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45 #include "gmx_fatal.h"
51 #include "gmx_omp_nthreads.h"
52 #include "md_logging.h"
54 /** Structure with the number of threads for each OpenMP multi-threaded
55 * algorithmic module in mdrun. */
58 int gnth; /**< Global num. of threads per PP or PP+PME process/tMPI thread. */
59 int gnth_pme; /**< Global num. of threads per PME only process/tMPI thread. */
61 int nth[emntNR]; /**< Number of threads for each module, indexed with module_nth_t */
62 gmx_bool initialized; /**< TRUE if the module as been initialized. */
63 } omp_module_nthreads_t;
65 /** Names of environment variables to set the per module number of threads.
67 * Indexed with the values of module_nth_t.
69 static const char *modth_env_var[emntNR] =
71 "GMX_DEFAULT_NUM_THREADS should never be set",
72 "GMX_DOMDEC_NUM_THREADS", "GMX_PAIRSEARCH_NUM_THREADS",
73 "GMX_NONBONDED_NUM_THREADS", "GMX_BONDED_NUM_THREADS",
74 "GMX_PME_NUM_THREADS", "GMX_UPDATE_NUM_THREADS",
75 "GMX_VSITE_NUM_THREADS",
76 "GMX_LINCS_NUM_THREADS", "GMX_SETTLE_NUM_THREADS"
79 /** Names of the modules. */
80 static const char *mod_name[emntNR] =
82 "default", "domain decomposition", "pair search", "non-bonded",
83 "bonded", "PME", "update", "LINCS", "SETTLE"
86 /** Number of threads for each algorithmic module.
88 * File-scope global variable that gets set once in \init_module_nthreads
89 * and queried via gmx_omp_nthreads_get.
91 * All fields are initialized to 0 which should result in errors if
92 * the init call is omitted.
94 static omp_module_nthreads_t modth = { 0, 0, {0, 0, 0, 0, 0, 0, 0, 0, 0}, FALSE};
97 /** Determine the number of threads for module \mod.
99 * \m takes values form the module_nth_t enum and maps these to the
100 * corresponding value in modth_env_var.
102 * Each number of threads per module takes the default value unless
103 * GMX_*_NUM_THERADS env var is set, case in which its value overrides
106 * The "group" scheme supports OpenMP only in PME and in thise case all but
107 * the PME nthread values default to 1.
109 static int pick_module_nthreads(FILE *fplog, int m,
111 gmx_bool bFullOmpSupport,
123 #endif /* GMX_OPENMP */
125 /* The default should never be set through a GMX_*_NUM_THREADS env var
126 * as it's always equal with gnth. */
127 if (m == emntDefault)
129 return modth.nth[emntDefault];
132 /* check the environment variable */
133 if ((env = getenv(modth_env_var[m])) != NULL)
135 sscanf(env, "%d", &nth);
139 gmx_warning("%s=%d is set, but %s is compiled without OpenMP!",
140 modth_env_var[m], nth, ShortProgram());
143 /* with the verlet codepath, when any GMX_*_NUM_THREADS env var is set,
144 * OMP_NUM_THREADS also has to be set */
145 if (bFullOmpSupport && getenv("OMP_NUM_THREADS") == NULL)
147 gmx_fatal(FARGS, "%s=%d is set, the default number of threads also "
148 "needs to be set with OMP_NUM_THREADS!",
149 modth_env_var[m], nth);
152 /* with the group scheme warn if any env var except PME is set */
153 if (!bFullOmpSupport)
157 gmx_warning("%s=%d is set, but OpenMP multithreading is not "
159 modth_env_var[m], nth, mod_name[m]);
164 /* only babble if we are really overriding with a different value */
165 if ((bSepPME && m == emntPME && nth != modth.gnth_pme) || (nth != modth.gnth))
167 sprintf(sbuf, "%s=%d set, overriding the default number of %s threads",
168 modth_env_var[m], nth, mod_name[m]);
171 fprintf(stderr, "\n%s\n", sbuf);
175 fprintf(fplog, "%s\n", sbuf);
181 /* pick the global PME node nthreads if we are setting the number
182 * of threads in separate PME nodes */
183 nth = (bSepPME && m == emntPME) ? modth.gnth_pme : modth.gnth;
186 return modth.nth[m] = nth;
189 void gmx_omp_nthreads_read_env(int *nthreads_omp)
193 assert(nthreads_omp);
195 if ((env = getenv("OMP_NUM_THREADS")) != NULL)
199 sscanf(env,"%d",&nt_omp);
202 gmx_fatal(FARGS,"OMP_NUM_THREADS is invalid: '%s'",env);
205 if (*nthreads_omp > 0 && nt_omp != *nthreads_omp)
207 gmx_fatal(FARGS,"OMP_NUM_THREADS (%d) and the number of threads requested on the command line (%d) have different values",nt_omp,*nthreads_omp);
210 /* Setting the number of OpenMP threads.
211 * NOTE: with tMPI this function is only called on the master node,
212 * but with MPI on all nodes which means lots of messages on stderr.
214 fprintf(stderr,"Getting the number of OpenMP threads from OMP_NUM_THREADS: %d\n",nt_omp);
215 *nthreads_omp = nt_omp;
219 void gmx_omp_nthreads_init(FILE *fplog, t_commrec *cr,
220 int nthreads_hw_avail,
221 int omp_nthreads_req,
222 int omp_nthreads_pme_req,
223 gmx_bool bThisNodePMEOnly,
224 gmx_bool bFullOmpSupport)
226 int nth, nth_pmeonly, gmx_maxth, nppn;
228 gmx_bool bSepPME, bOMP;
234 #endif /* GMX_OPENMP */
236 /* number of processes per node */
237 nppn = cr->nnodes_intra;
239 bSepPME = ( (cr->duty & DUTY_PP) && !(cr->duty & DUTY_PME)) ||
240 (!(cr->duty & DUTY_PP) && (cr->duty & DUTY_PME));
242 #ifdef GMX_THREAD_MPI
243 /* modth is shared among tMPI threads, so for thread safety do the
244 * detection is done on the master only. It is not thread-safe with
245 * multiple simulations, but that's anyway not supported by tMPI. */
249 /* just return if the initialization has already been done */
250 if (modth.initialized)
255 /* With full OpenMP support (verlet scheme) set the number of threads
256 * per process / default:
257 * - 1 if not compiled with OpenMP or
258 * - OMP_NUM_THREADS if the env. var is set, or
259 * - omp_nthreads_req = #of threads requested by the user on the mdrun
260 * command line, otherwise
261 * - take the max number of available threads and distribute them
262 * on the processes/tMPI threads.
263 * ~ The GMX_*_NUM_THREADS env var overrides the number of threads of
264 * the respective module and it has to be used in conjunction with
267 * With the group scheme OpenMP multithreading is only supported in PME,
268 * for all other modules nthreads is set to 1.
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")) != NULL)
278 if (!bOMP && (strncmp(env, "1", 1) != 0))
280 gmx_warning("OMP_NUM_THREADS is set, but %s was compiled without OpenMP support!",
285 nth = gmx_omp_get_max_threads();
288 else if (omp_nthreads_req > 0)
290 nth = omp_nthreads_req;
292 else if (bFullOmpSupport && bOMP)
294 /* max available threads per node */
295 nth = nthreads_hw_avail;
297 /* divide the threads among the MPI processes/tMPI threads */
308 /* now we have the global values, set them:
309 * - 1 if not compiled with OpenMP and for the group scheme
310 * - nth for the verlet scheme when compiled with OpenMP
312 if (bFullOmpSupport && bOMP)
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(fplog, emntDomdec, SIMMASTER(cr), bFullOmpSupport, bSepPME);
340 pick_module_nthreads(fplog, emntPairsearch, SIMMASTER(cr), bFullOmpSupport, bSepPME);
341 pick_module_nthreads(fplog, emntNonbonded, SIMMASTER(cr), bFullOmpSupport, bSepPME);
342 pick_module_nthreads(fplog, emntBonded, SIMMASTER(cr), bFullOmpSupport, bSepPME);
343 pick_module_nthreads(fplog, emntPME, SIMMASTER(cr), bFullOmpSupport, bSepPME);
344 pick_module_nthreads(fplog, emntUpdate, SIMMASTER(cr), bFullOmpSupport, bSepPME);
345 pick_module_nthreads(fplog, emntVSITE, SIMMASTER(cr), bFullOmpSupport, bSepPME);
346 pick_module_nthreads(fplog, emntLINCS, SIMMASTER(cr), bFullOmpSupport, bSepPME);
347 pick_module_nthreads(fplog, emntSETTLE, SIMMASTER(cr), bFullOmpSupport, bSepPME);
349 /* set the number of threads globally */
352 #ifndef GMX_THREAD_MPI
353 if (bThisNodePMEOnly)
355 gmx_omp_set_num_threads(modth.gnth_pme);
358 #endif /* GMX_THREAD_MPI */
362 gmx_omp_set_num_threads(nth);
366 gmx_omp_set_num_threads(1);
371 modth.initialized = TRUE;
373 #ifdef GMX_THREAD_MPI
374 /* Non-master threads have to wait for the detection to be done. */
377 MPI_Barrier(cr->mpi_comm_mysim);
381 /* inform the user about the settings */
382 if (SIMMASTER(cr) && bOMP)
384 #ifdef GMX_THREAD_MPI
385 const char *mpi_str="per tMPI thread";
387 const char *mpi_str="per MPI process";
390 /* for group scheme we print PME threads info only */
393 fprintf(stderr, "Using %d OpenMP thread%s %s\n",
394 modth.gnth,modth.gnth > 1 ? "s" : "",
395 cr->nnodes > 1 ? mpi_str : "");
397 if (bSepPME && modth.gnth_pme != modth.gnth)
399 fprintf(stderr, "Using %d OpenMP thread%s %s for PME\n",
400 modth.gnth_pme,modth.gnth_pme > 1 ? "s" : "",
401 cr->nnodes > 1 ? mpi_str : "");
405 /* detect and warn about oversubscription
406 * TODO: enable this for separate PME nodes as well! */
407 if (!bSepPME && cr->nodeid_intra == 0)
409 char sbuf[STRLEN], sbuf1[STRLEN], sbuf2[STRLEN];
411 if (modth.gnth*nppn > nthreads_hw_avail)
413 sprintf(sbuf, "threads");
419 #ifdef GMX_THREAD_MPI
420 sprintf(sbuf, "thread-MPI threads");
422 sprintf(sbuf, "MPI processes");
423 sprintf(sbuf1, " per node");
424 sprintf(sbuf2, "On node %d: o", cr->sim_nodeid);
428 md_print_warn(cr, fplog,
429 "WARNING: %sversubscribing the available %d logical CPU cores%s with %d %s.\n"
430 " This will cause considerable performance loss!",
431 sbuf2, nthreads_hw_avail, sbuf1, nppn*modth.gnth, sbuf);
436 int gmx_omp_nthreads_get(int mod)
438 if (mod < 0 || mod >= emntNR)
440 /* invalid module queried */
445 return modth.nth[mod];