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36 * \brief Common functions for the different NBNXN GPU implementations.
38 * \author Berk Hess <hess@kth.se>
40 * \ingroup module_nbnxm
45 #include "gromacs/domdec/domdec.h"
46 #include "gromacs/domdec/domdec_struct.h"
47 #include "gromacs/hardware/hw_info.h"
48 #include "gromacs/mdlib/gmx_omp_nthreads.h"
49 #include "gromacs/mdtypes/commrec.h"
50 #include "gromacs/mdtypes/forcerec.h"
51 #include "gromacs/mdtypes/inputrec.h"
52 #include "gromacs/nbnxm/gpu_data_mgmt.h"
53 #include "gromacs/nbnxm/nbnxm.h"
54 #include "gromacs/nbnxm/pairlist_tuning.h"
55 #include "gromacs/simd/simd.h"
56 #include "gromacs/utility/fatalerror.h"
57 #include "gromacs/utility/logger.h"
60 #include "gpu_types.h"
62 #include "nbnxm_geometry.h"
63 #include "nbnxm_simd.h"
65 #include "pairlistset.h"
66 #include "pairlistsets.h"
67 #include "pairsearch.h"
72 /*! \brief Resources that can be used to execute non-bonded kernels on */
73 enum class NonbondedResource : int
80 /*! \brief Returns whether CPU SIMD support exists for the given inputrec
82 * If the return value is FALSE and fplog/cr != NULL, prints a fallback
83 * message to fplog/stderr.
85 static gmx_bool nbnxn_simd_supported(const gmx::MDLogger& mdlog, const t_inputrec* ir)
87 if (ir->vdwtype == evdwPME && ir->ljpme_combination_rule == eljpmeLB)
89 /* LJ PME with LB combination rule does 7 mesh operations.
90 * This so slow that we don't compile SIMD non-bonded kernels
92 GMX_LOG(mdlog.warning)
95 "LJ-PME with Lorentz-Berthelot is not supported with SIMD kernels, falling "
96 "back to plain C kernels");
103 /*! \brief Returns the most suitable CPU kernel type and Ewald handling */
104 static KernelSetup pick_nbnxn_kernel_cpu(const t_inputrec gmx_unused* ir,
105 const gmx_hw_info_t gmx_unused& hardwareInfo)
107 KernelSetup kernelSetup;
111 kernelSetup.kernelType = KernelType::Cpu4x4_PlainC;
112 kernelSetup.ewaldExclusionType = EwaldExclusionType::Table;
116 #ifdef GMX_NBNXN_SIMD_4XN
117 kernelSetup.kernelType = KernelType::Cpu4xN_Simd_4xN;
119 #ifdef GMX_NBNXN_SIMD_2XNN
120 kernelSetup.kernelType = KernelType::Cpu4xN_Simd_2xNN;
123 #if defined GMX_NBNXN_SIMD_2XNN && defined GMX_NBNXN_SIMD_4XN
124 /* We need to choose if we want 2x(N+N) or 4xN kernels.
125 * This is based on the SIMD acceleration choice and CPU information
126 * detected at runtime.
128 * 4xN calculates more (zero) interactions, but has less pair-search
129 * work and much better kernel instruction scheduling.
131 * Up till now we have only seen that on Intel Sandy/Ivy Bridge,
132 * which doesn't have FMA, both the analytical and tabulated Ewald
133 * kernels have similar pair rates for 4x8 and 2x(4+4), so we choose
134 * 2x(4+4) because it results in significantly fewer pairs.
135 * For RF, the raw pair rate of the 4x8 kernel is higher than 2x(4+4),
136 * 10% with HT, 50% without HT. As we currently don't detect the actual
137 * use of HT, use 4x8 to avoid a potential performance hit.
138 * On Intel Haswell 4x8 is always faster.
140 kernelSetup.kernelType = KernelType::Cpu4xN_Simd_4xN;
142 if (!GMX_SIMD_HAVE_FMA && (EEL_PME_EWALD(ir->coulombtype) || EVDW_PME(ir->vdwtype)))
144 /* We have Ewald kernels without FMA (Intel Sandy/Ivy Bridge).
145 * There are enough instructions to make 2x(4+4) efficient.
147 kernelSetup.kernelType = KernelType::Cpu4xN_Simd_2xNN;
150 if (hardwareInfo.haveAmdZen1Cpu)
152 /* One 256-bit FMA per cycle makes 2xNN faster */
153 kernelSetup.kernelType = KernelType::Cpu4xN_Simd_2xNN;
155 #endif /* GMX_NBNXN_SIMD_2XNN && GMX_NBNXN_SIMD_4XN */
158 if (getenv("GMX_NBNXN_SIMD_4XN") != nullptr)
160 #ifdef GMX_NBNXN_SIMD_4XN
161 kernelSetup.kernelType = KernelType::Cpu4xN_Simd_4xN;
164 "SIMD 4xN kernels requested, but GROMACS has been compiled without support "
165 "for these kernels");
168 if (getenv("GMX_NBNXN_SIMD_2XNN") != nullptr)
170 #ifdef GMX_NBNXN_SIMD_2XNN
171 kernelSetup.kernelType = KernelType::Cpu4xN_Simd_2xNN;
174 "SIMD 2x(N+N) kernels requested, but GROMACS has been compiled without "
175 "support for these kernels");
179 /* Analytical Ewald exclusion correction is only an option in
181 * Since table lookup's don't parallelize with SIMD, analytical
182 * will probably always be faster for a SIMD width of 8 or more.
183 * With FMA analytical is sometimes faster for a width if 4 as well.
184 * In single precision, this is faster on Bulldozer.
185 * On AMD Zen, tabulated Ewald kernels are faster on all 4 combinations
186 * of single or double precision and 128 or 256-bit AVX2.
190 (GMX_SIMD_REAL_WIDTH >= 8 || (GMX_SIMD_REAL_WIDTH >= 4 && GMX_SIMD_HAVE_FMA && !GMX_DOUBLE)) &&
192 !hardwareInfo.haveAmdZen1Cpu)
194 kernelSetup.ewaldExclusionType = EwaldExclusionType::Analytical;
198 kernelSetup.ewaldExclusionType = EwaldExclusionType::Table;
200 if (getenv("GMX_NBNXN_EWALD_TABLE") != nullptr)
202 kernelSetup.ewaldExclusionType = EwaldExclusionType::Table;
204 if (getenv("GMX_NBNXN_EWALD_ANALYTICAL") != nullptr)
206 kernelSetup.ewaldExclusionType = EwaldExclusionType::Analytical;
213 const char* lookup_kernel_name(const KernelType kernelType)
215 const char* returnvalue = nullptr;
218 case KernelType::NotSet: returnvalue = "not set"; break;
219 case KernelType::Cpu4x4_PlainC: returnvalue = "plain C"; break;
220 case KernelType::Cpu4xN_Simd_4xN:
221 case KernelType::Cpu4xN_Simd_2xNN:
223 returnvalue = "SIMD";
225 returnvalue = "not available";
228 case KernelType::Gpu8x8x8: returnvalue = "GPU"; break;
229 case KernelType::Cpu8x8x8_PlainC: returnvalue = "plain C"; break;
231 default: gmx_fatal(FARGS, "Illegal kernel type selected");
236 /*! \brief Returns the most suitable kernel type and Ewald handling */
237 static KernelSetup pick_nbnxn_kernel(const gmx::MDLogger& mdlog,
238 gmx_bool use_simd_kernels,
239 const gmx_hw_info_t& hardwareInfo,
240 const NonbondedResource& nonbondedResource,
241 const t_inputrec* ir,
242 gmx_bool bDoNonbonded)
244 KernelSetup kernelSetup;
246 if (nonbondedResource == NonbondedResource::EmulateGpu)
248 kernelSetup.kernelType = KernelType::Cpu8x8x8_PlainC;
249 kernelSetup.ewaldExclusionType = EwaldExclusionType::DecidedByGpuModule;
253 GMX_LOG(mdlog.warning)
255 .appendText("Emulating a GPU run on the CPU (slow)");
258 else if (nonbondedResource == NonbondedResource::Gpu)
260 kernelSetup.kernelType = KernelType::Gpu8x8x8;
261 kernelSetup.ewaldExclusionType = EwaldExclusionType::DecidedByGpuModule;
265 if (use_simd_kernels && nbnxn_simd_supported(mdlog, ir))
267 kernelSetup = pick_nbnxn_kernel_cpu(ir, hardwareInfo);
271 kernelSetup.kernelType = KernelType::Cpu4x4_PlainC;
272 kernelSetup.ewaldExclusionType = EwaldExclusionType::Analytical;
280 .appendTextFormatted("Using %s %dx%d nonbonded short-range kernels",
281 lookup_kernel_name(kernelSetup.kernelType),
282 IClusterSizePerKernelType[kernelSetup.kernelType],
283 JClusterSizePerKernelType[kernelSetup.kernelType]);
285 if (KernelType::Cpu4x4_PlainC == kernelSetup.kernelType
286 || KernelType::Cpu8x8x8_PlainC == kernelSetup.kernelType)
288 GMX_LOG(mdlog.warning)
290 .appendTextFormatted(
291 "WARNING: Using the slow %s kernels. This should\n"
292 "not happen during routine usage on supported platforms.",
293 lookup_kernel_name(kernelSetup.kernelType));
297 GMX_RELEASE_ASSERT(kernelSetup.kernelType != KernelType::NotSet
298 && kernelSetup.ewaldExclusionType != EwaldExclusionType::NotSet,
299 "All kernel setup parameters should be set here");
306 PairlistSets::PairlistSets(const PairlistParams& pairlistParams,
307 const bool haveMultipleDomains,
308 const int minimumIlistCountForGpuBalancing) :
309 params_(pairlistParams),
310 minimumIlistCountForGpuBalancing_(minimumIlistCountForGpuBalancing)
312 localSet_ = std::make_unique<PairlistSet>(gmx::InteractionLocality::Local, params_);
314 if (haveMultipleDomains)
316 nonlocalSet_ = std::make_unique<PairlistSet>(gmx::InteractionLocality::NonLocal, params_);
323 /*! \brief Gets and returns the minimum i-list count for balacing based on the GPU used or env.var. when set */
324 static int getMinimumIlistCountForGpuBalancing(gmx_nbnxn_gpu_t* nbnxmGpu)
326 int minimumIlistCount;
328 if (const char* env = getenv("GMX_NB_MIN_CI"))
332 minimumIlistCount = strtol(env, &end, 10);
333 if (!end || (*end != 0) || minimumIlistCount < 0)
336 "Invalid value passed in GMX_NB_MIN_CI=%s, non-negative integer required", env);
341 fprintf(debug, "Neighbor-list balancing parameter: %d (passed as env. var.)\n",
347 minimumIlistCount = gpu_min_ci_balanced(nbnxmGpu);
351 "Neighbor-list balancing parameter: %d (auto-adjusted to the number of GPU "
352 "multi-processors)\n",
357 return minimumIlistCount;
360 std::unique_ptr<nonbonded_verlet_t> init_nb_verlet(const gmx::MDLogger& mdlog,
361 gmx_bool bFEP_NonBonded,
362 const t_inputrec* ir,
363 const t_forcerec* fr,
365 const gmx_hw_info_t& hardwareInfo,
366 const gmx_device_info_t* deviceInfo,
367 const gmx_mtop_t* mtop,
369 gmx_wallcycle* wcycle)
371 const bool emulateGpu = (getenv("GMX_EMULATE_GPU") != nullptr);
372 const bool useGpu = deviceInfo != nullptr;
374 GMX_RELEASE_ASSERT(!(emulateGpu && useGpu),
375 "When GPU emulation is active, there cannot be a GPU assignment");
377 NonbondedResource nonbondedResource;
380 nonbondedResource = NonbondedResource::Gpu;
384 nonbondedResource = NonbondedResource::EmulateGpu;
388 nonbondedResource = NonbondedResource::Cpu;
391 Nbnxm::KernelSetup kernelSetup = pick_nbnxn_kernel(mdlog, fr->use_simd_kernels, hardwareInfo,
392 nonbondedResource, ir, fr->bNonbonded);
394 const bool haveMultipleDomains = (DOMAINDECOMP(cr) && cr->dd->nnodes > 1);
396 PairlistParams pairlistParams(kernelSetup.kernelType, bFEP_NonBonded, ir->rlist,
397 havePPDomainDecomposition(cr));
399 setupDynamicPairlistPruning(mdlog, ir, mtop, box, fr->ic, &pairlistParams);
401 int enbnxninitcombrule;
402 if (fr->ic->vdwtype == evdwCUT
403 && (fr->ic->vdw_modifier == eintmodNONE || fr->ic->vdw_modifier == eintmodPOTSHIFT)
404 && getenv("GMX_NO_LJ_COMB_RULE") == nullptr)
406 /* Plain LJ cut-off: we can optimize with combination rules */
407 enbnxninitcombrule = enbnxninitcombruleDETECT;
409 else if (fr->ic->vdwtype == evdwPME)
411 /* LJ-PME: we need to use a combination rule for the grid */
412 if (fr->ljpme_combination_rule == eljpmeGEOM)
414 enbnxninitcombrule = enbnxninitcombruleGEOM;
418 enbnxninitcombrule = enbnxninitcombruleLB;
423 /* We use a full combination matrix: no rule required */
424 enbnxninitcombrule = enbnxninitcombruleNONE;
427 auto pinPolicy = (useGpu ? gmx::PinningPolicy::PinnedIfSupported : gmx::PinningPolicy::CannotBePinned);
429 auto nbat = std::make_unique<nbnxn_atomdata_t>(pinPolicy);
431 int mimimumNumEnergyGroupNonbonded = ir->opts.ngener;
432 if (ir->opts.ngener - ir->nwall == 1)
434 /* We have only one non-wall energy group, we do not need energy group
435 * support in the non-bondeds kernels, since all non-bonded energy
436 * contributions go to the first element of the energy group matrix.
438 mimimumNumEnergyGroupNonbonded = 1;
440 nbnxn_atomdata_init(mdlog, nbat.get(), kernelSetup.kernelType, enbnxninitcombrule, fr->ntype,
441 fr->nbfp, mimimumNumEnergyGroupNonbonded,
442 (useGpu || emulateGpu) ? 1 : gmx_omp_nthreads_get(emntNonbonded));
444 gmx_nbnxn_gpu_t* gpu_nbv = nullptr;
445 int minimumIlistCountForGpuBalancing = 0;
448 /* init the NxN GPU data; the last argument tells whether we'll have
449 * both local and non-local NB calculation on GPU */
450 gpu_nbv = gpu_init(deviceInfo, fr->ic, pairlistParams, nbat.get(), cr->nodeid, haveMultipleDomains);
452 minimumIlistCountForGpuBalancing = getMinimumIlistCountForGpuBalancing(gpu_nbv);
455 auto pairlistSets = std::make_unique<PairlistSets>(pairlistParams, haveMultipleDomains,
456 minimumIlistCountForGpuBalancing);
458 auto pairSearch = std::make_unique<PairSearch>(
459 ir->ePBC, EI_TPI(ir->eI), DOMAINDECOMP(cr) ? &cr->dd->numCells : nullptr,
460 DOMAINDECOMP(cr) ? domdec_zones(cr->dd) : nullptr, pairlistParams.pairlistType,
461 bFEP_NonBonded, gmx_omp_nthreads_get(emntPairsearch), pinPolicy);
463 return std::make_unique<nonbonded_verlet_t>(std::move(pairlistSets), std::move(pairSearch),
464 std::move(nbat), kernelSetup, gpu_nbv, wcycle);
469 nonbonded_verlet_t::nonbonded_verlet_t(std::unique_ptr<PairlistSets> pairlistSets,
470 std::unique_ptr<PairSearch> pairSearch,
471 std::unique_ptr<nbnxn_atomdata_t> nbat_in,
472 const Nbnxm::KernelSetup& kernelSetup,
473 gmx_nbnxn_gpu_t* gpu_nbv_ptr,
474 gmx_wallcycle* wcycle) :
475 pairlistSets_(std::move(pairlistSets)),
476 pairSearch_(std::move(pairSearch)),
477 nbat(std::move(nbat_in)),
478 kernelSetup_(kernelSetup),
482 GMX_RELEASE_ASSERT(pairlistSets_, "Need valid pairlistSets");
483 GMX_RELEASE_ASSERT(pairSearch_, "Need valid search object");
484 GMX_RELEASE_ASSERT(nbat, "Need valid atomdata object");
487 nonbonded_verlet_t::~nonbonded_verlet_t()
489 Nbnxm::gpu_free(gpu_nbv);