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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 bool nbnxn_simd_supported(const gmx::MDLogger& mdlog, const t_inputrec& inputrec)
88 if (inputrec.vdwtype == VanDerWaalsType::Pme && inputrec.ljpme_combination_rule == LongRangeVdW::LB)
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& inputrec,
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(inputrec.coulombtype) || EVDW_PME(inputrec.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)
217 case KernelType::NotSet: return "not set";
218 case KernelType::Cpu4x4_PlainC: return "plain C";
219 case KernelType::Cpu4xN_Simd_4xN:
220 case KernelType::Cpu4xN_Simd_2xNN:
224 return "not available";
226 case KernelType::Gpu8x8x8: return "GPU";
227 case KernelType::Cpu8x8x8_PlainC: return "plain C";
229 default: gmx_fatal(FARGS, "Illegal kernel type selected");
233 /*! \brief Returns the most suitable kernel type and Ewald handling */
234 static KernelSetup pick_nbnxn_kernel(const gmx::MDLogger& mdlog,
235 gmx_bool use_simd_kernels,
236 const gmx_hw_info_t& hardwareInfo,
237 const NonbondedResource& nonbondedResource,
238 const t_inputrec& inputrec)
240 KernelSetup kernelSetup;
242 if (nonbondedResource == NonbondedResource::EmulateGpu)
244 kernelSetup.kernelType = KernelType::Cpu8x8x8_PlainC;
245 kernelSetup.ewaldExclusionType = EwaldExclusionType::DecidedByGpuModule;
247 GMX_LOG(mdlog.warning).asParagraph().appendText("Emulating a GPU run on the CPU (slow)");
249 else if (nonbondedResource == NonbondedResource::Gpu)
251 kernelSetup.kernelType = KernelType::Gpu8x8x8;
252 kernelSetup.ewaldExclusionType = EwaldExclusionType::DecidedByGpuModule;
256 if (use_simd_kernels && nbnxn_simd_supported(mdlog, inputrec))
258 kernelSetup = pick_nbnxn_kernel_cpu(inputrec, hardwareInfo);
262 kernelSetup.kernelType = KernelType::Cpu4x4_PlainC;
263 kernelSetup.ewaldExclusionType = EwaldExclusionType::Analytical;
269 .appendTextFormatted("Using %s %dx%d nonbonded short-range kernels",
270 lookup_kernel_name(kernelSetup.kernelType),
271 IClusterSizePerKernelType[kernelSetup.kernelType],
272 JClusterSizePerKernelType[kernelSetup.kernelType]);
274 if (KernelType::Cpu4x4_PlainC == kernelSetup.kernelType
275 || KernelType::Cpu8x8x8_PlainC == kernelSetup.kernelType)
277 GMX_LOG(mdlog.warning)
279 .appendTextFormatted(
280 "WARNING: Using the slow %s kernels. This should\n"
281 "not happen during routine usage on supported platforms.",
282 lookup_kernel_name(kernelSetup.kernelType));
285 GMX_RELEASE_ASSERT(kernelSetup.kernelType != KernelType::NotSet
286 && kernelSetup.ewaldExclusionType != EwaldExclusionType::NotSet,
287 "All kernel setup parameters should be set here");
294 PairlistSets::PairlistSets(const PairlistParams& pairlistParams,
295 const bool haveMultipleDomains,
296 const int minimumIlistCountForGpuBalancing) :
297 params_(pairlistParams),
298 minimumIlistCountForGpuBalancing_(minimumIlistCountForGpuBalancing)
300 localSet_ = std::make_unique<PairlistSet>(params_);
302 if (haveMultipleDomains)
304 nonlocalSet_ = std::make_unique<PairlistSet>(params_);
311 /*! \brief Gets and returns the minimum i-list count for balacing based on the GPU used or env.var. when set */
312 static int getMinimumIlistCountForGpuBalancing(NbnxmGpu* nbnxmGpu)
314 if (const char* env = getenv("GMX_NB_MIN_CI"))
318 int minimumIlistCount = strtol(env, &end, 10);
319 if (!end || (*end != 0) || minimumIlistCount < 0)
322 FARGS, "Invalid value passed in GMX_NB_MIN_CI=%s, non-negative integer required", env);
327 fprintf(debug, "Neighbor-list balancing parameter: %d (passed as env. var.)\n", minimumIlistCount);
329 return minimumIlistCount;
333 int minimumIlistCount = gpu_min_ci_balanced(nbnxmGpu);
337 "Neighbor-list balancing parameter: %d (auto-adjusted to the number of GPU "
338 "multi-processors)\n",
341 return minimumIlistCount;
345 static int getENbnxnInitCombRule(const t_forcerec& forcerec)
347 if (forcerec.ic->vdwtype == VanDerWaalsType::Cut
348 && (forcerec.ic->vdw_modifier == InteractionModifiers::None
349 || forcerec.ic->vdw_modifier == InteractionModifiers::PotShift)
350 && getenv("GMX_NO_LJ_COMB_RULE") == nullptr)
352 /* Plain LJ cut-off: we can optimize with combination rules */
353 return enbnxninitcombruleDETECT;
355 else if (forcerec.ic->vdwtype == VanDerWaalsType::Pme)
357 /* LJ-PME: we need to use a combination rule for the grid */
358 if (forcerec.ljpme_combination_rule == LongRangeVdW::Geom)
360 return enbnxninitcombruleGEOM;
364 return enbnxninitcombruleLB;
369 /* We use a full combination matrix: no rule required */
370 return enbnxninitcombruleNONE;
374 std::unique_ptr<nonbonded_verlet_t> init_nb_verlet(const gmx::MDLogger& mdlog,
375 const t_inputrec& inputrec,
376 const t_forcerec& forcerec,
377 const t_commrec* commrec,
378 const gmx_hw_info_t& hardwareInfo,
379 bool useGpuForNonbonded,
380 const gmx::DeviceStreamManager* deviceStreamManager,
381 const gmx_mtop_t& mtop,
383 gmx_wallcycle* wcycle)
385 const bool emulateGpu = (getenv("GMX_EMULATE_GPU") != nullptr);
387 GMX_RELEASE_ASSERT(!(emulateGpu && useGpuForNonbonded),
388 "When GPU emulation is active, there cannot be a GPU assignment");
390 NonbondedResource nonbondedResource;
391 if (useGpuForNonbonded)
393 nonbondedResource = NonbondedResource::Gpu;
397 nonbondedResource = NonbondedResource::EmulateGpu;
401 nonbondedResource = NonbondedResource::Cpu;
404 Nbnxm::KernelSetup kernelSetup = pick_nbnxn_kernel(
405 mdlog, forcerec.use_simd_kernels, hardwareInfo, nonbondedResource, inputrec);
407 const bool haveMultipleDomains = havePPDomainDecomposition(commrec);
409 bool bFEP_NonBonded = (forcerec.efep != FreeEnergyPerturbationType::No)
410 && haveFepPerturbedNBInteractions(mtop);
411 PairlistParams pairlistParams(
412 kernelSetup.kernelType, bFEP_NonBonded, inputrec.rlist, haveMultipleDomains);
414 setupDynamicPairlistPruning(mdlog, inputrec, mtop, box, *forcerec.ic, &pairlistParams);
416 const int enbnxninitcombrule = getENbnxnInitCombRule(forcerec);
418 auto pinPolicy = (useGpuForNonbonded ? gmx::PinningPolicy::PinnedIfSupported
419 : gmx::PinningPolicy::CannotBePinned);
421 auto nbat = std::make_unique<nbnxn_atomdata_t>(pinPolicy);
423 int mimimumNumEnergyGroupNonbonded = inputrec.opts.ngener;
424 if (inputrec.opts.ngener - inputrec.nwall == 1)
426 /* We have only one non-wall energy group, we do not need energy group
427 * support in the non-bondeds kernels, since all non-bonded energy
428 * contributions go to the first element of the energy group matrix.
430 mimimumNumEnergyGroupNonbonded = 1;
432 nbnxn_atomdata_init(mdlog,
434 kernelSetup.kernelType,
438 mimimumNumEnergyGroupNonbonded,
439 (useGpuForNonbonded || emulateGpu) ? 1 : gmx_omp_nthreads_get(emntNonbonded));
441 NbnxmGpu* gpu_nbv = nullptr;
442 int minimumIlistCountForGpuBalancing = 0;
443 if (useGpuForNonbonded)
445 /* init the NxN GPU data; the last argument tells whether we'll have
446 * both local and non-local NB calculation on GPU */
448 (deviceStreamManager != nullptr),
449 "Device stream manager should be initialized in order to use GPU for non-bonded.");
451 *deviceStreamManager, forcerec.ic, pairlistParams, nbat.get(), haveMultipleDomains);
453 minimumIlistCountForGpuBalancing = getMinimumIlistCountForGpuBalancing(gpu_nbv);
456 auto pairlistSets = std::make_unique<PairlistSets>(
457 pairlistParams, haveMultipleDomains, minimumIlistCountForGpuBalancing);
460 std::make_unique<PairSearch>(inputrec.pbcType,
462 DOMAINDECOMP(commrec) ? &commrec->dd->numCells : nullptr,
463 DOMAINDECOMP(commrec) ? domdec_zones(commrec->dd) : nullptr,
464 pairlistParams.pairlistType,
466 gmx_omp_nthreads_get(emntPairsearch),
469 return std::make_unique<nonbonded_verlet_t>(
470 std::move(pairlistSets), std::move(pairSearch), std::move(nbat), kernelSetup, gpu_nbv, wcycle);
475 nonbonded_verlet_t::nonbonded_verlet_t(std::unique_ptr<PairlistSets> pairlistSets,
476 std::unique_ptr<PairSearch> pairSearch,
477 std::unique_ptr<nbnxn_atomdata_t> nbat_in,
478 const Nbnxm::KernelSetup& kernelSetup,
479 NbnxmGpu* gpu_nbv_ptr,
480 gmx_wallcycle* wcycle) :
481 pairlistSets_(std::move(pairlistSets)),
482 pairSearch_(std::move(pairSearch)),
483 nbat(std::move(nbat_in)),
484 kernelSetup_(kernelSetup),
488 GMX_RELEASE_ASSERT(pairlistSets_, "Need valid pairlistSets");
489 GMX_RELEASE_ASSERT(pairSearch_, "Need valid search object");
490 GMX_RELEASE_ASSERT(nbat, "Need valid atomdata object");
493 nonbonded_verlet_t::~nonbonded_verlet_t()
495 Nbnxm::gpu_free(gpu_nbv);