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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/mdtypes/interaction_const.h"
53 #include "gromacs/nbnxm/atomdata.h"
54 #include "gromacs/nbnxm/gpu_data_mgmt.h"
55 #include "gromacs/nbnxm/nbnxm.h"
56 #include "gromacs/nbnxm/pairlist_tuning.h"
57 #include "gromacs/simd/simd.h"
58 #include "gromacs/topology/mtop_util.h"
59 #include "gromacs/utility/fatalerror.h"
60 #include "gromacs/utility/logger.h"
63 #include "nbnxm_geometry.h"
64 #include "nbnxm_simd.h"
66 #include "pairlistset.h"
67 #include "pairlistsets.h"
68 #include "pairsearch.h"
73 /*! \brief Resources that can be used to execute non-bonded kernels on */
74 enum class NonbondedResource : int
81 /*! \brief Returns whether CPU SIMD support exists for the given inputrec
83 * If the return value is FALSE and fplog/cr != NULL, prints a fallback
84 * message to fplog/stderr.
86 static gmx_bool nbnxn_simd_supported(const gmx::MDLogger& mdlog, const t_inputrec* ir)
88 if (ir->vdwtype == evdwPME && ir->ljpme_combination_rule == eljpmeLB)
90 /* LJ PME with LB combination rule does 7 mesh operations.
91 * This so slow that we don't compile SIMD non-bonded kernels
93 GMX_LOG(mdlog.warning)
96 "LJ-PME with Lorentz-Berthelot is not supported with SIMD kernels, falling "
97 "back to plain C kernels");
104 /*! \brief Returns the most suitable CPU kernel type and Ewald handling */
105 static KernelSetup pick_nbnxn_kernel_cpu(const t_inputrec gmx_unused* ir,
106 const gmx_hw_info_t gmx_unused& hardwareInfo)
108 KernelSetup kernelSetup;
112 kernelSetup.kernelType = KernelType::Cpu4x4_PlainC;
113 kernelSetup.ewaldExclusionType = EwaldExclusionType::Table;
117 #ifdef GMX_NBNXN_SIMD_4XN
118 kernelSetup.kernelType = KernelType::Cpu4xN_Simd_4xN;
120 #ifdef GMX_NBNXN_SIMD_2XNN
121 kernelSetup.kernelType = KernelType::Cpu4xN_Simd_2xNN;
124 #if defined GMX_NBNXN_SIMD_2XNN && defined GMX_NBNXN_SIMD_4XN
125 /* We need to choose if we want 2x(N+N) or 4xN kernels.
126 * This is based on the SIMD acceleration choice and CPU information
127 * detected at runtime.
129 * 4xN calculates more (zero) interactions, but has less pair-search
130 * work and much better kernel instruction scheduling.
132 * Up till now we have only seen that on Intel Sandy/Ivy Bridge,
133 * which doesn't have FMA, both the analytical and tabulated Ewald
134 * kernels have similar pair rates for 4x8 and 2x(4+4), so we choose
135 * 2x(4+4) because it results in significantly fewer pairs.
136 * For RF, the raw pair rate of the 4x8 kernel is higher than 2x(4+4),
137 * 10% with HT, 50% without HT. As we currently don't detect the actual
138 * use of HT, use 4x8 to avoid a potential performance hit.
139 * On Intel Haswell 4x8 is always faster.
141 kernelSetup.kernelType = KernelType::Cpu4xN_Simd_4xN;
143 if (!GMX_SIMD_HAVE_FMA && (EEL_PME_EWALD(ir->coulombtype) || EVDW_PME(ir->vdwtype)))
145 /* We have Ewald kernels without FMA (Intel Sandy/Ivy Bridge).
146 * There are enough instructions to make 2x(4+4) efficient.
148 kernelSetup.kernelType = KernelType::Cpu4xN_Simd_2xNN;
151 if (hardwareInfo.haveAmdZen1Cpu)
153 /* One 256-bit FMA per cycle makes 2xNN faster */
154 kernelSetup.kernelType = KernelType::Cpu4xN_Simd_2xNN;
156 #endif /* GMX_NBNXN_SIMD_2XNN && GMX_NBNXN_SIMD_4XN */
159 if (getenv("GMX_NBNXN_SIMD_4XN") != nullptr)
161 #ifdef GMX_NBNXN_SIMD_4XN
162 kernelSetup.kernelType = KernelType::Cpu4xN_Simd_4xN;
165 "SIMD 4xN kernels requested, but GROMACS has been compiled without support "
166 "for these kernels");
169 if (getenv("GMX_NBNXN_SIMD_2XNN") != nullptr)
171 #ifdef GMX_NBNXN_SIMD_2XNN
172 kernelSetup.kernelType = KernelType::Cpu4xN_Simd_2xNN;
175 "SIMD 2x(N+N) kernels requested, but GROMACS has been compiled without "
176 "support for these kernels");
180 /* Analytical Ewald exclusion correction is only an option in
182 * Since table lookup's don't parallelize with SIMD, analytical
183 * will probably always be faster for a SIMD width of 8 or more.
184 * With FMA analytical is sometimes faster for a width if 4 as well.
185 * In single precision, this is faster on Bulldozer.
186 * On AMD Zen, tabulated Ewald kernels are faster on all 4 combinations
187 * of single or double precision and 128 or 256-bit AVX2.
189 MSVC_DIAGNOSTIC_IGNORE(6285) // Always zero because compile time constant
192 (GMX_SIMD_REAL_WIDTH >= 8 || (GMX_SIMD_REAL_WIDTH >= 4 && GMX_SIMD_HAVE_FMA && !GMX_DOUBLE)) &&
194 !hardwareInfo.haveAmdZen1Cpu)
196 kernelSetup.ewaldExclusionType = EwaldExclusionType::Analytical;
198 MSVC_DIAGNOSTIC_RESET
199 else { 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(NbnxmGpu* 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 const t_inputrec* ir,
362 const t_forcerec* fr,
364 const gmx_hw_info_t& hardwareInfo,
365 const bool useGpuForNonbonded,
366 const gmx::DeviceStreamManager* deviceStreamManager,
367 const gmx_mtop_t* mtop,
369 gmx_wallcycle* wcycle)
371 const bool emulateGpu = (getenv("GMX_EMULATE_GPU") != nullptr);
373 GMX_RELEASE_ASSERT(!(emulateGpu && useGpuForNonbonded),
374 "When GPU emulation is active, there cannot be a GPU assignment");
376 NonbondedResource nonbondedResource;
377 if (useGpuForNonbonded)
379 nonbondedResource = NonbondedResource::Gpu;
383 nonbondedResource = NonbondedResource::EmulateGpu;
387 nonbondedResource = NonbondedResource::Cpu;
390 Nbnxm::KernelSetup kernelSetup = pick_nbnxn_kernel(mdlog, fr->use_simd_kernels, hardwareInfo,
391 nonbondedResource, ir, fr->bNonbonded);
393 const bool haveMultipleDomains = havePPDomainDecomposition(cr);
395 bool bFEP_NonBonded = (fr->efep != efepNO) && haveFepPerturbedNBInteractions(*mtop);
396 PairlistParams pairlistParams(kernelSetup.kernelType, bFEP_NonBonded, ir->rlist, haveMultipleDomains);
398 setupDynamicPairlistPruning(mdlog, ir, mtop, box, fr->ic, &pairlistParams);
400 int enbnxninitcombrule;
401 if (fr->ic->vdwtype == evdwCUT
402 && (fr->ic->vdw_modifier == eintmodNONE || fr->ic->vdw_modifier == eintmodPOTSHIFT)
403 && getenv("GMX_NO_LJ_COMB_RULE") == nullptr)
405 /* Plain LJ cut-off: we can optimize with combination rules */
406 enbnxninitcombrule = enbnxninitcombruleDETECT;
408 else if (fr->ic->vdwtype == evdwPME)
410 /* LJ-PME: we need to use a combination rule for the grid */
411 if (fr->ljpme_combination_rule == eljpmeGEOM)
413 enbnxninitcombrule = enbnxninitcombruleGEOM;
417 enbnxninitcombrule = enbnxninitcombruleLB;
422 /* We use a full combination matrix: no rule required */
423 enbnxninitcombrule = enbnxninitcombruleNONE;
426 auto pinPolicy = (useGpuForNonbonded ? gmx::PinningPolicy::PinnedIfSupported
427 : 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 (useGpuForNonbonded || emulateGpu) ? 1 : gmx_omp_nthreads_get(emntNonbonded));
444 NbnxmGpu* gpu_nbv = nullptr;
445 int minimumIlistCountForGpuBalancing = 0;
446 if (useGpuForNonbonded)
448 /* init the NxN GPU data; the last argument tells whether we'll have
449 * both local and non-local NB calculation on GPU */
451 (deviceStreamManager != nullptr),
452 "Device stream manager should be initialized in order to use GPU for non-bonded.");
453 gpu_nbv = gpu_init(*deviceStreamManager, fr->ic, pairlistParams, nbat.get(), haveMultipleDomains);
455 minimumIlistCountForGpuBalancing = getMinimumIlistCountForGpuBalancing(gpu_nbv);
458 auto pairlistSets = std::make_unique<PairlistSets>(pairlistParams, haveMultipleDomains,
459 minimumIlistCountForGpuBalancing);
461 auto pairSearch = std::make_unique<PairSearch>(
462 ir->pbcType, EI_TPI(ir->eI), DOMAINDECOMP(cr) ? &cr->dd->numCells : nullptr,
463 DOMAINDECOMP(cr) ? domdec_zones(cr->dd) : nullptr, pairlistParams.pairlistType,
464 bFEP_NonBonded, gmx_omp_nthreads_get(emntPairsearch), pinPolicy);
466 return std::make_unique<nonbonded_verlet_t>(std::move(pairlistSets), std::move(pairSearch),
467 std::move(nbat), kernelSetup, gpu_nbv, wcycle);
472 nonbonded_verlet_t::nonbonded_verlet_t(std::unique_ptr<PairlistSets> pairlistSets,
473 std::unique_ptr<PairSearch> pairSearch,
474 std::unique_ptr<nbnxn_atomdata_t> nbat_in,
475 const Nbnxm::KernelSetup& kernelSetup,
476 NbnxmGpu* gpu_nbv_ptr,
477 gmx_wallcycle* wcycle) :
478 pairlistSets_(std::move(pairlistSets)),
479 pairSearch_(std::move(pairSearch)),
480 nbat(std::move(nbat_in)),
481 kernelSetup_(kernelSetup),
485 GMX_RELEASE_ASSERT(pairlistSets_, "Need valid pairlistSets");
486 GMX_RELEASE_ASSERT(pairSearch_, "Need valid search object");
487 GMX_RELEASE_ASSERT(nbat, "Need valid atomdata object");
490 nonbonded_verlet_t::~nonbonded_verlet_t()
492 Nbnxm::gpu_free(gpu_nbv);