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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
] =
72 "GMX_DEFAULT_NUM_THREADS should never be set",
73 "GMX_DOMDEC_NUM_THREADS", "GMX_PAIRSEARCH_NUM_THREADS",
74 "GMX_NONBONDED_NUM_THREADS", "GMX_LISTED_FORCES_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(const gmx::MDLogger
&mdlog
, int m
,
111 gmx_bool bFullOmpSupport
,
117 const bool bOMP
= GMX_OPENMP
;
119 /* The default should never be set through a GMX_*_NUM_THREADS env var
120 * as it's always equal with gnth. */
121 if (m
== emntDefault
)
126 /* check the environment variable */
127 if ((env
= getenv(modth_env_var
[m
])) != nullptr)
129 sscanf(env
, "%d", &nth
);
131 // cppcheck-suppress knownConditionTrueFalse
134 gmx_warning("%s=%d is set, but %s is compiled without OpenMP!",
135 modth_env_var
[m
], nth
,
136 gmx::getProgramContext().displayName());
139 /* with the verlet codepath, when any GMX_*_NUM_THREADS env var is set,
140 * OMP_NUM_THREADS also has to be set */
141 if (bFullOmpSupport
&& getenv("OMP_NUM_THREADS") == nullptr)
143 gmx_warning("%s=%d is set, the default number of threads also "
144 "needs to be set with OMP_NUM_THREADS!",
145 modth_env_var
[m
], nth
);
148 /* with the group scheme warn if any env var except PME is set */
149 if (!bFullOmpSupport
)
153 gmx_warning("%s=%d is set, but OpenMP multithreading is not "
155 modth_env_var
[m
], nth
, mod_name
[m
]);
160 /* only babble if we are really overriding with a different value */
161 if ((bSepPME
&& m
== emntPME
&& nth
!= modth
.gnth_pme
) || (nth
!= modth
.gnth
))
163 GMX_LOG(mdlog
.warning
).asParagraph().appendTextFormatted(
164 "%s=%d set, overriding the default number of %s threads",
165 modth_env_var
[m
], nth
, mod_name
[m
]);
170 /* pick the global PME node nthreads if we are setting the number
171 * of threads in separate PME nodes */
172 nth
= (bSepPME
&& m
== emntPME
) ? modth
.gnth_pme
: modth
.gnth
;
175 gmx_omp_nthreads_set(m
, nth
);
178 void gmx_omp_nthreads_read_env(int *nthreads_omp
,
179 gmx_bool bIsSimMaster
)
182 gmx_bool bCommandLineSetNthreadsOMP
= *nthreads_omp
> 0;
185 GMX_RELEASE_ASSERT(nthreads_omp
, "nthreads_omp must be a non-NULL pointer");
187 if ((env
= getenv("OMP_NUM_THREADS")) != nullptr)
191 sscanf(env
, "%d", &nt_omp
);
194 gmx_fatal(FARGS
, "OMP_NUM_THREADS is invalid: '%s'", env
);
197 if (bCommandLineSetNthreadsOMP
&& nt_omp
!= *nthreads_omp
)
199 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
);
202 /* Setting the number of OpenMP threads. */
203 *nthreads_omp
= nt_omp
;
205 /* Output the results */
207 "The number of OpenMP threads was set by environment variable OMP_NUM_THREADS to %d%s\n",
209 bCommandLineSetNthreadsOMP
? " (and the command-line setting agreed with that)" : "");
212 /* This prints once per simulation for multi-simulations,
213 * which might help diagnose issues with inhomogenous
215 fputs(buffer
, stderr
);
219 /* This prints once per process for real MPI (i.e. once
220 * per debug file), and once per simulation for thread MPI
221 * (because of logic in the calling function). */
222 fputs(buffer
, debug
);
227 /*! \brief Helper function for parsing various input about the number
228 of OpenMP threads to use in various modules and deciding what to
230 static void manage_number_of_openmp_threads(const gmx::MDLogger
&mdlog
,
233 int nthreads_hw_avail
,
234 int omp_nthreads_req
,
235 int omp_nthreads_pme_req
,
236 gmx_bool gmx_unused bThisNodePMEOnly
,
237 gmx_bool bFullOmpSupport
,
245 /* modth is shared among tMPI threads, so for thread safety, the
246 * detection is done on the master only. It is not thread-safe
247 * with multiple simulations, but that's anyway not supported by
254 GMX_UNUSED_VALUE(cr
);
257 if (modth
.initialized
)
259 /* Just return if the initialization has already been
260 done. This could only happen if gmx_omp_nthreads_init() has
261 already been called. */
265 /* With full OpenMP support (verlet scheme) set the number of threads
266 * per process / default:
267 * - 1 if not compiled with OpenMP or
268 * - OMP_NUM_THREADS if the env. var is set, or
269 * - omp_nthreads_req = #of threads requested by the user on the mdrun
270 * command line, otherwise
271 * - take the max number of available threads and distribute them
272 * on the processes/tMPI threads.
273 * ~ The GMX_*_NUM_THREADS env var overrides the number of threads of
274 * the respective module and it has to be used in conjunction with
277 * With the group scheme OpenMP multithreading is only supported in PME,
278 * for all other modules nthreads is set to 1.
279 * The number of PME threads is equal to:
280 * - 1 if not compiled with OpenMP or
281 * - GMX_PME_NUM_THREADS if defined, otherwise
282 * - OMP_NUM_THREADS if defined, otherwise
286 if ((env
= getenv("OMP_NUM_THREADS")) != nullptr)
288 if (!bOMP
&& (std::strncmp(env
, "1", 1) != 0))
290 gmx_warning("OMP_NUM_THREADS is set, but %s was compiled without OpenMP support!",
291 gmx::getProgramContext().displayName());
295 nth
= gmx_omp_get_max_threads();
298 else if (omp_nthreads_req
> 0)
300 nth
= omp_nthreads_req
;
302 else if (bFullOmpSupport
&& bOMP
)
304 /* max available threads per node */
305 nth
= nthreads_hw_avail
;
307 /* divide the threads among the MPI processes/tMPI threads */
318 /* now we have the global values, set them:
319 * - 1 if not compiled with OpenMP and for the group scheme
320 * - nth for the verlet scheme when compiled with OpenMP
322 if (bFullOmpSupport
&& bOMP
)
333 if (omp_nthreads_pme_req
> 0)
335 modth
.gnth_pme
= omp_nthreads_pme_req
;
339 modth
.gnth_pme
= nth
;
347 /* now set the per-module values */
348 modth
.nth
[emntDefault
] = modth
.gnth
;
349 pick_module_nthreads(mdlog
, emntDomdec
, bFullOmpSupport
, bSepPME
);
350 pick_module_nthreads(mdlog
, emntPairsearch
, bFullOmpSupport
, bSepPME
);
351 pick_module_nthreads(mdlog
, emntNonbonded
, bFullOmpSupport
, bSepPME
);
352 pick_module_nthreads(mdlog
, emntBonded
, bFullOmpSupport
, bSepPME
);
353 pick_module_nthreads(mdlog
, emntPME
, bFullOmpSupport
, bSepPME
);
354 pick_module_nthreads(mdlog
, emntUpdate
, bFullOmpSupport
, bSepPME
);
355 pick_module_nthreads(mdlog
, emntVSITE
, bFullOmpSupport
, bSepPME
);
356 pick_module_nthreads(mdlog
, emntLINCS
, bFullOmpSupport
, bSepPME
);
357 pick_module_nthreads(mdlog
, emntSETTLE
, bFullOmpSupport
, bSepPME
);
359 /* set the number of threads globally */
363 if (bThisNodePMEOnly
)
365 gmx_omp_set_num_threads(modth
.gnth_pme
);
368 #endif /* GMX_THREAD_MPI */
372 gmx_omp_set_num_threads(nth
);
376 gmx_omp_set_num_threads(1);
381 modth
.initialized
= TRUE
;
384 /*! \brief Report on the OpenMP settings that will be used */
386 reportOpenmpSettings(const gmx::MDLogger
&mdlog
,
389 gmx_bool bFullOmpSupport
,
393 const char *mpi_str
= "per tMPI thread";
395 const char *mpi_str
= "per MPI process";
397 int nth_min
, nth_max
, nth_pme_min
, nth_pme_max
;
399 /* inform the user about the settings */
406 if (cr
->nnodes
+ cr
->npmenodes
> 1)
408 /* Get the min and max thread counts over the MPI ranks */
409 int buf_in
[4], buf_out
[4];
411 buf_in
[0] = -modth
.gnth
;
412 buf_in
[1] = modth
.gnth
;
413 buf_in
[2] = -modth
.gnth_pme
;
414 buf_in
[3] = modth
.gnth_pme
;
416 MPI_Allreduce(buf_in
, buf_out
, 4, MPI_INT
, MPI_MAX
, cr
->mpi_comm_mysim
);
418 nth_min
= -buf_out
[0];
419 nth_max
= buf_out
[1];
420 nth_pme_min
= -buf_out
[2];
421 nth_pme_max
= buf_out
[3];
426 nth_min
= modth
.gnth
;
427 nth_max
= modth
.gnth
;
428 nth_pme_min
= modth
.gnth_pme
;
429 nth_pme_max
= modth
.gnth_pme
;
432 /* for group scheme we print PME threads info only */
435 if (nth_max
== nth_min
)
437 GMX_LOG(mdlog
.warning
).appendTextFormatted(
438 "Using %d OpenMP thread%s %s",
439 nth_min
, nth_min
> 1 ? "s" : "",
440 cr
->nnodes
> 1 ? mpi_str
: "");
444 GMX_LOG(mdlog
.warning
).appendTextFormatted(
445 "Using %d - %d OpenMP threads %s",
446 nth_min
, nth_max
, mpi_str
);
449 if (bSepPME
&& (nth_pme_min
!= nth_min
|| nth_pme_max
!= nth_max
))
451 if (nth_pme_max
== nth_pme_min
)
453 GMX_LOG(mdlog
.warning
).appendTextFormatted(
454 "Using %d OpenMP thread%s %s for PME",
455 nth_pme_min
, nth_pme_min
> 1 ? "s" : "",
456 cr
->nnodes
> 1 ? mpi_str
: "");
460 GMX_LOG(mdlog
.warning
).appendTextFormatted(
461 "Using %d - %d OpenMP threads %s for PME",
462 nth_pme_min
, nth_pme_max
, mpi_str
);
465 GMX_LOG(mdlog
.warning
);
468 /*! \brief Detect and warn about oversubscription of cores.
470 * \todo This could probably live elsewhere, since it is not specifc
471 * to OpenMP, and only needs modth.gnth.
473 * \todo Enable this for separate PME nodes as well! */
475 issueOversubscriptionWarning(const gmx::MDLogger
&mdlog
,
477 int nthreads_hw_avail
,
481 char sbuf
[STRLEN
], sbuf1
[STRLEN
], sbuf2
[STRLEN
];
483 if (bSepPME
|| 0 != cr
->rank_pp_intranode
)
488 if (modth
.gnth
*nppn
> nthreads_hw_avail
)
490 sprintf(sbuf
, "threads");
497 sprintf(sbuf
, "thread-MPI threads");
499 sprintf(sbuf
, "MPI processes");
500 sprintf(sbuf1
, " per rank");
501 sprintf(sbuf2
, "On rank %d: o", cr
->sim_nodeid
);
505 GMX_LOG(mdlog
.warning
).asParagraph().appendTextFormatted(
506 "WARNING: %sversubscribing the available %d logical CPU cores%s with %d %s.\n"
507 " This will cause considerable performance loss!",
508 sbuf2
, nthreads_hw_avail
, sbuf1
, nppn
*modth
.gnth
, sbuf
);
512 void gmx_omp_nthreads_init(const gmx::MDLogger
&mdlog
, t_commrec
*cr
,
513 int nthreads_hw_avail
,
514 int omp_nthreads_req
,
515 int omp_nthreads_pme_req
,
516 gmx_bool bThisNodePMEOnly
,
517 gmx_bool bFullOmpSupport
)
522 const bool bOMP
= GMX_OPENMP
;
524 /* number of MPI processes/threads per physical node */
525 nppn
= cr
->nrank_intranode
;
527 bSepPME
= ( (cr
->duty
& DUTY_PP
) && !(cr
->duty
& DUTY_PME
)) ||
528 (!(cr
->duty
& DUTY_PP
) && (cr
->duty
& DUTY_PME
));
530 manage_number_of_openmp_threads(mdlog
, cr
, bOMP
,
532 omp_nthreads_req
, omp_nthreads_pme_req
,
533 bThisNodePMEOnly
, bFullOmpSupport
,
536 /* Non-master threads have to wait for the OpenMP management to be
537 * done, so that code elsewhere that uses OpenMP can be certain
538 * the setup is complete. */
541 MPI_Barrier(cr
->mpi_comm_mysim
);
545 reportOpenmpSettings(mdlog
, cr
, bOMP
, bFullOmpSupport
, bSepPME
);
546 issueOversubscriptionWarning(mdlog
, cr
, nthreads_hw_avail
, nppn
, bSepPME
);
549 int gmx_omp_nthreads_get(int mod
)
551 if (mod
< 0 || mod
>= emntNR
)
553 /* invalid module queried */
558 return modth
.nth
[mod
];
563 gmx_omp_nthreads_set(int mod
, int nthreads
)
565 /* Catch an attempt to set the number of threads on an invalid
567 GMX_RELEASE_ASSERT(mod
>= 0 && mod
< emntNR
, "Trying to set nthreads on invalid OpenMP module");
569 modth
.nth
[mod
] = nthreads
;