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45 #include "gmx_fatal.h"
50 #include "gmx_omp_nthreads.h"
51 #include "md_logging.h"
53 #include "gromacs/utility/gmxomp.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] =
72 "GMX_DEFAULT_NUM_THREADS should never be set",
73 "GMX_DOMDEC_NUM_THREADS", "GMX_PAIRSEARCH_NUM_THREADS",
74 "GMX_NONBONDED_NUM_THREADS", "GMX_BONDED_NUM_THREADS",
75 "GMX_PME_NUM_THREADS", "GMX_UPDATE_NUM_THREADS",
76 "GMX_VSITE_NUM_THREADS",
77 "GMX_LINCS_NUM_THREADS", "GMX_SETTLE_NUM_THREADS"
80 /** Names of the modules. */
81 static const char *mod_name[emntNR] =
83 "default", "domain decomposition", "pair search", "non-bonded",
84 "bonded", "PME", "update", "LINCS", "SETTLE"
87 /** Number of threads for each algorithmic module.
89 * File-scope global variable that gets set once in pick_module_nthreads()
90 * and queried via gmx_omp_nthreads_get().
92 * All fields are initialized to 0 which should result in errors if
93 * the init call is omitted.
95 static omp_module_nthreads_t modth = { 0, 0, {0, 0, 0, 0, 0, 0, 0, 0, 0}, FALSE};
98 /** Determine the number of threads for module \p mod.
100 * \p m takes values form the module_nth_t enum and maps these to the
101 * corresponding value in modth_env_var.
103 * Each number of threads per module takes the default value unless
104 * GMX_*_NUM_THERADS env var is set, case in which its value overrides
107 * The "group" scheme supports OpenMP only in PME and in thise case all but
108 * the PME nthread values default to 1.
110 static void pick_module_nthreads(FILE *fplog, int m,
112 gmx_bool bFullOmpSupport,
124 #endif /* GMX_OPENMP */
126 /* The default should never be set through a GMX_*_NUM_THREADS env var
127 * as it's always equal with gnth. */
128 if (m == emntDefault)
133 /* check the environment variable */
134 if ((env = getenv(modth_env_var[m])) != NULL)
136 sscanf(env, "%d", &nth);
140 gmx_warning("%s=%d is set, but %s is compiled without OpenMP!",
141 modth_env_var[m], nth, ShortProgram());
144 /* with the verlet codepath, when any GMX_*_NUM_THREADS env var is set,
145 * OMP_NUM_THREADS also has to be set */
146 if (bFullOmpSupport && getenv("OMP_NUM_THREADS") == NULL)
148 gmx_fatal(FARGS, "%s=%d is set, the default number of threads also "
149 "needs to be set with OMP_NUM_THREADS!",
150 modth_env_var[m], nth);
153 /* with the group scheme warn if any env var except PME is set */
154 if (!bFullOmpSupport)
158 gmx_warning("%s=%d is set, but OpenMP multithreading is not "
160 modth_env_var[m], nth, mod_name[m]);
165 /* only babble if we are really overriding with a different value */
166 if ((bSepPME && m == emntPME && nth != modth.gnth_pme) || (nth != modth.gnth))
168 sprintf(sbuf, "%s=%d set, overriding the default number of %s threads",
169 modth_env_var[m], nth, mod_name[m]);
172 fprintf(stderr, "\n%s\n", sbuf);
176 fprintf(fplog, "%s\n", sbuf);
182 /* pick the global PME node nthreads if we are setting the number
183 * of threads in separate PME nodes */
184 nth = (bSepPME && m == emntPME) ? modth.gnth_pme : modth.gnth;
187 gmx_omp_nthreads_set(m, nth);
190 void gmx_omp_nthreads_read_env(int *nthreads_omp,
191 gmx_bool bIsSimMaster)
194 gmx_bool bCommandLineSetNthreadsOMP = *nthreads_omp > 0;
197 assert(nthreads_omp);
199 if ((env = getenv("OMP_NUM_THREADS")) != NULL)
203 sscanf(env, "%d", &nt_omp);
206 gmx_fatal(FARGS, "OMP_NUM_THREADS is invalid: '%s'", env);
209 if (bCommandLineSetNthreadsOMP && nt_omp != *nthreads_omp)
211 gmx_fatal(FARGS, "Environment variable OMP_NUM_THREADS (%d) and the number of threads requested on the command line (%d) have different values. Either omit one, or set them both to the same value.", nt_omp, *nthreads_omp);
214 /* Setting the number of OpenMP threads. */
215 *nthreads_omp = nt_omp;
217 /* Output the results */
219 "The number of OpenMP threads was set by environment variable OMP_NUM_THREADS to %d%s\n",
221 bCommandLineSetNthreadsOMP ? " (and the command-line setting agreed with that)" : "");
224 /* This prints once per simulation for multi-simulations,
225 * which might help diagnose issues with inhomogenous
227 fputs(buffer, stderr);
231 /* This prints once per process for real MPI (i.e. once
232 * per debug file), and once per simulation for thread MPI
233 * (because of logic in the calling function). */
234 fputs(buffer, debug);
239 void gmx_omp_nthreads_init(FILE *fplog, t_commrec *cr,
240 int nthreads_hw_avail,
241 int omp_nthreads_req,
242 int omp_nthreads_pme_req,
243 gmx_bool gmx_unused bThisNodePMEOnly,
244 gmx_bool bFullOmpSupport)
246 int nth, nth_pmeonly, gmx_maxth, nppn;
248 gmx_bool bSepPME, bOMP;
254 #endif /* GMX_OPENMP */
256 /* number of MPI processes/threads per physical node */
257 nppn = cr->nrank_intranode;
259 bSepPME = ( (cr->duty & DUTY_PP) && !(cr->duty & DUTY_PME)) ||
260 (!(cr->duty & DUTY_PP) && (cr->duty & DUTY_PME));
262 #ifdef GMX_THREAD_MPI
263 /* modth is shared among tMPI threads, so for thread safety do the
264 * detection is done on the master only. It is not thread-safe with
265 * multiple simulations, but that's anyway not supported by tMPI. */
269 /* just return if the initialization has already been done */
270 if (modth.initialized)
275 /* With full OpenMP support (verlet scheme) set the number of threads
276 * per process / default:
277 * - 1 if not compiled with OpenMP or
278 * - OMP_NUM_THREADS if the env. var is set, or
279 * - omp_nthreads_req = #of threads requested by the user on the mdrun
280 * command line, otherwise
281 * - take the max number of available threads and distribute them
282 * on the processes/tMPI threads.
283 * ~ The GMX_*_NUM_THREADS env var overrides the number of threads of
284 * the respective module and it has to be used in conjunction with
287 * With the group scheme OpenMP multithreading is only supported in PME,
288 * for all other modules nthreads is set to 1.
289 * The number of PME threads is equal to:
290 * - 1 if not compiled with OpenMP or
291 * - GMX_PME_NUM_THREADS if defined, otherwise
292 * - OMP_NUM_THREADS if defined, otherwise
296 if ((env = getenv("OMP_NUM_THREADS")) != NULL)
298 if (!bOMP && (strncmp(env, "1", 1) != 0))
300 gmx_warning("OMP_NUM_THREADS is set, but %s was compiled without OpenMP support!",
305 nth = gmx_omp_get_max_threads();
308 else if (omp_nthreads_req > 0)
310 nth = omp_nthreads_req;
312 else if (bFullOmpSupport && bOMP)
314 /* max available threads per node */
315 nth = nthreads_hw_avail;
317 /* divide the threads among the MPI processes/tMPI threads */
328 /* now we have the global values, set them:
329 * - 1 if not compiled with OpenMP and for the group scheme
330 * - nth for the verlet scheme when compiled with OpenMP
332 if (bFullOmpSupport && bOMP)
343 if (omp_nthreads_pme_req > 0)
345 modth.gnth_pme = omp_nthreads_pme_req;
349 modth.gnth_pme = nth;
357 /* now set the per-module values */
358 modth.nth[emntDefault] = modth.gnth;
359 pick_module_nthreads(fplog, emntDomdec, SIMMASTER(cr), bFullOmpSupport, bSepPME);
360 pick_module_nthreads(fplog, emntPairsearch, SIMMASTER(cr), bFullOmpSupport, bSepPME);
361 pick_module_nthreads(fplog, emntNonbonded, SIMMASTER(cr), bFullOmpSupport, bSepPME);
362 pick_module_nthreads(fplog, emntBonded, SIMMASTER(cr), bFullOmpSupport, bSepPME);
363 pick_module_nthreads(fplog, emntPME, SIMMASTER(cr), bFullOmpSupport, bSepPME);
364 pick_module_nthreads(fplog, emntUpdate, SIMMASTER(cr), bFullOmpSupport, bSepPME);
365 pick_module_nthreads(fplog, emntVSITE, SIMMASTER(cr), bFullOmpSupport, bSepPME);
366 pick_module_nthreads(fplog, emntLINCS, SIMMASTER(cr), bFullOmpSupport, bSepPME);
367 pick_module_nthreads(fplog, emntSETTLE, SIMMASTER(cr), bFullOmpSupport, bSepPME);
369 /* set the number of threads globally */
372 #ifndef GMX_THREAD_MPI
373 if (bThisNodePMEOnly)
375 gmx_omp_set_num_threads(modth.gnth_pme);
378 #endif /* GMX_THREAD_MPI */
382 gmx_omp_set_num_threads(nth);
386 gmx_omp_set_num_threads(1);
391 modth.initialized = TRUE;
393 #ifdef GMX_THREAD_MPI
394 /* Non-master threads have to wait for the detection to be done. */
397 MPI_Barrier(cr->mpi_comm_mysim);
401 /* inform the user about the settings */
404 #ifdef GMX_THREAD_MPI
405 const char *mpi_str = "per tMPI thread";
407 const char *mpi_str = "per MPI process";
410 /* for group scheme we print PME threads info only */
413 md_print_info(cr, fplog, "Using %d OpenMP thread%s %s\n",
414 modth.gnth, modth.gnth > 1 ? "s" : "",
415 cr->nnodes > 1 ? mpi_str : "");
417 if (bSepPME && modth.gnth_pme != modth.gnth)
419 md_print_info(cr, fplog, "Using %d OpenMP thread%s %s for PME\n",
420 modth.gnth_pme, modth.gnth_pme > 1 ? "s" : "",
421 cr->nnodes > 1 ? mpi_str : "");
425 /* detect and warn about oversubscription
426 * TODO: enable this for separate PME nodes as well! */
427 if (!bSepPME && cr->rank_pp_intranode == 0)
429 char sbuf[STRLEN], sbuf1[STRLEN], sbuf2[STRLEN];
431 if (modth.gnth*nppn > nthreads_hw_avail)
433 sprintf(sbuf, "threads");
439 #ifdef GMX_THREAD_MPI
440 sprintf(sbuf, "thread-MPI threads");
442 sprintf(sbuf, "MPI processes");
443 sprintf(sbuf1, " per rank");
444 sprintf(sbuf2, "On rank %d: o", cr->sim_nodeid);
448 md_print_warn(cr, fplog,
449 "WARNING: %sversubscribing the available %d logical CPU cores%s with %d %s.\n"
450 " This will cause considerable performance loss!",
451 sbuf2, nthreads_hw_avail, sbuf1, nppn*modth.gnth, sbuf);
456 int gmx_omp_nthreads_get(int mod)
458 if (mod < 0 || mod >= emntNR)
460 /* invalid module queried */
465 return modth.nth[mod];
470 gmx_omp_nthreads_set(int mod, int nthreads)
472 /* Catch an attempt to set the number of threads on an invalid
474 assert(mod >= 0 && mod < emntNR);
476 modth.nth[mod] = nthreads;