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38 * \brief OpenCL non-bonded kernel.
40 * OpenCL 1.2 support is expected.
42 * \author Anca Hamuraru <anca@streamcomputing.eu>
43 * \author Szilárd Páll <pall.szilard@gmail.com>
44 * \ingroup module_nbnxm
47 /* Currently we enable CJ prefetch for AMD/NVIDIA and disable it for the "nowarp" kernel
48 * Note that this should precede the kernel_utils include.
50 #include "nbnxm_ocl_kernel_utils.clh"
52 /////////////////////////////////////////////////////////////////////////////////////////////////
54 #if defined EL_EWALD_ANA || defined EL_EWALD_TAB
55 /* Note: convenience macro, needs to be undef-ed at the end of the file. */
59 #if defined EL_EWALD_ANY || defined EL_RF || defined LJ_EWALD \
60 || (defined EL_CUTOFF && defined CALC_ENERGIES)
61 /* Macro to control the calculation of exclusion forces in the kernel
62 * We do that with Ewald (elec/vdw) and RF. Cut-off only has exclusion
65 * Note: convenience macro, needs to be undef-ed at the end of the file.
67 # define EXCLUSION_FORCES
70 #if defined LJ_EWALD_COMB_GEOM || defined LJ_EWALD_COMB_LB
71 /* Note: convenience macro, needs to be undef-ed at the end of the file. */
75 #if defined LJ_COMB_GEOM || defined LJ_COMB_LB
76 /* Note: convenience macro, needs to be undef-ed at the end of the file. */
81 Kernel launch parameters:
82 - #blocks = #pair lists, blockId = pair list Id
83 - #threads = CL_SIZE^2
84 - shmem = CL_SIZE^2 * sizeof(float)
86 Each thread calculates an i force-component taking one pair of i-j atoms.
88 TODO: implement 128 threads/wavefront by porting over the NTHREAD_Z/j4 loop
89 "horizontal splitting" over threads.
93 NB_KERNEL_FUNC_NAME differs from the CUDA equivalent as it is not a variadic macro due to OpenCL
94 not having a support for them, this version only takes exactly 2 arguments. Thus if more strings
95 need to be appended a new macro must be written or it must be directly appended here.
97 __attribute__((reqd_work_group_size(CL_SIZE, CL_SIZE, 1)))
98 #ifdef cl_intel_required_subgroup_size
99 __attribute__((intel_reqd_sub_group_size(SUBGROUP_SIZE)))
102 # ifdef CALC_ENERGIES
103 __kernel void NB_KERNEL_FUNC_NAME(nbnxn_kernel, _VF_prune_opencl)
105 __kernel void NB_KERNEL_FUNC_NAME(nbnxn_kernel, _F_prune_opencl)
108 # ifdef CALC_ENERGIES
109 __kernel void NB_KERNEL_FUNC_NAME(nbnxn_kernel, _VF_opencl)
111 __kernel void NB_KERNEL_FUNC_NAME(nbnxn_kernel, _F_opencl)
118 cl_nbparam_params_t nbparam_params, /* IN */
119 const __global float4* restrict xq, /* IN */
120 __global float* restrict f, /* OUT stores float3 values */
121 __global float* restrict gmx_unused e_lj, /* OUT */
122 __global float* restrict gmx_unused e_el, /* OUT */
123 __global float* restrict fshift, /* OUT stores float3 values */
125 const __global float2* restrict lj_comb, /* IN stores float2 values */
127 const __global int* restrict atom_types, /* IN */
129 const __global float* restrict shift_vec, /* IN stores float3 values */
130 __constant const float* gmx_unused nbfp_climg2d, /* IN */
131 __constant const float* gmx_unused nbfp_comb_climg2d, /* IN */
132 __constant const float* gmx_unused coulomb_tab_climg2d, /* IN */
133 const __global nbnxn_sci_t* pl_sci, /* IN */
137 __global nbnxn_cj4_t* pl_cj4, /* OUT / IN */
138 const __global nbnxn_excl_t* excl, /* IN */
139 int bCalcFshift, /* IN */
140 __local float4* xqib /* Pointer to dyn alloc'ed shmem */
143 /* convenience variables */
144 const cl_nbparam_params_t* const nbparam = &nbparam_params;
146 const float rcoulomb_sq = nbparam->rcoulomb_sq;
147 #ifdef VDW_CUTOFF_CHECK
148 const float rvdw_sq = nbparam_params.rvdw_sq;
151 const float two_k_rf = nbparam->two_k_rf;
154 const float coulomb_tab_scale = nbparam->coulomb_tab_scale;
157 const float beta2 = nbparam->ewald_beta * nbparam->ewald_beta;
158 const float beta3 = nbparam->ewald_beta * nbparam->ewald_beta * nbparam->ewald_beta;
161 const float rlist_sq = nbparam->rlistOuter_sq;
166 const float beta = nbparam->ewald_beta;
167 const float ewald_shift = nbparam->sh_ewald;
169 const float gmx_unused c_rf = nbparam->c_rf;
170 # endif /* EL_EWALD_ANY */
171 #endif /* CALC_ENERGIES */
173 /* thread/block/warp id-s */
174 const int tidxi = get_local_id(0);
175 const int tidxj = get_local_id(1);
176 const int tidx = (int)(get_local_id(1) * get_local_size(0) + get_local_id(0));
177 const int bidx = get_group_id(0);
178 const int widx = tidx / WARP_SIZE; /* warp index */
180 /*! i-cluster interaction mask for a super-cluster with all c_nbnxnGpuNumClusterPerSupercluster=8 bits set */
181 const unsigned superClInteractionMask = ((1U << c_nbnxnGpuNumClusterPerSupercluster) - 1U);
183 #define LOCAL_OFFSET (xqib + c_nbnxnGpuNumClusterPerSupercluster * CL_SIZE)
186 /* shmem buffer for cj, for both warps separately */
187 cjs = (__local int*)(LOCAL_OFFSET);
189 # define LOCAL_OFFSET (cjs + 2 * c_nbnxnGpuJgroupSize)
190 #endif // USE_CJ_PREFETCH
194 /* shmem buffer for i atom-type pre-loading */
195 __local int* atib = (__local int*)(LOCAL_OFFSET); //NOLINT(google-readability-casting)
197 # define LOCAL_OFFSET (atib + c_nbnxnGpuNumClusterPerSupercluster * CL_SIZE)
199 __local float2* ljcpib = (__local float2*)(LOCAL_OFFSET);
201 # define LOCAL_OFFSET (ljcpib + c_nbnxnGpuNumClusterPerSupercluster * CL_SIZE)
206 /* shmem j force buffer */
207 __local float* f_buf = (__local float*)(LOCAL_OFFSET);
209 # define LOCAL_OFFSET (f_buf + CL_SIZE * CL_SIZE * 3)
211 __local float* f_buf = 0;
213 #if !USE_SUBGROUP_ANY
214 /* Local buffer used to implement __any warp vote function from CUDA.
215 volatile is used to avoid compiler optimizations for AMD builds. */
216 //NOLINTNEXTLINE(google-readability-casting)
217 volatile __local int* warp_any = (__local int*)(LOCAL_OFFSET);
219 __local int gmx_unused* warp_any = 0;
223 const nbnxn_sci_t nb_sci = pl_sci[bidx]; /* my i super-cluster's index = current bidx */
224 const int sci = nb_sci.sci; /* super-cluster */
225 const int cij4_start = nb_sci.cj4_ind_start; /* first ...*/
226 const int cij4_end = nb_sci.cj4_ind_end; /* and last index of j clusters */
228 for (int i = 0; i < c_nbnxnGpuNumClusterPerSupercluster; i += CL_SIZE)
230 /* Pre-load i-atom x and q into shared memory */
231 const int ci = sci * c_nbnxnGpuNumClusterPerSupercluster + tidxj + i;
232 const int ai = ci * CL_SIZE + tidxi;
234 float4 xqbuf = xq[ai]
235 + (float4)(shift_vec[3 * nb_sci.shift], shift_vec[3 * nb_sci.shift + 1],
236 shift_vec[3 * nb_sci.shift + 2], 0.0F);
237 xqbuf.w *= nbparam->epsfac;
238 xqib[(tidxj + i) * CL_SIZE + tidxi] = xqbuf;
241 /* Pre-load the i-atom types into shared memory */
242 atib[(tidxj + i) * CL_SIZE + tidxi] = atom_types[ai];
244 ljcpib[(tidxj + i) * CL_SIZE + tidxi] = lj_comb[ai];
248 #if !USE_SUBGROUP_ANY
249 /* Initialise warp vote. (8x8 block) 2 warps for nvidia */
250 if (tidx == 0 || tidx == WARP_SIZE)
255 barrier(CLK_LOCAL_MEM_FENCE);
257 float3 fci_buf[c_nbnxnGpuNumClusterPerSupercluster]; /* i force buffer */
258 for (int ci_offset = 0; ci_offset < c_nbnxnGpuNumClusterPerSupercluster; ci_offset++)
260 fci_buf[ci_offset] = (float3)(0.0F);
264 /* TODO: we are trading registers with flops by keeping lje_coeff-s, try re-calculating it later */
265 const float lje_coeff2 = nbparam->ewaldcoeff_lj * nbparam->ewaldcoeff_lj;
266 const float lje_coeff6_6 = lje_coeff2 * lje_coeff2 * lje_coeff2 * ONE_SIXTH_F;
267 #endif /* LJ_EWALD */
274 # if defined EXCLUSION_FORCES /* Ewald or RF */
275 if (nb_sci.shift == CENTRAL && pl_cj4[cij4_start].cj[0] == sci * c_nbnxnGpuNumClusterPerSupercluster)
277 /* we have the diagonal: add the charge and LJ self interaction energy term */
278 for (int i = 0; i < c_nbnxnGpuNumClusterPerSupercluster; i++)
280 # if defined EL_EWALD_ANY || defined EL_RF || defined EL_CUTOFF
281 const float qi = xqib[i * CL_SIZE + tidxi].w;
284 # if defined LJ_EWALD
285 E_lj += nbfp_climg2d[atom_types[(sci * c_nbnxnGpuNumClusterPerSupercluster + i) * CL_SIZE + tidxi]
287 # endif /* LJ_EWALD */
290 /* divide the self term(s) equally over the j-threads, then multiply with the coefficients. */
293 E_lj *= HALF_F * ONE_SIXTH_F * lje_coeff6_6;
294 # endif /* LJ_EWALD */
296 # if defined EL_EWALD_ANY || defined EL_RF || defined EL_CUTOFF
297 /* Correct for epsfac^2 due to adding qi^2 */
298 E_el /= nbparam->epsfac * CL_SIZE;
299 # if defined EL_RF || defined EL_CUTOFF
300 E_el *= -HALF_F * c_rf;
302 E_el *= -beta * M_FLOAT_1_SQRTPI; /* last factor 1/sqrt(pi) */
304 # endif /* EL_EWALD_ANY || defined EL_RF || defined EL_CUTOFF */
306 # endif /* EXCLUSION_FORCES */
308 #endif /* CALC_ENERGIES */
310 #ifdef EXCLUSION_FORCES
311 const int nonSelfInteraction = !(nb_sci.shift == CENTRAL & tidxj <= tidxi);
314 /* loop over the j clusters = seen by any of the atoms in the current super-cluster */
315 for (int j4 = cij4_start; j4 < cij4_end; j4++)
317 const int wexcl_idx = pl_cj4[j4].imei[widx].excl_ind;
318 unsigned int imask = pl_cj4[j4].imei[widx].imask;
319 const unsigned int wexcl = excl[wexcl_idx].pair[(tidx) & (WARP_SIZE - 1)];
321 preloadCj4(&cjs, pl_cj4[j4].cj, tidxi, tidxj, imask != 0U);
327 /* Unrolling this loop improves performance without pruning but
328 * with pruning it leads to slowdown.
330 * Tested with driver 1800.5
332 * TODO: check loop unrolling with NVIDIA OpenCL
334 #if !defined PRUNE_NBL && !defined _NVIDIA_SOURCE_
337 for (int jm = 0; jm < c_nbnxnGpuJgroupSize; jm++)
339 if (imask & (superClInteractionMask << (jm * c_nbnxnGpuNumClusterPerSupercluster)))
341 unsigned int mask_ji = (1U << (jm * c_nbnxnGpuNumClusterPerSupercluster));
343 const int cj = loadCj(cjs, pl_cj4[j4].cj, jm, tidxi, tidxj);
344 const int aj = cj * CL_SIZE + tidxj;
346 /* load j atom data */
347 const float4 xjqbuf = xq[aj];
348 const float3 xj = (float3)(xjqbuf.xyz);
349 const float qj_f = xjqbuf.w;
351 const int typej = atom_types[aj];
353 const float2 ljcp_j = lj_comb[aj];
356 float3 fcj_buf = (float3)(0.0F);
358 #if !defined PRUNE_NBL
361 for (int i = 0; i < c_nbnxnGpuNumClusterPerSupercluster; i++)
365 const int gmx_unused ci = sci * c_nbnxnGpuNumClusterPerSupercluster + i; /* i cluster index */
367 /* all threads load an atom from i cluster ci into shmem! */
368 const float4 xiqbuf = xqib[i * CL_SIZE + tidxi];
369 const float3 xi = (float3)(xiqbuf.xyz);
371 /* distance between i and j atoms */
372 const float3 rv = xi - xj;
373 float r2 = norm2(rv);
376 if (!gmx_sub_group_any(warp_any, widx, r2 < rlist_sq))
382 const float int_bit = (wexcl & mask_ji) ? 1.0F : 0.0F;
384 /* cutoff & exclusion check */
385 #ifdef EXCLUSION_FORCES
386 if ((r2 < rcoulomb_sq) * (nonSelfInteraction | (ci != cj)))
388 if ((float)(r2 < rcoulomb_sq) * int_bit != 0.0F)
391 /* load the rest of the i-atom parameters */
392 const float qi = xiqbuf.w;
395 const int typei = atib[i * CL_SIZE + tidxi];
397 const float2 ljcp_i = ljcpib[i * CL_SIZE + tidxi];
399 #else /* IATYPE_SHMEM */
400 const int ai = ci * CL_SIZE + tidxi; /* i atom index */
403 const int typei = atom_types[ai];
405 const float2 ljcp_i = lj_comb[ai];
407 #endif /* IATYPE_SHMEM */
408 /* LJ 6*C6 and 12*C12 */
410 const float c6 = nbfp_climg2d[2 * (ntypes * typei + typej)];
411 const float c12 = nbfp_climg2d[2 * (ntypes * typei + typej) + 1];
414 const float c6 = ljcp_i.x * ljcp_j.x;
415 const float c12 = ljcp_i.y * ljcp_j.y;
417 /* LJ 2^(1/6)*sigma and 12*epsilon */
418 const float sigma = ljcp_i.x + ljcp_j.x;
419 const float epsilon = ljcp_i.y * ljcp_j.y;
420 # if defined CALC_ENERGIES || defined LJ_FORCE_SWITCH || defined LJ_POT_SWITCH
422 convert_sigma_epsilon_to_c6_c12(sigma, epsilon, &c6, &c12);
424 # endif /* LJ_COMB_GEOM */
427 // Ensure distance do not become so small that r^-12 overflows.
428 // Cast to float to ensure the correct built-in max() function
430 r2 = max(r2, (float)c_nbnxnMinDistanceSquared);
432 const float inv_r = rsqrt(r2);
433 const float inv_r2 = inv_r * inv_r;
434 #if !defined LJ_COMB_LB || defined CALC_ENERGIES
435 float inv_r6 = inv_r2 * inv_r2 * inv_r2;
436 # if defined EXCLUSION_FORCES
437 /* We could mask inv_r2, but with Ewald
438 * masking both inv_r6 and F_invr is faster */
440 # endif /* EXCLUSION_FORCES */
442 float F_invr = inv_r6 * (c12 * inv_r6 - c6) * inv_r2;
443 # if defined CALC_ENERGIES || defined LJ_POT_SWITCH
446 * (c12 * (inv_r6 * inv_r6 + nbparam->repulsion_shift.cpot) * ONE_TWELVETH_F
447 - c6 * (inv_r6 + nbparam->dispersion_shift.cpot) * ONE_SIXTH_F);
450 #else /* ! LJ_COMB_LB || CALC_ENERGIES */
451 const float sig_r = sigma * inv_r;
452 const float sig_r2 = sig_r * sig_r;
453 float sig_r6 = sig_r2 * sig_r2 * sig_r2;
454 # if defined EXCLUSION_FORCES
456 # endif /* EXCLUSION_FORCES */
458 float F_invr = epsilon * sig_r6 * (sig_r6 - 1.0F) * inv_r2;
459 #endif /* ! LJ_COMB_LB || CALC_ENERGIES */
462 #ifdef LJ_FORCE_SWITCH
463 # ifdef CALC_ENERGIES
464 calculate_force_switch_F_E(nbparam, c6, c12, inv_r, r2, &F_invr, &E_lj_p);
466 calculate_force_switch_F(nbparam, c6, c12, inv_r, r2, &F_invr);
467 # endif /* CALC_ENERGIES */
468 #endif /* LJ_FORCE_SWITCH */
472 # ifdef LJ_EWALD_COMB_GEOM
473 # ifdef CALC_ENERGIES
474 calculate_lj_ewald_comb_geom_F_E(
475 nbfp_comb_climg2d, nbparam, typei, typej, r2, inv_r2,
476 lje_coeff2, lje_coeff6_6, int_bit, &F_invr, &E_lj_p);
478 calculate_lj_ewald_comb_geom_F(nbfp_comb_climg2d, typei, typej, r2, inv_r2,
479 lje_coeff2, lje_coeff6_6, &F_invr);
480 # endif /* CALC_ENERGIES */
481 # elif defined LJ_EWALD_COMB_LB
482 calculate_lj_ewald_comb_LB_F_E(nbfp_comb_climg2d, nbparam, typei, typej,
483 r2, inv_r2, lje_coeff2, lje_coeff6_6,
484 # ifdef CALC_ENERGIES
485 int_bit, true, &F_invr, &E_lj_p
488 # endif /* CALC_ENERGIES */
490 # endif /* LJ_EWALD_COMB_GEOM */
491 #endif /* LJ_EWALD */
494 # ifdef CALC_ENERGIES
495 calculate_potential_switch_F_E(nbparam, inv_r, r2, &F_invr, &E_lj_p);
497 calculate_potential_switch_F(nbparam, inv_r, r2, &F_invr, &E_lj_p);
498 # endif /* CALC_ENERGIES */
499 #endif /* LJ_POT_SWITCH */
501 #ifdef VDW_CUTOFF_CHECK
502 /* Separate VDW cut-off check to enable twin-range cut-offs
503 * (rvdw < rcoulomb <= rlist)
505 const float vdw_in_range = (r2 < rvdw_sq) ? 1.0F : 0.0F;
506 F_invr *= vdw_in_range;
507 # ifdef CALC_ENERGIES
508 E_lj_p *= vdw_in_range;
510 #endif /* VDW_CUTOFF_CHECK */
519 # ifdef EXCLUSION_FORCES
520 F_invr += qi * qj_f * int_bit * inv_r2 * inv_r;
522 F_invr += qi * qj_f * inv_r2 * inv_r;
526 F_invr += qi * qj_f * (int_bit * inv_r2 * inv_r - two_k_rf);
528 #if defined EL_EWALD_ANA
530 * (int_bit * inv_r2 * inv_r + pmecorrF(beta2 * r2) * beta3);
531 #elif defined EL_EWALD_TAB
534 - interpolate_coulomb_force_r(coulomb_tab_climg2d, r2 * inv_r,
537 #endif /* EL_EWALD_ANA/TAB */
541 E_el += qi * qj_f * (int_bit * inv_r - c_rf);
544 E_el += qi * qj_f * (int_bit * inv_r + HALF_F * two_k_rf * r2 - c_rf);
547 /* 1.0F - erff is faster than erfcf */
549 * (inv_r * (int_bit - erf(r2 * inv_r * beta)) - int_bit * ewald_shift);
550 # endif /* EL_EWALD_ANY */
552 const float3 f_ij = rv * F_invr;
554 /* accumulate j forces in registers */
557 /* accumulate i forces in registers */
562 /* shift the mask bit by 1 */
566 /* reduce j forces */
567 reduce_force_j(f_buf, fcj_buf, f, tidxi, tidxj, aj);
571 /* Update the imask with the new one which does not contain the
572 out of range clusters anymore. */
574 pl_cj4[j4].imei[widx].imask = imask;
579 /* skip central shifts when summing shift forces */
580 if (nb_sci.shift == CENTRAL)
584 /* reduce i forces */
585 reduce_force_i_and_shift(f_buf, fci_buf, f, bCalcFshift != 0, tidxi, tidxj, sci, nb_sci.shift, fshift);
588 reduce_energy(f_buf, E_lj, E_el, e_lj, e_el, tidx);
593 #undef EXCLUSION_FORCES
598 #undef USE_CJ_PREFETCH