// **************************************************************************
//                                coul_debye.cu
//                             -------------------
//                               Trung Dac Nguyen
//
//  Device code for acceleration of the coul/debye pair style
//
// __________________________________________________________________________
//    This file is part of the LAMMPS Accelerator Library (LAMMPS_AL)
// __________________________________________________________________________
//
//    begin                :
//    email                : ndtrung@umich.edu
// ***************************************************************************

#if defined(NV_KERNEL) || defined(USE_HIP)

#include "lal_aux_fun1.h"
#ifndef _DOUBLE_DOUBLE
_texture( pos_tex,float4);
_texture( q_tex,float);
#else
_texture_2d( pos_tex,int4);
_texture( q_tex,int2);
#endif

#else
#define pos_tex x_
#define q_tex q_
#endif

__kernel void k_coul_debye(const __global numtyp4 *restrict x_,
                           const __global numtyp *restrict scale,
                           const int lj_types,
                           const __global numtyp *restrict sp_cl_in,
                           const __global int *dev_nbor,
                           const __global int *dev_packed,
                           __global acctyp4 *restrict ans,
                           __global acctyp *restrict engv,
                           const int eflag, const int vflag, const int inum,
                           const int nbor_pitch,
                           const __global numtyp *restrict q_ ,
                           const __global numtyp *restrict cutsq,
                           const numtyp qqrd2e, const numtyp kappa,
                           const int t_per_atom) {
  int tid, ii, offset;
  atom_info(t_per_atom,ii,tid,offset);

  __local numtyp sp_cl[4];
  sp_cl[0]=sp_cl_in[0];
  sp_cl[1]=sp_cl_in[1];
  sp_cl[2]=sp_cl_in[2];
  sp_cl[3]=sp_cl_in[3];

  acctyp energy=(acctyp)0;
  acctyp e_coul=(acctyp)0;
  acctyp4 f;
  f.x=(acctyp)0; f.y=(acctyp)0; f.z=(acctyp)0;
  acctyp virial[6];
  for (int i=0; i<6; i++)
    virial[i]=(acctyp)0;

  if (ii<inum) {
    int i, numj, nbor, nbor_end;
    __local int n_stride;
    nbor_info(dev_nbor,dev_packed,nbor_pitch,t_per_atom,ii,offset,i,numj,
              n_stride,nbor_end,nbor);

    numtyp4 ix; fetch4(ix,i,pos_tex); //x_[i];
    numtyp qtmp; fetch(qtmp,i,q_tex);
    int itype=ix.w;

    numtyp factor_coul;
    for ( ; nbor<nbor_end; nbor+=n_stride) {

      int j=dev_packed[nbor];
      factor_coul = sp_cl[sbmask(j)];
      j &= NEIGHMASK;

      numtyp4 jx; fetch4(jx,j,pos_tex); //x_[j];
      int jtype=jx.w;

      // Compute r12
      numtyp delx = ix.x-jx.x;
      numtyp dely = ix.y-jx.y;
      numtyp delz = ix.z-jx.z;
      numtyp rsq = delx*delx+dely*dely+delz*delz;

      int mtype=itype*lj_types+jtype;
      if (rsq<cutsq[mtype]) {
        numtyp r2inv=ucl_recip(rsq);
        numtyp forcecoul, force, r, rinv, screening;

        r = ucl_sqrt(rsq);
        rinv = ucl_recip(r);
        fetch(screening,j,q_tex);
        screening *= ucl_exp(-kappa*r);
        forcecoul = qqrd2e*qtmp*scale[mtype]*(kappa+rinv)*screening*factor_coul;
        force = forcecoul * r2inv;

        f.x+=delx*force;
        f.y+=dely*force;
        f.z+=delz*force;

        if (eflag>0) {
          e_coul+=qqrd2e*scale[mtype]*qtmp*rinv*screening*factor_coul;
        }
        if (vflag>0) {
          virial[0] += delx*delx*force;
          virial[1] += dely*dely*force;
          virial[2] += delz*delz*force;
          virial[3] += delx*dely*force;
          virial[4] += delx*delz*force;
          virial[5] += dely*delz*force;
        }
      }

    } // for nbor
    store_answers_q(f,energy,e_coul,virial,ii,inum,tid,t_per_atom,offset,eflag,
                    vflag,ans,engv);
  } // if ii
}

__kernel void k_coul_debye_fast(const __global numtyp4 *restrict x_,
                                const __global numtyp *restrict scale_in,
                                const __global numtyp *restrict sp_cl_in,
                                const __global int *dev_nbor,
                                const __global int *dev_packed,
                                __global acctyp4 *restrict ans,
                                __global acctyp *restrict engv,
                                const int eflag, const int vflag, const int inum,
                                const int nbor_pitch,
                                const __global numtyp *restrict q_,
                                const __global numtyp *restrict _cutsq,
                                const numtyp qqrd2e, const numtyp kappa,
                                const int t_per_atom) {
  int tid, ii, offset;
  atom_info(t_per_atom,ii,tid,offset);

  __local numtyp scale[MAX_SHARED_TYPES*MAX_SHARED_TYPES];
  __local numtyp cutsq[MAX_SHARED_TYPES*MAX_SHARED_TYPES];
  __local numtyp sp_cl[4];
  if (tid<4)
    sp_cl[tid]=sp_cl_in[tid];
  if (tid<MAX_SHARED_TYPES*MAX_SHARED_TYPES) {
    scale[tid]=scale_in[tid];
    cutsq[tid]=_cutsq[tid];
  }

  acctyp energy=(acctyp)0;
  acctyp e_coul=(acctyp)0;
  acctyp4 f;
  f.x=(acctyp)0; f.y=(acctyp)0; f.z=(acctyp)0;
  acctyp virial[6];
  for (int i=0; i<6; i++)
    virial[i]=(acctyp)0;

  __syncthreads();

  if (ii<inum) {
    int i, numj, nbor, nbor_end;
    __local int n_stride;
    nbor_info(dev_nbor,dev_packed,nbor_pitch,t_per_atom,ii,offset,i,numj,
              n_stride,nbor_end,nbor);

    numtyp4 ix; fetch4(ix,i,pos_tex); //x_[i];
    numtyp qtmp; fetch(qtmp,i,q_tex);
    int iw=ix.w;
    int itype=fast_mul((int)MAX_SHARED_TYPES,iw);

    numtyp factor_coul;
    for ( ; nbor<nbor_end; nbor+=n_stride) {

      int j=dev_packed[nbor];
      factor_coul = sp_cl[sbmask(j)];
      j &= NEIGHMASK;

      numtyp4 jx; fetch4(jx,j,pos_tex); //x_[j];
      int mtype=itype+jx.w;

      // Compute r12
      numtyp delx = ix.x-jx.x;
      numtyp dely = ix.y-jx.y;
      numtyp delz = ix.z-jx.z;
      numtyp rsq = delx*delx+dely*dely+delz*delz;

      if (rsq<cutsq[mtype]) {
        numtyp r2inv=ucl_recip(rsq);
        numtyp forcecoul, force, r, rinv, screening;

        r = ucl_sqrt(rsq);
        rinv = ucl_recip(r);
        fetch(screening,j,q_tex);
        screening *= ucl_exp(-kappa*r);
        forcecoul = qqrd2e*scale[mtype]*qtmp*(kappa+rinv)*screening*factor_coul;
        force = forcecoul * r2inv;

        f.x+=delx*force;
        f.y+=dely*force;
        f.z+=delz*force;

        if (eflag>0) {
          e_coul+=qqrd2e*scale[mtype]*qtmp*rinv*screening*factor_coul;
        }
        if (vflag>0) {
          virial[0] += delx*delx*force;
          virial[1] += dely*dely*force;
          virial[2] += delz*delz*force;
          virial[3] += delx*dely*force;
          virial[4] += delx*delz*force;
          virial[5] += dely*delz*force;
        }
      }

    } // for nbor
    store_answers_q(f,energy,e_coul,virial,ii,inum,tid,t_per_atom,offset,eflag,
                    vflag,ans,engv);
  } // if ii
}

