
            r2inv = 1.0 / rsq;
            r6inv = r2inv * r2inv * r2inv;
            forcelj = r6inv * (lj1[itype][jtype] * r6inv - lj2[itype][jtype]);
            forcelj *= -r2inv;
            if (eflag)
              one_eng =
                  r6inv * (r6inv * lj3[itype][jtype] - lj4[itype][jtype]) - offset[itype][jtype];
            fforce[0] = r12[0] * forcelj;
            fforce[1] = r12[1] * forcelj;
            fforce[2] = r12[2] * forcelj;
            break;

          case SPHERE_ELLIPSE:
            precompute_i(j, wj);
            one_eng = resquared_lj(j, i, wj, r12, rsq, fforce, rtor, false);
            break;

          case ELLIPSE_SPHERE:
            one_eng = resquared_lj(i, j, wi, r12, rsq, fforce, ttor, true);
            tor[i][0] += ttor[0] * factor_lj;
            tor[i][1] += ttor[1] * factor_lj;
            tor[i][2] += ttor[2] * factor_lj;
            break;

          default:
            precompute_i(j, wj);
            one_eng = resquared_analytic(i, j, wi, wj, r12, rsq, fforce, ttor, rtor);
            tor[i][0] += ttor[0] * factor_lj;
            tor[i][1] += ttor[1] * factor_lj;
            tor[i][2] += ttor[2] * factor_lj;

            break;
        }

        fforce[0] *= factor_lj;
        fforce[1] *= factor_lj;
        fforce[2] *= factor_lj;
        f[i][0] += fforce[0];
        f[i][1] += fforce[1];
        f[i][2] += fforce[2];

        if (eflag) evdwl = factor_lj * one_eng;

        if (evflag)
          ev_tally_xyz_full(i, evdwl, 0.0, fforce[0], fforce[1], fforce[2], -r12[0], -r12[1],
                            -r12[2]);
      }
    }
  }
}
