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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/fatalerror.h"
51 #include "gromacs/utility/gmxassert.h"
52 #include "gromacs/utility/gmxomp.h"
53 #include "gromacs/utility/logger.h"
54 #include "gromacs/utility/programcontext.h"
56 /** Structure with the number of threads for each OpenMP multi-threaded
57 * algorithmic module in mdrun. */
60 int gnth; /**< Global num. of threads per PP or PP+PME process/tMPI thread. */
61 int gnth_pme; /**< Global num. of threads per PME only process/tMPI thread. */
63 int nth[emntNR]; /**< Number of threads for each module, indexed with module_nth_t */
64 gmx_bool initialized; /**< TRUE if the module as been initialized. */
65 } omp_module_nthreads_t;
67 /** Names of environment variables to set the per module number of threads.
69 * Indexed with the values of module_nth_t.
71 static const char* modth_env_var[emntNR] = { "GMX_DEFAULT_NUM_THREADS should never be set",
72 "GMX_DOMDEC_NUM_THREADS",
73 "GMX_PAIRSEARCH_NUM_THREADS",
74 "GMX_NONBONDED_NUM_THREADS",
75 "GMX_LISTED_FORCES_NUM_THREADS",
76 "GMX_PME_NUM_THREADS",
77 "GMX_UPDATE_NUM_THREADS",
78 "GMX_VSITE_NUM_THREADS",
79 "GMX_LINCS_NUM_THREADS",
80 "GMX_SETTLE_NUM_THREADS" };
82 /** Names of the modules. */
83 static const char* mod_name[emntNR] = { "default", "domain decomposition",
84 "pair search", "non-bonded",
89 /** Number of threads for each algorithmic module.
91 * File-scope global variable that gets set once in pick_module_nthreads()
92 * and queried via gmx_omp_nthreads_get().
94 * All fields are initialized to 0 which should result in errors if
95 * the init call is omitted.
97 static omp_module_nthreads_t modth = { 0, 0, { 0, 0, 0, 0, 0, 0, 0, 0, 0 }, FALSE };
100 /** Determine the number of threads for module \p mod.
102 * \p m takes values form the module_nth_t enum and maps these to the
103 * corresponding value in modth_env_var.
105 * Each number of threads per module takes the default value unless
106 * GMX_*_NUM_THERADS env var is set, case in which its value overrides
109 static void pick_module_nthreads(const gmx::MDLogger& mdlog, int m, gmx_bool bSepPME)
114 const bool bOMP = GMX_OPENMP;
116 /* The default should never be set through a GMX_*_NUM_THREADS env var
117 * as it's always equal with gnth. */
118 if (m == emntDefault)
123 /* check the environment variable */
124 if ((env = getenv(modth_env_var[m])) != nullptr)
126 sscanf(env, "%d", &nth);
130 gmx_warning("%s=%d is set, but %s is compiled without OpenMP!",
133 gmx::getProgramContext().displayName());
136 /* with the verlet codepath, when any GMX_*_NUM_THREADS env var is set,
137 * OMP_NUM_THREADS also has to be set */
138 if (getenv("OMP_NUM_THREADS") == nullptr)
141 "%s=%d is set, the default number of threads also "
142 "needs to be set with OMP_NUM_THREADS!",
147 /* only babble if we are really overriding with a different value */
148 if ((bSepPME && m == emntPME && nth != modth.gnth_pme) || (nth != modth.gnth))
150 GMX_LOG(mdlog.warning)
152 .appendTextFormatted("%s=%d set, overriding the default number of %s threads",
160 /* pick the global PME node nthreads if we are setting the number
161 * of threads in separate PME nodes */
162 nth = (bSepPME && m == emntPME) ? modth.gnth_pme : modth.gnth;
165 gmx_omp_nthreads_set(m, nth);
168 void gmx_omp_nthreads_read_env(const gmx::MDLogger& mdlog, int* nthreads_omp)
171 gmx_bool bCommandLineSetNthreadsOMP = *nthreads_omp > 0;
174 GMX_RELEASE_ASSERT(nthreads_omp, "nthreads_omp must be a non-NULL pointer");
176 if ((env = getenv("OMP_NUM_THREADS")) != nullptr)
180 sscanf(env, "%d", &nt_omp);
183 gmx_fatal(FARGS, "OMP_NUM_THREADS is invalid: '%s'", env);
186 if (bCommandLineSetNthreadsOMP && nt_omp != *nthreads_omp)
189 "Environment variable OMP_NUM_THREADS (%d) and the number of threads "
190 "requested on the command line (%d) have different values. Either omit one, "
191 "or set them both to the same value.",
196 /* Setting the number of OpenMP threads. */
197 *nthreads_omp = nt_omp;
199 /* Output the results */
201 "\nThe number of OpenMP threads was set by environment variable OMP_NUM_THREADS to "
204 bCommandLineSetNthreadsOMP ? " (and the command-line setting agreed with that)" : "");
206 /* This prints once per simulation for multi-simulations,
207 * which might help diagnose issues with inhomogenous
209 GMX_LOG(mdlog.info).appendTextFormatted("%s", buffer);
212 /* This prints once per process for real MPI (i.e. once
213 * per debug file), and once per simulation for thread MPI
214 * (because of logic in the calling function). */
215 fputs(buffer, debug);
220 /*! \brief Helper function for parsing various input about the number
221 of OpenMP threads to use in various modules and deciding what to
223 static void manage_number_of_openmp_threads(const gmx::MDLogger& mdlog,
226 int nthreads_hw_avail,
227 int omp_nthreads_req,
228 int omp_nthreads_pme_req,
229 gmx_bool gmx_unused bThisNodePMEOnly,
230 int numRanksOnThisNode,
237 /* modth is shared among tMPI threads, so for thread safety, the
238 * detection is done on the master only. It is not thread-safe
239 * with multiple simulations, but that's anyway not supported by
246 GMX_UNUSED_VALUE(cr);
249 if (modth.initialized)
251 /* Just return if the initialization has already been
252 done. This could only happen if gmx_omp_nthreads_init() has
253 already been called. */
257 /* With full OpenMP support (verlet scheme) set the number of threads
258 * per process / default:
259 * - 1 if not compiled with OpenMP or
260 * - OMP_NUM_THREADS if the env. var is set, or
261 * - omp_nthreads_req = #of threads requested by the user on the mdrun
262 * command line, otherwise
263 * - take the max number of available threads and distribute them
264 * on the processes/tMPI threads.
265 * ~ The GMX_*_NUM_THREADS env var overrides the number of threads of
266 * the respective module and it has to be used in conjunction with
269 * The number of PME threads is equal to:
270 * - 1 if not compiled with OpenMP or
271 * - GMX_PME_NUM_THREADS if defined, otherwise
272 * - OMP_NUM_THREADS if defined, otherwise
276 if ((env = getenv("OMP_NUM_THREADS")) != nullptr)
278 if (!bOMP && (std::strncmp(env, "1", 1) != 0))
280 gmx_warning("OMP_NUM_THREADS is set, but %s was compiled without OpenMP support!",
281 gmx::getProgramContext().displayName());
285 nth = gmx_omp_get_max_threads();
288 else if (omp_nthreads_req > 0)
290 nth = omp_nthreads_req;
294 /* max available threads per node */
295 nth = nthreads_hw_avail;
297 /* divide the threads among the MPI ranks */
298 if (nth >= numRanksOnThisNode)
300 nth /= numRanksOnThisNode;
308 /* now we have the global values, set them:
309 * - 1 if not compiled with OpenMP
310 * - nth for the verlet scheme when compiled with OpenMP
323 if (omp_nthreads_pme_req > 0)
325 modth.gnth_pme = omp_nthreads_pme_req;
329 modth.gnth_pme = nth;
337 /* now set the per-module values */
338 modth.nth[emntDefault] = modth.gnth;
339 pick_module_nthreads(mdlog, emntDomdec, bSepPME);
340 pick_module_nthreads(mdlog, emntPairsearch, bSepPME);
341 pick_module_nthreads(mdlog, emntNonbonded, bSepPME);
342 pick_module_nthreads(mdlog, emntBonded, bSepPME);
343 pick_module_nthreads(mdlog, emntPME, bSepPME);
344 pick_module_nthreads(mdlog, emntUpdate, bSepPME);
345 pick_module_nthreads(mdlog, emntVSITE, bSepPME);
346 pick_module_nthreads(mdlog, emntLINCS, bSepPME);
347 pick_module_nthreads(mdlog, emntSETTLE, bSepPME);
349 /* set the number of threads globally */
353 if (bThisNodePMEOnly)
355 gmx_omp_set_num_threads(modth.gnth_pme);
358 #endif /* GMX_THREAD_MPI */
360 gmx_omp_set_num_threads(nth);
364 modth.initialized = TRUE;
367 /*! \brief Report on the OpenMP settings that will be used */
368 static void reportOpenmpSettings(const gmx::MDLogger& mdlog, const t_commrec* cr, gmx_bool bOMP, gmx_bool bSepPME)
371 const char* mpi_str = "per tMPI thread";
373 const char* mpi_str = "per MPI process";
375 int nth_min, nth_max, nth_pme_min, nth_pme_max;
377 /* inform the user about the settings */
386 /* Get the min and max thread counts over the MPI ranks */
387 int buf_in[4], buf_out[4];
389 buf_in[0] = -modth.gnth;
390 buf_in[1] = modth.gnth;
391 buf_in[2] = -modth.gnth_pme;
392 buf_in[3] = modth.gnth_pme;
394 MPI_Allreduce(buf_in, buf_out, 4, MPI_INT, MPI_MAX, cr->mpi_comm_mysim);
396 nth_min = -buf_out[0];
397 nth_max = buf_out[1];
398 nth_pme_min = -buf_out[2];
399 nth_pme_max = buf_out[3];
404 nth_min = modth.gnth;
405 nth_max = modth.gnth;
406 nth_pme_min = modth.gnth_pme;
407 nth_pme_max = modth.gnth_pme;
411 if (nth_max == nth_min)
413 GMX_LOG(mdlog.warning)
414 .appendTextFormatted("Using %d OpenMP thread%s %s",
416 nth_min > 1 ? "s" : "",
417 cr->nnodes > 1 ? mpi_str : "");
421 GMX_LOG(mdlog.warning).appendTextFormatted("Using %d - %d OpenMP threads %s", nth_min, nth_max, mpi_str);
424 if (bSepPME && (nth_pme_min != nth_min || nth_pme_max != nth_max))
426 if (nth_pme_max == nth_pme_min)
428 GMX_LOG(mdlog.warning)
429 .appendTextFormatted("Using %d OpenMP thread%s %s for PME",
431 nth_pme_min > 1 ? "s" : "",
432 cr->nnodes > 1 ? mpi_str : "");
436 GMX_LOG(mdlog.warning)
437 .appendTextFormatted(
438 "Using %d - %d OpenMP threads %s for PME", nth_pme_min, nth_pme_max, mpi_str);
441 GMX_LOG(mdlog.warning);
444 void gmx_omp_nthreads_init(const gmx::MDLogger& mdlog,
446 int nthreads_hw_avail,
447 int numRanksOnThisNode,
448 int omp_nthreads_req,
449 int omp_nthreads_pme_req,
450 gmx_bool bThisNodePMEOnly)
454 const bool bOMP = GMX_OPENMP;
456 bSepPME = (thisRankHasDuty(cr, DUTY_PP) != thisRankHasDuty(cr, DUTY_PME));
458 manage_number_of_openmp_threads(mdlog,
463 omp_nthreads_pme_req,
468 /* Non-master threads have to wait for the OpenMP management to be
469 * done, so that code elsewhere that uses OpenMP can be certain
470 * the setup is complete. */
473 MPI_Barrier(cr->mpi_comm_mysim);
477 reportOpenmpSettings(mdlog, cr, bOMP, bSepPME);
480 int gmx_omp_nthreads_get(int mod)
482 if (mod < 0 || mod >= emntNR)
484 /* invalid module queried */
489 return modth.nth[mod];
493 void gmx_omp_nthreads_set(int mod, int nthreads)
495 /* Catch an attempt to set the number of threads on an invalid
497 GMX_RELEASE_ASSERT(mod >= 0 && mod < emntNR, "Trying to set nthreads on invalid OpenMP module");
499 modth.nth[mod] = nthreads;