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38 #include "gmx_omp_nthreads.h"
46 #include "gromacs/gmxlib/network.h"
47 #include "gromacs/mdtypes/commrec.h"
48 #include "gromacs/utility/cstringutil.h"
49 #include "gromacs/utility/fatalerror.h"
50 #include "gromacs/utility/gmxassert.h"
51 #include "gromacs/utility/gmxomp.h"
52 #include "gromacs/utility/logger.h"
53 #include "gromacs/utility/programcontext.h"
55 /** Structure with the number of threads for each OpenMP multi-threaded
56 * algorithmic module in mdrun. */
59 int gnth; /**< Global num. of threads per PP or PP+PME process/tMPI thread. */
60 int gnth_pme; /**< Global num. of threads per PME only process/tMPI thread. */
62 int nth[emntNR]; /**< Number of threads for each module, indexed with module_nth_t */
63 gmx_bool initialized; /**< TRUE if the module as been initialized. */
64 } omp_module_nthreads_t;
66 /** Names of environment variables to set the per module number of threads.
68 * Indexed with the values of module_nth_t.
70 static const char* modth_env_var[emntNR] = { "GMX_DEFAULT_NUM_THREADS should never be set",
71 "GMX_DOMDEC_NUM_THREADS",
72 "GMX_PAIRSEARCH_NUM_THREADS",
73 "GMX_NONBONDED_NUM_THREADS",
74 "GMX_LISTED_FORCES_NUM_THREADS",
75 "GMX_PME_NUM_THREADS",
76 "GMX_UPDATE_NUM_THREADS",
77 "GMX_VSITE_NUM_THREADS",
78 "GMX_LINCS_NUM_THREADS",
79 "GMX_SETTLE_NUM_THREADS" };
81 /** Names of the modules. */
82 static const char* mod_name[emntNR] = { "default", "domain decomposition",
83 "pair search", "non-bonded",
88 /** Number of threads for each algorithmic module.
90 * File-scope global variable that gets set once in pick_module_nthreads()
91 * and queried via gmx_omp_nthreads_get().
93 * All fields are initialized to 0 which should result in errors if
94 * the init call is omitted.
96 static omp_module_nthreads_t modth = { 0, 0, { 0, 0, 0, 0, 0, 0, 0, 0, 0 }, FALSE };
99 /** Determine the number of threads for module \p mod.
101 * \p m takes values form the module_nth_t enum and maps these to the
102 * corresponding value in modth_env_var.
104 * Each number of threads per module takes the default value unless
105 * GMX_*_NUM_THERADS env var is set, case in which its value overrides
108 static void pick_module_nthreads(const gmx::MDLogger& mdlog, int m, gmx_bool bSepPME)
113 const bool bOMP = GMX_OPENMP;
115 /* The default should never be set through a GMX_*_NUM_THREADS env var
116 * as it's always equal with gnth. */
117 if (m == emntDefault)
122 /* check the environment variable */
123 if ((env = getenv(modth_env_var[m])) != nullptr)
125 sscanf(env, "%d", &nth);
129 gmx_warning("%s=%d is set, but %s is compiled without OpenMP!", modth_env_var[m], nth,
130 gmx::getProgramContext().displayName());
133 /* with the verlet codepath, when any GMX_*_NUM_THREADS env var is set,
134 * OMP_NUM_THREADS also has to be set */
135 if (getenv("OMP_NUM_THREADS") == nullptr)
138 "%s=%d is set, the default number of threads also "
139 "needs to be set with OMP_NUM_THREADS!",
140 modth_env_var[m], nth);
143 /* only babble if we are really overriding with a different value */
144 if ((bSepPME && m == emntPME && nth != modth.gnth_pme) || (nth != modth.gnth))
146 GMX_LOG(mdlog.warning)
148 .appendTextFormatted("%s=%d set, overriding the default number of %s threads",
149 modth_env_var[m], nth, mod_name[m]);
154 /* pick the global PME node nthreads if we are setting the number
155 * of threads in separate PME nodes */
156 nth = (bSepPME && m == emntPME) ? modth.gnth_pme : modth.gnth;
159 gmx_omp_nthreads_set(m, nth);
162 void gmx_omp_nthreads_read_env(const gmx::MDLogger& mdlog, int* nthreads_omp)
165 gmx_bool bCommandLineSetNthreadsOMP = *nthreads_omp > 0;
168 GMX_RELEASE_ASSERT(nthreads_omp, "nthreads_omp must be a non-NULL pointer");
170 if ((env = getenv("OMP_NUM_THREADS")) != nullptr)
174 sscanf(env, "%d", &nt_omp);
177 gmx_fatal(FARGS, "OMP_NUM_THREADS is invalid: '%s'", env);
180 if (bCommandLineSetNthreadsOMP && nt_omp != *nthreads_omp)
183 "Environment variable OMP_NUM_THREADS (%d) and the number of threads "
184 "requested on the command line (%d) have different values. Either omit one, "
185 "or set them both to the same value.",
186 nt_omp, *nthreads_omp);
189 /* Setting the number of OpenMP threads. */
190 *nthreads_omp = nt_omp;
192 /* Output the results */
194 "\nThe number of OpenMP threads was set by environment variable OMP_NUM_THREADS to "
197 bCommandLineSetNthreadsOMP ? " (and the command-line setting agreed with that)" : "");
199 /* This prints once per simulation for multi-simulations,
200 * which might help diagnose issues with inhomogenous
202 GMX_LOG(mdlog.info).appendTextFormatted("%s", buffer);
205 /* This prints once per process for real MPI (i.e. once
206 * per debug file), and once per simulation for thread MPI
207 * (because of logic in the calling function). */
208 fputs(buffer, debug);
213 /*! \brief Helper function for parsing various input about the number
214 of OpenMP threads to use in various modules and deciding what to
216 static void manage_number_of_openmp_threads(const gmx::MDLogger& mdlog,
219 int nthreads_hw_avail,
220 int omp_nthreads_req,
221 int omp_nthreads_pme_req,
222 gmx_bool gmx_unused bThisNodePMEOnly,
223 int numRanksOnThisNode,
230 /* modth is shared among tMPI threads, so for thread safety, the
231 * detection is done on the master only. It is not thread-safe
232 * with multiple simulations, but that's anyway not supported by
239 GMX_UNUSED_VALUE(cr);
242 if (modth.initialized)
244 /* Just return if the initialization has already been
245 done. This could only happen if gmx_omp_nthreads_init() has
246 already been called. */
250 /* With full OpenMP support (verlet scheme) set the number of threads
251 * per process / default:
252 * - 1 if not compiled with OpenMP or
253 * - OMP_NUM_THREADS if the env. var is set, or
254 * - omp_nthreads_req = #of threads requested by the user on the mdrun
255 * command line, otherwise
256 * - take the max number of available threads and distribute them
257 * on the processes/tMPI threads.
258 * ~ The GMX_*_NUM_THREADS env var overrides the number of threads of
259 * the respective module and it has to be used in conjunction with
262 * The number of PME threads is equal to:
263 * - 1 if not compiled with OpenMP or
264 * - GMX_PME_NUM_THREADS if defined, otherwise
265 * - OMP_NUM_THREADS if defined, otherwise
269 if ((env = getenv("OMP_NUM_THREADS")) != nullptr)
271 if (!bOMP && (std::strncmp(env, "1", 1) != 0))
273 gmx_warning("OMP_NUM_THREADS is set, but %s was compiled without OpenMP support!",
274 gmx::getProgramContext().displayName());
278 nth = gmx_omp_get_max_threads();
281 else if (omp_nthreads_req > 0)
283 nth = omp_nthreads_req;
287 /* max available threads per node */
288 nth = nthreads_hw_avail;
290 /* divide the threads among the MPI ranks */
291 if (nth >= numRanksOnThisNode)
293 nth /= numRanksOnThisNode;
301 /* now we have the global values, set them:
302 * - 1 if not compiled with OpenMP
303 * - nth for the verlet scheme when compiled with OpenMP
316 if (omp_nthreads_pme_req > 0)
318 modth.gnth_pme = omp_nthreads_pme_req;
322 modth.gnth_pme = nth;
330 /* now set the per-module values */
331 modth.nth[emntDefault] = modth.gnth;
332 pick_module_nthreads(mdlog, emntDomdec, bSepPME);
333 pick_module_nthreads(mdlog, emntPairsearch, bSepPME);
334 pick_module_nthreads(mdlog, emntNonbonded, bSepPME);
335 pick_module_nthreads(mdlog, emntBonded, bSepPME);
336 pick_module_nthreads(mdlog, emntPME, bSepPME);
337 pick_module_nthreads(mdlog, emntUpdate, bSepPME);
338 pick_module_nthreads(mdlog, emntVSITE, bSepPME);
339 pick_module_nthreads(mdlog, emntLINCS, bSepPME);
340 pick_module_nthreads(mdlog, emntSETTLE, bSepPME);
342 /* set the number of threads globally */
346 if (bThisNodePMEOnly)
348 gmx_omp_set_num_threads(modth.gnth_pme);
351 #endif /* GMX_THREAD_MPI */
353 gmx_omp_set_num_threads(nth);
357 modth.initialized = TRUE;
360 /*! \brief Report on the OpenMP settings that will be used */
361 static void reportOpenmpSettings(const gmx::MDLogger& mdlog, const t_commrec* cr, gmx_bool bOMP, gmx_bool bSepPME)
364 const char* mpi_str = "per tMPI thread";
366 const char* mpi_str = "per MPI process";
368 int nth_min, nth_max, nth_pme_min, nth_pme_max;
370 /* inform the user about the settings */
379 /* Get the min and max thread counts over the MPI ranks */
380 int buf_in[4], buf_out[4];
382 buf_in[0] = -modth.gnth;
383 buf_in[1] = modth.gnth;
384 buf_in[2] = -modth.gnth_pme;
385 buf_in[3] = modth.gnth_pme;
387 MPI_Allreduce(buf_in, buf_out, 4, MPI_INT, MPI_MAX, cr->mpi_comm_mysim);
389 nth_min = -buf_out[0];
390 nth_max = buf_out[1];
391 nth_pme_min = -buf_out[2];
392 nth_pme_max = buf_out[3];
397 nth_min = modth.gnth;
398 nth_max = modth.gnth;
399 nth_pme_min = modth.gnth_pme;
400 nth_pme_max = modth.gnth_pme;
404 if (nth_max == nth_min)
406 GMX_LOG(mdlog.warning)
407 .appendTextFormatted("Using %d OpenMP thread%s %s", nth_min, nth_min > 1 ? "s" : "",
408 cr->nnodes > 1 ? mpi_str : "");
412 GMX_LOG(mdlog.warning).appendTextFormatted("Using %d - %d OpenMP threads %s", nth_min, nth_max, mpi_str);
415 if (bSepPME && (nth_pme_min != nth_min || nth_pme_max != nth_max))
417 if (nth_pme_max == nth_pme_min)
419 GMX_LOG(mdlog.warning)
420 .appendTextFormatted("Using %d OpenMP thread%s %s for PME", nth_pme_min,
421 nth_pme_min > 1 ? "s" : "", cr->nnodes > 1 ? mpi_str : "");
425 GMX_LOG(mdlog.warning)
426 .appendTextFormatted("Using %d - %d OpenMP threads %s for PME", nth_pme_min,
427 nth_pme_max, mpi_str);
430 GMX_LOG(mdlog.warning);
433 void gmx_omp_nthreads_init(const gmx::MDLogger& mdlog,
435 int nthreads_hw_avail,
436 int numRanksOnThisNode,
437 int omp_nthreads_req,
438 int omp_nthreads_pme_req,
439 gmx_bool bThisNodePMEOnly)
443 const bool bOMP = GMX_OPENMP;
445 bSepPME = (thisRankHasDuty(cr, DUTY_PP) != thisRankHasDuty(cr, DUTY_PME));
447 manage_number_of_openmp_threads(mdlog, cr, bOMP, nthreads_hw_avail, omp_nthreads_req,
448 omp_nthreads_pme_req, bThisNodePMEOnly, numRanksOnThisNode, bSepPME);
450 /* Non-master threads have to wait for the OpenMP management to be
451 * done, so that code elsewhere that uses OpenMP can be certain
452 * the setup is complete. */
455 MPI_Barrier(cr->mpi_comm_mysim);
459 reportOpenmpSettings(mdlog, cr, bOMP, bSepPME);
462 int gmx_omp_nthreads_get(int mod)
464 if (mod < 0 || mod >= emntNR)
466 /* invalid module queried */
471 return modth.nth[mod];
475 void gmx_omp_nthreads_set(int mod, int nthreads)
477 /* Catch an attempt to set the number of threads on an invalid
479 GMX_RELEASE_ASSERT(mod >= 0 && mod < emntNR, "Trying to set nthreads on invalid OpenMP module");
481 modth.nth[mod] = nthreads;