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39 #include "gmx_omp_nthreads.h"
47 #include "gromacs/gmxlib/network.h"
48 #include "gromacs/mdtypes/commrec.h"
49 #include "gromacs/utility/cstringutil.h"
50 #include "gromacs/utility/enumerationhelpers.h"
51 #include "gromacs/utility/fatalerror.h"
52 #include "gromacs/utility/gmxassert.h"
53 #include "gromacs/utility/gmxomp.h"
54 #include "gromacs/utility/logger.h"
55 #include "gromacs/utility/programcontext.h"
57 /** Structure with the number of threads for each OpenMP multi-threaded
58 * algorithmic module in mdrun. */
61 int gnth; /**< Global num. of threads per PP or PP+PME process/tMPI thread. */
62 int gnth_pme; /**< Global num. of threads per PME only process/tMPI thread. */
64 gmx::EnumerationArray<ModuleMultiThread, int> nth; /**< Number of threads for each module, indexed with module_nth_t */
65 bool initialized; /**< TRUE if the module as been initialized. */
66 } omp_module_nthreads_t;
68 /** Names of environment variables to set the per module number of threads.
70 * Indexed with the values of module_nth_t.
72 static const char* enumValueToEnvVariableString(ModuleMultiThread enumValue)
74 constexpr gmx::EnumerationArray<ModuleMultiThread, const char*> moduleMultiThreadEnvVariableNames = {
75 "GMX_DEFAULT_NUM_THREADS should never be set",
76 "GMX_DOMDEC_NUM_THREADS",
77 "GMX_PAIRSEARCH_NUM_THREADS",
78 "GMX_NONBONDED_NUM_THREADS",
79 "GMX_LISTED_FORCES_NUM_THREADS",
80 "GMX_PME_NUM_THREADS",
81 "GMX_UPDATE_NUM_THREADS",
82 "GMX_VSITE_NUM_THREADS",
83 "GMX_LINCS_NUM_THREADS",
84 "GMX_SETTLE_NUM_THREADS"
86 return moduleMultiThreadEnvVariableNames[enumValue];
89 /** Names of the modules. */
90 static const char* enumValueToString(ModuleMultiThread enumValue)
92 constexpr gmx::EnumerationArray<ModuleMultiThread, const char*> moduleMultiThreadNames = {
93 "default", "domain decomposition",
94 "pair search", "non-bonded",
99 return moduleMultiThreadNames[enumValue];
102 /** Number of threads for each algorithmic module.
104 * File-scope global variable that gets set once in pick_module_nthreads()
105 * and queried via gmx_omp_nthreads_get().
107 * All fields are initialized to 0 which should result in errors if
108 * the init call is omitted.
110 // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
111 static omp_module_nthreads_t modth = { 0, 0, { 0, 0, 0, 0, 0, 0, 0, 0, 0 }, FALSE };
114 /** Determine the number of threads for module \p mod.
116 * \p m takes values form the module_nth_t enum and maps these to the
117 * corresponding value in modth_env_var.
119 * Each number of threads per module takes the default value unless
120 * GMX_*_NUM_THERADS env var is set, case in which its value overrides
123 static void pick_module_nthreads(const gmx::MDLogger& mdlog, ModuleMultiThread m, gmx_bool bSepPME)
128 const bool bOMP = GMX_OPENMP;
130 /* The default should never be set through a GMX_*_NUM_THREADS env var
131 * as it's always equal with gnth. */
132 if (m == ModuleMultiThread::Default)
137 /* check the environment variable */
138 if ((env = getenv(enumValueToEnvVariableString(m))) != nullptr)
140 sscanf(env, "%d", &nth);
144 gmx_warning("%s=%d is set, but %s is compiled without OpenMP!",
145 enumValueToEnvVariableString(m),
147 gmx::getProgramContext().displayName());
150 /* with the verlet codepath, when any GMX_*_NUM_THREADS env var is set,
151 * OMP_NUM_THREADS also has to be set */
152 if (getenv("OMP_NUM_THREADS") == nullptr)
155 "%s=%d is set, the default number of threads also "
156 "needs to be set with OMP_NUM_THREADS!",
157 enumValueToEnvVariableString(m),
161 /* only babble if we are really overriding with a different value */
162 if ((bSepPME && m == ModuleMultiThread::Pme && nth != modth.gnth_pme) || (nth != modth.gnth))
164 GMX_LOG(mdlog.warning)
166 .appendTextFormatted("%s=%d set, overriding the default number of %s threads",
167 enumValueToString(m),
169 enumValueToEnvVariableString(m));
174 /* pick the global PME node nthreads if we are setting the number
175 * of threads in separate PME nodes */
176 nth = (bSepPME && m == ModuleMultiThread::Pme) ? modth.gnth_pme : modth.gnth;
179 gmx_omp_nthreads_set(m, nth);
182 void gmx_omp_nthreads_read_env(const gmx::MDLogger& mdlog, int* nthreads_omp)
185 gmx_bool bCommandLineSetNthreadsOMP = *nthreads_omp > 0;
188 GMX_RELEASE_ASSERT(nthreads_omp, "nthreads_omp must be a non-NULL pointer");
190 if ((env = getenv("OMP_NUM_THREADS")) != nullptr)
194 sscanf(env, "%d", &nt_omp);
197 gmx_fatal(FARGS, "OMP_NUM_THREADS is invalid: '%s'", env);
200 if (bCommandLineSetNthreadsOMP && nt_omp != *nthreads_omp)
203 "Environment variable OMP_NUM_THREADS (%d) and the number of threads "
204 "requested on the command line (%d) have different values. Either omit one, "
205 "or set them both to the same value.",
210 /* Setting the number of OpenMP threads. */
211 *nthreads_omp = nt_omp;
213 /* Output the results */
215 "\nThe number of OpenMP threads was set by environment variable OMP_NUM_THREADS to "
218 bCommandLineSetNthreadsOMP ? " (and the command-line setting agreed with that)" : "");
220 /* This prints once per simulation for multi-simulations,
221 * which might help diagnose issues with inhomogenous
223 GMX_LOG(mdlog.info).appendTextFormatted("%s", buffer);
226 /* This prints once per process for real MPI (i.e. once
227 * per debug file), and once per simulation for thread MPI
228 * (because of logic in the calling function). */
229 fputs(buffer, debug);
234 /*! \brief Helper function for parsing various input about the number
235 of OpenMP threads to use in various modules and deciding what to
237 static void manage_number_of_openmp_threads(const gmx::MDLogger& mdlog,
240 int nthreads_hw_avail,
241 int omp_nthreads_req,
242 int omp_nthreads_pme_req,
243 gmx_bool gmx_unused bThisNodePMEOnly,
244 int numRanksOnThisNode,
251 /* modth is shared among tMPI threads, so for thread safety, the
252 * detection is done on the master only. It is not thread-safe
253 * with multiple simulations, but that's anyway not supported by
260 GMX_UNUSED_VALUE(cr);
263 if (modth.initialized)
265 /* Just return if the initialization has already been
266 done. This could only happen if gmx_omp_nthreads_init() has
267 already been called. */
271 /* With full OpenMP support (verlet scheme) set the number of threads
272 * per process / default:
273 * - 1 if not compiled with OpenMP or
274 * - OMP_NUM_THREADS if the env. var is set, or
275 * - omp_nthreads_req = #of threads requested by the user on the mdrun
276 * command line, otherwise
277 * - take the max number of available threads and distribute them
278 * on the processes/tMPI threads.
279 * ~ The GMX_*_NUM_THREADS env var overrides the number of threads of
280 * the respective module and it has to be used in conjunction with
283 * The number of PME threads is equal to:
284 * - 1 if not compiled with OpenMP or
285 * - GMX_PME_NUM_THREADS if defined, otherwise
286 * - OMP_NUM_THREADS if defined, otherwise
290 if ((env = getenv("OMP_NUM_THREADS")) != nullptr)
292 if (!bOMP && (std::strncmp(env, "1", 1) != 0))
294 gmx_warning("OMP_NUM_THREADS is set, but %s was compiled without OpenMP support!",
295 gmx::getProgramContext().displayName());
299 nth = gmx_omp_get_max_threads();
302 else if (omp_nthreads_req > 0)
304 nth = omp_nthreads_req;
308 /* max available threads per node */
309 nth = nthreads_hw_avail;
311 /* divide the threads among the MPI ranks */
312 if (nth >= numRanksOnThisNode)
314 nth /= numRanksOnThisNode;
322 /* now we have the global values, set them:
323 * - 1 if not compiled with OpenMP
324 * - nth for the verlet scheme when compiled with OpenMP
337 if (omp_nthreads_pme_req > 0)
339 modth.gnth_pme = omp_nthreads_pme_req;
343 modth.gnth_pme = nth;
351 /* now set the per-module values */
352 modth.nth[ModuleMultiThread::Default] = modth.gnth;
353 pick_module_nthreads(mdlog, ModuleMultiThread::Domdec, bSepPME);
354 pick_module_nthreads(mdlog, ModuleMultiThread::Pairsearch, bSepPME);
355 pick_module_nthreads(mdlog, ModuleMultiThread::Nonbonded, bSepPME);
356 pick_module_nthreads(mdlog, ModuleMultiThread::Bonded, bSepPME);
357 pick_module_nthreads(mdlog, ModuleMultiThread::Pme, bSepPME);
358 pick_module_nthreads(mdlog, ModuleMultiThread::Update, bSepPME);
359 pick_module_nthreads(mdlog, ModuleMultiThread::VirtualSite, bSepPME);
360 pick_module_nthreads(mdlog, ModuleMultiThread::Lincs, bSepPME);
361 pick_module_nthreads(mdlog, ModuleMultiThread::Settle, bSepPME);
363 /* set the number of threads globally */
367 if (bThisNodePMEOnly)
369 gmx_omp_set_num_threads(modth.gnth_pme);
372 #endif /* GMX_THREAD_MPI */
374 gmx_omp_set_num_threads(nth);
378 modth.initialized = TRUE;
381 /*! \brief Report on the OpenMP settings that will be used */
382 static void reportOpenmpSettings(const gmx::MDLogger& mdlog, const t_commrec* cr, gmx_bool bOMP, gmx_bool bSepPME)
385 const char* mpi_str = "per tMPI thread";
387 const char* mpi_str = "per MPI process";
389 int nth_min, nth_max, nth_pme_min, nth_pme_max;
391 /* inform the user about the settings */
400 /* Get the min and max thread counts over the MPI ranks */
401 int buf_in[4], buf_out[4];
403 buf_in[0] = -modth.gnth;
404 buf_in[1] = modth.gnth;
405 buf_in[2] = -modth.gnth_pme;
406 buf_in[3] = modth.gnth_pme;
408 MPI_Allreduce(buf_in, buf_out, 4, MPI_INT, MPI_MAX, cr->mpi_comm_mysim);
410 nth_min = -buf_out[0];
411 nth_max = buf_out[1];
412 nth_pme_min = -buf_out[2];
413 nth_pme_max = buf_out[3];
418 nth_min = modth.gnth;
419 nth_max = modth.gnth;
420 nth_pme_min = modth.gnth_pme;
421 nth_pme_max = modth.gnth_pme;
425 if (nth_max == nth_min)
427 GMX_LOG(mdlog.warning)
428 .appendTextFormatted("Using %d OpenMP thread%s %s",
430 nth_min > 1 ? "s" : "",
431 cr->nnodes > 1 ? mpi_str : "");
435 GMX_LOG(mdlog.warning).appendTextFormatted("Using %d - %d OpenMP threads %s", nth_min, nth_max, mpi_str);
438 if (bSepPME && (nth_pme_min != nth_min || nth_pme_max != nth_max))
440 if (nth_pme_max == nth_pme_min)
442 GMX_LOG(mdlog.warning)
443 .appendTextFormatted("Using %d OpenMP thread%s %s for PME",
445 nth_pme_min > 1 ? "s" : "",
446 cr->nnodes > 1 ? mpi_str : "");
450 GMX_LOG(mdlog.warning)
451 .appendTextFormatted(
452 "Using %d - %d OpenMP threads %s for PME", nth_pme_min, nth_pme_max, mpi_str);
455 GMX_LOG(mdlog.warning);
458 void gmx_omp_nthreads_init(const gmx::MDLogger& mdlog,
460 int nthreads_hw_avail,
461 int numRanksOnThisNode,
462 int omp_nthreads_req,
463 int omp_nthreads_pme_req,
464 gmx_bool bThisNodePMEOnly)
468 const bool bOMP = GMX_OPENMP;
470 bSepPME = (thisRankHasDuty(cr, DUTY_PP) != thisRankHasDuty(cr, DUTY_PME));
472 manage_number_of_openmp_threads(mdlog,
477 omp_nthreads_pme_req,
482 /* Non-master threads have to wait for the OpenMP management to be
483 * done, so that code elsewhere that uses OpenMP can be certain
484 * the setup is complete. */
487 MPI_Barrier(cr->mpi_comm_mysim);
491 reportOpenmpSettings(mdlog, cr, bOMP, bSepPME);
494 int gmx_omp_nthreads_get(ModuleMultiThread mod)
496 if (mod < ModuleMultiThread::Default || mod >= ModuleMultiThread::Count)
498 /* invalid module queried */
503 return modth.nth[mod];
507 void gmx_omp_nthreads_set(ModuleMultiThread mod, int nthreads)
509 /* Catch an attempt to set the number of threads on an invalid
511 GMX_RELEASE_ASSERT(mod >= ModuleMultiThread::Default && mod < ModuleMultiThread::Count,
512 "Trying to set nthreads on invalid OpenMP module");
514 modth.nth[mod] = nthreads;