src/gromacs/mdlib/nbnxn_ocl/nbnxn_ocl_kernel_nvidia.clh

   1 /*
   2  * This file is part of the GROMACS molecular simulation package.
   3  *
   4  * Copyright (c) 2012,2013,2014,2016, by the GROMACS development team, led by
   5  * Mark Abraham, David van der Spoel, Berk Hess, and Erik Lindahl,
   6  * and including many others, as listed in the AUTHORS file in the
   7  * top-level source directory and at http://www.gromacs.org.
   8  *
   9  * GROMACS is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public License
  11  * as published by the Free Software Foundation; either version 2.1
  12  * of the License, or (at your option) any later version.
  13  *
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  35
  36 /*! \internal \file
  37  *  \brief OpenCL non-bonded kernel for NVIDIA GPUs.
  38  *
  39  *  OpenCL 1.2 support is expected (CUDA driver API 7.5 and later).
  40  *
  41  *  \author Anca Hamuraru <anca@streamcomputing.eu>
  42  *  \author Szilárd Páll <pall.szilard@gmail.com>
  43  *  \ingroup module_mdlib
  44  */
  45
  46
  47 #include "nbnxn_ocl_kernel_utils.clh"
  48
  49 /////////////////////////////////////////////////////////////////////////////////////////////////
  50
  51 #if defined EL_EWALD_ANA || defined EL_EWALD_TAB
  52 /* Note: convenience macro, needs to be undef-ed at the end of the file. */
  53 #define EL_EWALD_ANY
  54 #endif
  55
  56 #if defined EL_EWALD_ANY || defined EL_RF || defined LJ_EWALD || (defined EL_CUTOFF && defined CALC_ENERGIES)
  57 /* Macro to control the calculation of exclusion forces in the kernel
  58  * We do that with Ewald (elec/vdw) and RF. Cut-off only has exclusion
  59  * energy terms.
  60  *
  61  * Note: convenience macro, needs to be undef-ed at the end of the file.
  62  */
  63 #define EXCLUSION_FORCES
  64 #endif
  65
  66 #if defined LJ_EWALD_COMB_GEOM || defined LJ_EWALD_COMB_LB
  67 /* Note: convenience macro, needs to be undef-ed at the end of the file. */
  68 #define LJ_EWALD
  69 #endif
  70
  71 #if defined LJ_COMB_GEOM || defined LJ_COMB_LB
  72 /* Note: convenience macro, needs to be undef-ed at the end of the file. */
  73 #define LJ_COMB
  74 #endif
  75
  76 /*
  77    Kernel launch parameters:
  78     - #blocks   = #pair lists, blockId = pair list Id
  79     - #threads  = CL_SIZE^2
  80     - shmem     = CL_SIZE^2 * sizeof(float)
  81
  82     Each thread calculates an i force-component taking one pair of i-j atoms.
  83  */
  84
  85 /* NOTE:
  86  NB_KERNEL_FUNC_NAME differs from the CUDA equivalent as it is not a variadic macro due to OpenCL not having a support for them, this version only takes exactly 2 arguments.
  87  Thus if more strings need to be appended a new macro must be written or it must be directly appended here.
  88 */
  89 __attribute__((reqd_work_group_size(CL_SIZE, CL_SIZE, 1)))
  90 #ifdef PRUNE_NBL
  91     #ifdef CALC_ENERGIES
  92         __kernel void NB_KERNEL_FUNC_NAME(nbnxn_kernel, _VF_prune_opencl)
  93     #else
  94         __kernel void NB_KERNEL_FUNC_NAME(nbnxn_kernel, _F_prune_opencl)
  95     #endif
  96 #else
  97     #ifdef CALC_ENERGIES
  98         __kernel void NB_KERNEL_FUNC_NAME(nbnxn_kernel, _VF_opencl)
  99     #else
 100         __kernel void NB_KERNEL_FUNC_NAME(nbnxn_kernel, _F_opencl)
 101     #endif
 102 #endif
 103 (
 104 #ifndef LJ_COMB
 105  int ntypes,                                                               /* IN  */
 106 #endif
 107  cl_nbparam_params_t nbparam_params,                                       /* IN  */
 108  const __global float4 *restrict xq,                                       /* IN  */
 109  __global float *restrict f,                /* stores float3 values */     /* OUT */
 110  __global float *restrict e_lj,                                            /* OUT */
 111  __global float *restrict e_el,                                            /* OUT */
 112 __global float *restrict fshift,            /* stores float3 values */     /* OUT */
 113 #ifdef LJ_COMB
 114  const __global float2 *restrict lj_comb,      /* stores float2 values */  /* IN  */
 115 #else
 116  const __global int *restrict atom_types,                                  /* IN  */
 117 #endif
 118  const __global float *restrict shift_vec,  /* stores float3 values */     /* IN  */
 119  __constant float* nbfp_climg2d,                                           /* IN  */
 120  __constant float* nbfp_comb_climg2d,                                      /* IN  */
 121  __constant float* coulomb_tab_climg2d,                                    /* IN  */
 122  const __global nbnxn_sci_t* pl_sci,                                       /* IN  */
 123 #ifndef PRUNE_NBL
 124     const
 125 #endif
 126  __global nbnxn_cj4_t* pl_cj4,                                             /* OUT / IN */
 127  const __global nbnxn_excl_t* excl,                                        /* IN  */
 128  int bCalcFshift,                                                          /* IN  */
 129  __local  float4   *xqib,                                                  /* Pointer to dyn alloc'ed shmem */
 130  __global float *debug_buffer                                              /* Debug buffer, can be used with print_to_debug_buffer_f */
 131  )
 132 {
 133     /* convenience variables */
 134     cl_nbparam_params_t *nbparam = &nbparam_params;
 135
 136     float               rcoulomb_sq = nbparam->rcoulomb_sq;
 137 #ifdef LJ_COMB
 138     float2              ljcp_i, ljcp_j;
 139 #endif
 140 #ifdef VDW_CUTOFF_CHECK
 141     float               rvdw_sq     = nbparam_params.rvdw_sq;
 142     float               vdw_in_range;
 143 #endif
 144 #ifdef LJ_EWALD
 145     float               lje_coeff2, lje_coeff6_6;
 146 #endif
 147 #ifdef EL_RF
 148     float two_k_rf              = nbparam->two_k_rf;
 149 #endif
 150 #ifdef EL_EWALD_TAB
 151     float coulomb_tab_scale     = nbparam->coulomb_tab_scale;
 152 #endif
 153 #ifdef EL_EWALD_ANA
 154     float beta2                 = nbparam->ewald_beta*nbparam->ewald_beta;
 155     float beta3                 = nbparam->ewald_beta*nbparam->ewald_beta*nbparam->ewald_beta;
 156 #endif
 157 #ifdef PRUNE_NBL
 158     float rlist_sq              = nbparam->rlist_sq;
 159 #endif
 160
 161 #ifdef CALC_ENERGIES
 162 #ifdef EL_EWALD_ANY
 163     float  beta        = nbparam->ewald_beta;
 164     float  ewald_shift = nbparam->sh_ewald;
 165 #else
 166     float  c_rf        = nbparam->c_rf;
 167 #endif /* EL_EWALD_ANY */
 168 #endif /* CALC_ENERGIES */
 169
 170     /* thread/block/warp id-s */
 171     unsigned int tidxi  = get_local_id(0);
 172     unsigned int tidxj  = get_local_id(1);
 173     unsigned int tidx   = get_local_id(1) * get_local_size(0) + get_local_id(0);
 174     unsigned int bidx   = get_group_id(0);
 175     unsigned int widx   = tidx / WARP_SIZE; /* warp index */
 176     int          sci, ci, cj, ci_offset,
 177                  ai, aj,
 178                  cij4_start, cij4_end;
 179 #ifndef LJ_COMB
 180     int          typei, typej;
 181 #endif
 182     int          i, jm, j4, wexcl_idx;
 183     float        qi, qj_f,
 184                  r2, inv_r, inv_r2;
 185 #if !defined LJ_COMB_LB || defined CALC_ENERGIES
 186     float        inv_r6, c6, c12;
 187 #endif
 188 #if defined LJ_COMB_LB
 189     float        sigma, epsilon;
 190 #endif
 191     float        int_bit,
 192                  F_invr;
 193
 194 #ifdef CALC_ENERGIES
 195     float        E_lj, E_el;
 196 #endif
 197 #if defined CALC_ENERGIES || defined LJ_POT_SWITCH
 198     float        E_lj_p;
 199 #endif
 200     unsigned int wexcl, imask, mask_ji;
 201     float4       xqbuf;
 202     float3       xi, xj, rv, f_ij, fcj_buf/*, fshift_buf*/;
 203     float        fshift_buf;
 204     float3       fci_buf[NCL_PER_SUPERCL]; /* i force buffer */
 205     nbnxn_sci_t  nb_sci;
 206
 207     /*! i-cluster interaction mask for a super-cluster with all NCL_PER_SUPERCL=8 bits set */
 208     const unsigned superClInteractionMask = ((1U << NCL_PER_SUPERCL) - 1U);
 209
 210     /* shmem buffer for cj, for both warps separately */
 211     __local int *cjs       = (__local int *)(xqib + NCL_PER_SUPERCL * CL_SIZE);
 212     #define LOCAL_OFFSET cjs + 2 * NBNXN_GPU_JGROUP_SIZE
 213
 214 #ifdef IATYPE_SHMEM
 215 #ifndef LJ_COMB
 216     /* shmem buffer for i atom-type pre-loading */
 217     __local int *atib      = (__local int *)(LOCAL_OFFSET);
 218     #undef LOCAL_OFFSET
 219     #define LOCAL_OFFSET atib + NCL_PER_SUPERCL * CL_SIZE
 220 #else
 221     __local float2 *ljcpib = (__local float2 *)(LOCAL_OFFSET);
 222     #undef LOCAL_OFFSET
 223     #define LOCAL_OFFSET ljcpib + NCL_PER_SUPERCL * CL_SIZE
 224 #endif
 225 #endif
 226
 227 #ifndef REDUCE_SHUFFLE
 228     /* shmem j force buffer */
 229     __local float *f_buf   = (__local float *)(LOCAL_OFFSET);
 230     #undef LOCAL_OFFSET
 231     #define LOCAL_OFFSET f_buf + CL_SIZE * CL_SIZE * 3
 232 #endif
 233     /* Local buffer used to implement __any warp vote function from CUDA.
 234        volatile is used to avoid compiler optimizations for AMD builds. */
 235     volatile __local uint *warp_any = (__local uint*)(LOCAL_OFFSET);
 236 #undef LOCAL_OFFSET
 237
 238     nb_sci      = pl_sci[bidx];         /* my i super-cluster's index = current bidx */
 239     sci         = nb_sci.sci;           /* super-cluster */
 240     cij4_start  = nb_sci.cj4_ind_start; /* first ...*/
 241     cij4_end    = nb_sci.cj4_ind_end;   /* and last index of j clusters */
 242
 243     /* Pre-load i-atom x and q into shared memory */
 244     ci = sci * NCL_PER_SUPERCL + tidxj;
 245     ai = ci * CL_SIZE + tidxi;
 246
 247     xqbuf    = xq[ai] + (float4)(shift_vec[3 * nb_sci.shift], shift_vec[3 * nb_sci.shift + 1], shift_vec[3 * nb_sci.shift + 2], 0.0f);
 248     xqbuf.w *= nbparam->epsfac;
 249     xqib[tidxj * CL_SIZE + tidxi] = xqbuf;
 250
 251 #ifdef IATYPE_SHMEM
 252 #ifndef LJ_COMB
 253     /* Pre-load the i-atom types into shared memory */
 254     atib[tidxj * CL_SIZE + tidxi]   = atom_types[ai];
 255 #else
 256     ljcpib[tidxj * CL_SIZE + tidxi] = lj_comb[ai];
 257 #endif
 258 #endif
 259     /* Initialise warp vote. (8x8 block) 2 warps for nvidia */
 260     if(tidx==0 || tidx==32)
 261         warp_any[widx] = 0;
 262
 263     barrier(CLK_LOCAL_MEM_FENCE);
 264
 265     for (ci_offset = 0; ci_offset < NCL_PER_SUPERCL; ci_offset++)
 266     {
 267         fci_buf[ci_offset] = (float3)(0.0f);
 268     }
 269
 270 #ifdef LJ_EWALD
 271     /* TODO: we are trading registers with flops by keeping lje_coeff-s, try re-calculating it later */
 272     lje_coeff2   = nbparam->ewaldcoeff_lj*nbparam->ewaldcoeff_lj;
 273     lje_coeff6_6 = lje_coeff2*lje_coeff2*lje_coeff2*ONE_SIXTH_F;
 274 #endif /* LJ_EWALD */
 275
 276
 277 #ifdef CALC_ENERGIES
 278     E_lj = 0.0f;
 279     E_el = 0.0f;
 280
 281 #if defined EXCLUSION_FORCES /* Ewald or RF */
 282     if (nb_sci.shift == CENTRAL && pl_cj4[cij4_start].cj[0] == sci*NCL_PER_SUPERCL)
 283     {
 284         /* we have the diagonal: add the charge and LJ self interaction energy term */
 285         for (i = 0; i < NCL_PER_SUPERCL; i++)
 286         {
 287 #if defined EL_EWALD_ANY || defined EL_RF || defined EL_CUTOFF
 288             qi    = xqib[i * CL_SIZE + tidxi].w;
 289             E_el += qi*qi;
 290 #endif
 291 #if defined LJ_EWALD
 292             E_lj += nbfp_climg2d[atom_types[(sci*NCL_PER_SUPERCL + i)*CL_SIZE + tidxi]*(ntypes + 1)*2];
 293 #endif /* LJ_EWALD */
 294         }
 295
 296         /* divide the self term(s) equally over the j-threads, then multiply with the coefficients. */
 297 #ifdef LJ_EWALD
 298         E_lj /= CL_SIZE;
 299         E_lj *= 0.5f*ONE_SIXTH_F*lje_coeff6_6;
 300 #endif  /* LJ_EWALD */
 301
 302 #if defined EL_EWALD_ANY || defined EL_RF || defined EL_CUTOFF
 303         /* Correct for epsfac^2 due to adding qi^2 */
 304         E_el /= nbparam->epsfac*CL_SIZE;
 305 #if defined EL_RF || defined EL_CUTOFF
 306         E_el *= -0.5f*c_rf;
 307 #else
 308         E_el *= -beta*M_FLOAT_1_SQRTPI; /* last factor 1/sqrt(pi) */
 309 #endif
 310 #endif                                  /* EL_EWALD_ANY || defined EL_RF || defined EL_CUTOFF */
 311     }
 312 #endif                                  /* EXCLUSION_FORCES */
 313
 314 #endif                                  /* CALC_ENERGIES */
 315
 316     /* loop over the j clusters = seen by any of the atoms in the current super-cluster */
 317     for (j4 = cij4_start; j4 < cij4_end; j4++)
 318     {
 319         wexcl_idx   = pl_cj4[j4].imei[widx].excl_ind;
 320         imask       = pl_cj4[j4].imei[widx].imask;
 321         wexcl       = excl[wexcl_idx].pair[(tidx) & (WARP_SIZE - 1)];
 322
 323 #ifndef PRUNE_NBL
 324         if (imask)
 325 #endif
 326         {
 327             /* Pre-load cj into shared memory on both warps separately */
 328             if ((tidxj == 0 || tidxj == 4) && tidxi < NBNXN_GPU_JGROUP_SIZE)
 329             {
 330                 cjs[tidxi + tidxj * NBNXN_GPU_JGROUP_SIZE / 4] = pl_cj4[j4].cj[tidxi];
 331             }
 332
 333             /* TODO: check loop unrolling with NVIDIA OpenCL */
 334 #if !defined PRUNE_NBL
 335 //#pragma unroll 4
 336 #endif
 337
 338             for (jm = 0; jm < NBNXN_GPU_JGROUP_SIZE; jm++)
 339             {
 340                 if (imask & (superClInteractionMask << (jm * NCL_PER_SUPERCL)))
 341                 {
 342                     mask_ji = (1U << (jm * NCL_PER_SUPERCL));
 343
 344                     cj      = cjs[jm + (tidxj & 4) * NBNXN_GPU_JGROUP_SIZE / 4];
 345                     aj      = cj * CL_SIZE + tidxj;
 346
 347                     /* load j atom data */
 348                     xqbuf   = xq[aj];
 349                     xj      = (float3)(xqbuf.xyz);
 350                     qj_f    = xqbuf.w;
 351 #ifndef LJ_COMB
 352                     typej   = atom_types[aj];
 353 #else
 354                     ljcp_j  = lj_comb[aj];
 355 #endif
 356
 357                     fcj_buf = (float3)(0.0f);
 358
 359 #if !defined PRUNE_NBL
 360 #pragma unroll 8
 361 #endif
 362                     for (i = 0; i < NCL_PER_SUPERCL; i++)
 363                     {
 364                         if (imask & mask_ji)
 365                         {
 366                             ci_offset   = i;                     /* i force buffer offset */
 367
 368                             ci      = sci * NCL_PER_SUPERCL + i; /* i cluster index */
 369                             ai      = ci * CL_SIZE + tidxi;      /* i atom index */
 370
 371                             /* all threads load an atom from i cluster ci into shmem! */
 372                             xqbuf   = xqib[i * CL_SIZE + tidxi];
 373                             xi      = (float3)(xqbuf.xyz);
 374
 375                             /* distance between i and j atoms */
 376                             rv      = xi - xj;
 377                             r2      = norm2(rv);
 378
 379 #ifdef PRUNE_NBL
 380                             /* vote.. should code shmem serialisation, wonder what the hit will be */
 381                             if (r2 < rlist_sq)
 382                                 warp_any[widx]=1;
 383
 384                             /* If _none_ of the atoms pairs are in cutoff range,
 385                                the bit corresponding to the current
 386                                cluster-pair in imask gets set to 0. */
 387                             if (!warp_any[widx])
 388                                 imask &= ~mask_ji;
 389
 390                             warp_any[widx]=0;
 391 #endif
 392
 393                             int_bit = (wexcl & mask_ji) ? 1.0f : 0.0f;
 394
 395                             /* cutoff & exclusion check */
 396 #ifdef EXCLUSION_FORCES
 397                             if (r2 < rcoulomb_sq *
 398                                 (nb_sci.shift != CENTRAL || ci != cj || tidxj > tidxi))
 399 #else
 400                             if (r2 < rcoulomb_sq * int_bit)
 401 #endif
 402                             {
 403                                 /* load the rest of the i-atom parameters */
 404                                 qi      = xqbuf.w;
 405 #ifdef IATYPE_SHMEM
 406 #ifndef LJ_COMB
 407                                 typei   = atib[i * CL_SIZE + tidxi];
 408 #else
 409                                 ljcp_i  = ljcpib[i * CL_SIZE + tidxi];
 410 #endif
 411 #else /* IATYPE_SHMEM */
 412 #ifndef LJ_COMB
 413                                 typei   = atom_types[ai];
 414 #else
 415                                 ljcp_i  = lj_comb[ai];
 416 #endif
 417 #endif /* IATYPE_SHMEM */
 418                                 /* LJ 6*C6 and 12*C12 */
 419 #ifndef LJ_COMB
 420                                 c6      = nbfp_climg2d[2 * (ntypes * typei + typej)];
 421                                 c12     = nbfp_climg2d[2 * (ntypes * typei + typej)+1];
 422 #else   /* LJ_COMB */
 423 #ifdef LJ_COMB_GEOM
 424                                 c6      = ljcp_i.x * ljcp_j.x;
 425                                 c12     = ljcp_i.y * ljcp_j.y;
 426 #else
 427                                 /* LJ 2^(1/6)*sigma and 12*epsilon */
 428                                 sigma   = ljcp_i.x + ljcp_j.x;
 429                                 epsilon = ljcp_i.y * ljcp_j.y;
 430 #if defined CALC_ENERGIES || defined LJ_FORCE_SWITCH || defined LJ_POT_SWITCH
 431                                 convert_sigma_epsilon_to_c6_c12(sigma, epsilon, &c6, &c12);
 432 #endif
 433 #endif                          /* LJ_COMB_GEOM */
 434 #endif                          /* LJ_COMB */
 435
 436                                 // Ensure distance do not become so small that r^-12 overflows
 437                                 r2      = max(r2,NBNXN_MIN_RSQ);
 438
 439                                 inv_r   = rsqrt(r2);
 440                                 inv_r2  = inv_r * inv_r;
 441 #if !defined LJ_COMB_LB || defined CALC_ENERGIES
 442                                 inv_r6  = inv_r2 * inv_r2 * inv_r2;
 443 #if defined EXCLUSION_FORCES
 444                                 /* We could mask inv_r2, but with Ewald
 445                                  * masking both inv_r6 and F_invr is faster */
 446                                 inv_r6  *= int_bit;
 447 #endif                          /* EXCLUSION_FORCES */
 448
 449                                 F_invr  = inv_r6 * (c12 * inv_r6 - c6) * inv_r2;
 450 #if defined CALC_ENERGIES || defined LJ_POT_SWITCH
 451                                 E_lj_p  = int_bit * (c12 * (inv_r6 * inv_r6 + nbparam->repulsion_shift.cpot)*ONE_TWELVETH_F -
 452                                                      c6 * (inv_r6 + nbparam->dispersion_shift.cpot)*ONE_SIXTH_F);
 453
 454 #endif
 455 #else                           /* ! LJ_COMB_LB || CALC_ENERGIES */
 456                                 float sig_r  = sigma*inv_r;
 457                                 float sig_r2 = sig_r*sig_r;
 458                                 float sig_r6 = sig_r2*sig_r2*sig_r2;
 459 #if defined EXCLUSION_FORCES
 460                                 sig_r6 *= int_bit;
 461 #endif                          /* EXCLUSION_FORCES */
 462
 463                                 F_invr  = epsilon * sig_r6 * (sig_r6 - 1.0f) * inv_r2;
 464 #endif                          /* ! LJ_COMB_LB || CALC_ENERGIES */
 465
 466
 467 #ifdef LJ_FORCE_SWITCH
 468 #ifdef CALC_ENERGIES
 469                                 calculate_force_switch_F_E(nbparam, c6, c12, inv_r, r2, &F_invr, &E_lj_p);
 470 #else
 471                                 calculate_force_switch_F(nbparam, c6, c12, inv_r, r2, &F_invr);
 472 #endif /* CALC_ENERGIES */
 473 #endif /* LJ_FORCE_SWITCH */
 474
 475
 476 #ifdef LJ_EWALD
 477 #ifdef LJ_EWALD_COMB_GEOM
 478 #ifdef CALC_ENERGIES
 479                                 calculate_lj_ewald_comb_geom_F_E(nbfp_comb_climg2d, nbparam, typei, typej, r2, inv_r2, lje_coeff2, lje_coeff6_6, int_bit, &F_invr, &E_lj_p);
 480 #else
 481                                 calculate_lj_ewald_comb_geom_F(nbfp_comb_climg2d, typei, typej, r2, inv_r2, lje_coeff2, lje_coeff6_6, &F_invr);
 482 #endif                          /* CALC_ENERGIES */
 483 #elif defined LJ_EWALD_COMB_LB
 484                                 calculate_lj_ewald_comb_LB_F_E(nbfp_comb_climg2d, nbparam, typei, typej, r2, inv_r2, lje_coeff2, lje_coeff6_6,
 485 #ifdef CALC_ENERGIES
 486                                                                int_bit, true, &F_invr, &E_lj_p
 487 #else
 488                                                                0, false, &F_invr, 0
 489 #endif /* CALC_ENERGIES */
 490                                                                );
 491 #endif /* LJ_EWALD_COMB_GEOM */
 492 #endif /* LJ_EWALD */
 493
 494 #ifdef LJ_POT_SWITCH
 495 #ifdef CALC_ENERGIES
 496                                 calculate_potential_switch_F_E(nbparam, c6, c12, inv_r, r2, &F_invr, &E_lj_p);
 497 #else
 498                                 calculate_potential_switch_F(nbparam, c6, c12, inv_r, r2, &F_invr, &E_lj_p);
 499 #endif /* CALC_ENERGIES */
 500 #endif /* LJ_POT_SWITCH */
 501
 502 #ifdef VDW_CUTOFF_CHECK
 503                                 /* Separate VDW cut-off check to enable twin-range cut-offs
 504                                  * (rvdw < rcoulomb <= rlist)
 505                                  */
 506                                 vdw_in_range  = (r2 < rvdw_sq) ? 1.0f : 0.0f;
 507                                 F_invr       *= vdw_in_range;
 508 #ifdef CALC_ENERGIES
 509                                 E_lj_p       *= vdw_in_range;
 510 #endif
 511 #endif                          /* VDW_CUTOFF_CHECK */
 512
 513 #ifdef CALC_ENERGIES
 514                                 E_lj    += E_lj_p;
 515
 516 #endif
 517
 518
 519 #ifdef EL_CUTOFF
 520 #ifdef EXCLUSION_FORCES
 521                                 F_invr  += qi * qj_f * int_bit * inv_r2 * inv_r;
 522 #else
 523                                 F_invr  += qi * qj_f * inv_r2 * inv_r;
 524 #endif
 525 #endif
 526 #ifdef EL_RF
 527                                 F_invr  += qi * qj_f * (int_bit*inv_r2 * inv_r - two_k_rf);
 528 #endif
 529 #if defined EL_EWALD_ANA
 530                                 F_invr  += qi * qj_f * (int_bit*inv_r2*inv_r + pmecorrF(beta2*r2)*beta3);
 531 #elif defined EL_EWALD_TAB
 532                                 F_invr  += qi * qj_f * (int_bit*inv_r2 -
 533 #ifdef USE_TEXOBJ
 534                                                         interpolate_coulomb_force_r(nbparam->coulomb_tab_texobj, r2 * inv_r, coulomb_tab_scale)
 535 #else
 536                                                         interpolate_coulomb_force_r(coulomb_tab_climg2d, r2 * inv_r, coulomb_tab_scale)
 537 #endif /* USE_TEXOBJ */
 538                                                         ) * inv_r;
 539 #endif /* EL_EWALD_ANA/TAB */
 540
 541 #ifdef CALC_ENERGIES
 542 #ifdef EL_CUTOFF
 543                                 E_el    += qi * qj_f * (int_bit*inv_r - c_rf);
 544 #endif
 545 #ifdef EL_RF
 546                                 E_el    += qi * qj_f * (int_bit*inv_r + 0.5f * two_k_rf * r2 - c_rf);
 547 #endif
 548 #ifdef EL_EWALD_ANY
 549                                 /* 1.0f - erff is faster than erfcf */
 550                                 E_el    += qi * qj_f * (inv_r * (int_bit - erf(r2 * inv_r * beta)) - int_bit * ewald_shift);
 551 #endif                          /* EL_EWALD_ANY */
 552 #endif
 553                                 f_ij    = rv * F_invr;
 554
 555                                 /* accumulate j forces in registers */
 556                                 fcj_buf -= f_ij;
 557
 558                                 /* accumulate i forces in registers */
 559                                 fci_buf[ci_offset] += f_ij;
 560                             }
 561                         }
 562
 563                         /* shift the mask bit by 1 */
 564                         mask_ji += mask_ji;
 565                     }
 566
 567                     /* reduce j forces */
 568
 569                     /* store j forces in shmem */
 570                     f_buf[                  tidx] = fcj_buf.x;
 571                     f_buf[    FBUF_STRIDE + tidx] = fcj_buf.y;
 572                     f_buf[2 * FBUF_STRIDE + tidx] = fcj_buf.z;
 573
 574                     reduce_force_j_generic(f_buf, f, tidxi, tidxj, aj);
 575                 }
 576             }
 577 #ifdef PRUNE_NBL
 578             /* Update the imask with the new one which does not contain the
 579                out of range clusters anymore. */
 580
 581             pl_cj4[j4].imei[widx].imask = imask;
 582 #endif
 583         }
 584     }
 585
 586     /* skip central shifts when summing shift forces */
 587     if (nb_sci.shift == CENTRAL)
 588     {
 589         bCalcFshift = false;
 590     }
 591
 592     fshift_buf = 0.0f;
 593
 594     /* reduce i forces */
 595     for (ci_offset = 0; ci_offset < NCL_PER_SUPERCL; ci_offset++)
 596     {
 597         ai  = (sci * NCL_PER_SUPERCL + ci_offset) * CL_SIZE + tidxi;
 598
 599         f_buf[                  tidx] = fci_buf[ci_offset].x;
 600         f_buf[    FBUF_STRIDE + tidx] = fci_buf[ci_offset].y;
 601         f_buf[2 * FBUF_STRIDE + tidx] = fci_buf[ci_offset].z;
 602         barrier(CLK_LOCAL_MEM_FENCE);
 603         reduce_force_i(f_buf, f,
 604                        &fshift_buf, bCalcFshift,
 605                        tidxi, tidxj, ai);
 606         barrier(CLK_LOCAL_MEM_FENCE);
 607     }
 608
 609     /* add up local shift forces into global mem */
 610     if (bCalcFshift)
 611     {
 612         /* Only threads with tidxj < 3 will update fshift.
 613            The threads performing the update must be the same with the threads
 614            which stored the reduction result in reduce_force_i function
 615         */
 616         if (tidxj < 3)
 617             atomicAdd_g_f(&(fshift[3 * nb_sci.shift + tidxj]), fshift_buf);
 618     }
 619
 620 #ifdef CALC_ENERGIES
 621     /* flush the energies to shmem and reduce them */
 622     f_buf[              tidx] = E_lj;
 623     f_buf[FBUF_STRIDE + tidx] = E_el;
 624     reduce_energy_pow2(f_buf + (tidx & WARP_SIZE), e_lj, e_el, tidx & ~WARP_SIZE);
 625
 626 #endif
 627 }
 628
 629 #undef EL_EWALD_ANY
 630 #undef EXCLUSION_FORCES
 631 #undef LJ_EWALD
 632
 633 #undef LJ_COMB