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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 static void pick_module_nthreads(const gmx::MDLogger
&mdlog
, int m
,
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!",
130 modth_env_var
[m
], nth
,
131 gmx::getProgramContext().displayName());
134 /* with the verlet codepath, when any GMX_*_NUM_THREADS env var is set,
135 * OMP_NUM_THREADS also has to be set */
136 if (getenv("OMP_NUM_THREADS") == nullptr)
138 gmx_warning("%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
).asParagraph().appendTextFormatted(
147 "%s=%d set, overriding the default number of %s threads",
148 modth_env_var
[m
], nth
, mod_name
[m
]);
153 /* pick the global PME node nthreads if we are setting the number
154 * of threads in separate PME nodes */
155 nth
= (bSepPME
&& m
== emntPME
) ? modth
.gnth_pme
: modth
.gnth
;
158 gmx_omp_nthreads_set(m
, nth
);
161 void gmx_omp_nthreads_read_env(const gmx::MDLogger
&mdlog
,
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
)
182 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
);
185 /* Setting the number of OpenMP threads. */
186 *nthreads_omp
= nt_omp
;
188 /* Output the results */
190 "\nThe number of OpenMP threads was set by environment variable OMP_NUM_THREADS to %d%s\n\n",
192 bCommandLineSetNthreadsOMP
? " (and the command-line setting agreed with that)" : "");
194 /* This prints once per simulation for multi-simulations,
195 * which might help diagnose issues with inhomogenous
197 GMX_LOG(mdlog
.info
).appendTextFormatted("%s", buffer
);
200 /* This prints once per process for real MPI (i.e. once
201 * per debug file), and once per simulation for thread MPI
202 * (because of logic in the calling function). */
203 fputs(buffer
, debug
);
208 /*! \brief Helper function for parsing various input about the number
209 of OpenMP threads to use in various modules and deciding what to
211 static void manage_number_of_openmp_threads(const gmx::MDLogger
&mdlog
,
214 int nthreads_hw_avail
,
215 int omp_nthreads_req
,
216 int omp_nthreads_pme_req
,
217 gmx_bool gmx_unused bThisNodePMEOnly
,
218 int numRanksOnThisNode
,
225 /* modth is shared among tMPI threads, so for thread safety, the
226 * detection is done on the master only. It is not thread-safe
227 * with multiple simulations, but that's anyway not supported by
234 GMX_UNUSED_VALUE(cr
);
237 if (modth
.initialized
)
239 /* Just return if the initialization has already been
240 done. This could only happen if gmx_omp_nthreads_init() has
241 already been called. */
245 /* With full OpenMP support (verlet scheme) set the number of threads
246 * per process / default:
247 * - 1 if not compiled with OpenMP or
248 * - OMP_NUM_THREADS if the env. var is set, or
249 * - omp_nthreads_req = #of threads requested by the user on the mdrun
250 * command line, otherwise
251 * - take the max number of available threads and distribute them
252 * on the processes/tMPI threads.
253 * ~ The GMX_*_NUM_THREADS env var overrides the number of threads of
254 * the respective module and it has to be used in conjunction with
257 * The number of PME threads is equal to:
258 * - 1 if not compiled with OpenMP or
259 * - GMX_PME_NUM_THREADS if defined, otherwise
260 * - OMP_NUM_THREADS if defined, otherwise
264 if ((env
= getenv("OMP_NUM_THREADS")) != nullptr)
266 if (!bOMP
&& (std::strncmp(env
, "1", 1) != 0))
268 gmx_warning("OMP_NUM_THREADS is set, but %s was compiled without OpenMP support!",
269 gmx::getProgramContext().displayName());
273 nth
= gmx_omp_get_max_threads();
276 else if (omp_nthreads_req
> 0)
278 nth
= omp_nthreads_req
;
282 /* max available threads per node */
283 nth
= nthreads_hw_avail
;
285 /* divide the threads among the MPI ranks */
286 if (nth
>= numRanksOnThisNode
)
288 nth
/= numRanksOnThisNode
;
296 /* now we have the global values, set them:
297 * - 1 if not compiled with OpenMP
298 * - nth for the verlet scheme when compiled with OpenMP
311 if (omp_nthreads_pme_req
> 0)
313 modth
.gnth_pme
= omp_nthreads_pme_req
;
317 modth
.gnth_pme
= nth
;
325 /* now set the per-module values */
326 modth
.nth
[emntDefault
] = modth
.gnth
;
327 pick_module_nthreads(mdlog
, emntDomdec
, bSepPME
);
328 pick_module_nthreads(mdlog
, emntPairsearch
, bSepPME
);
329 pick_module_nthreads(mdlog
, emntNonbonded
, bSepPME
);
330 pick_module_nthreads(mdlog
, emntBonded
, bSepPME
);
331 pick_module_nthreads(mdlog
, emntPME
, bSepPME
);
332 pick_module_nthreads(mdlog
, emntUpdate
, bSepPME
);
333 pick_module_nthreads(mdlog
, emntVSITE
, bSepPME
);
334 pick_module_nthreads(mdlog
, emntLINCS
, bSepPME
);
335 pick_module_nthreads(mdlog
, emntSETTLE
, bSepPME
);
337 /* set the number of threads globally */
341 if (bThisNodePMEOnly
)
343 gmx_omp_set_num_threads(modth
.gnth_pme
);
346 #endif /* GMX_THREAD_MPI */
348 gmx_omp_set_num_threads(nth
);
352 modth
.initialized
= TRUE
;
355 /*! \brief Report on the OpenMP settings that will be used */
357 reportOpenmpSettings(const gmx::MDLogger
&mdlog
,
363 const char *mpi_str
= "per tMPI thread";
365 const char *mpi_str
= "per MPI process";
367 int nth_min
, nth_max
, nth_pme_min
, nth_pme_max
;
369 /* inform the user about the settings */
378 /* Get the min and max thread counts over the MPI ranks */
379 int buf_in
[4], buf_out
[4];
381 buf_in
[0] = -modth
.gnth
;
382 buf_in
[1] = modth
.gnth
;
383 buf_in
[2] = -modth
.gnth_pme
;
384 buf_in
[3] = modth
.gnth_pme
;
386 MPI_Allreduce(buf_in
, buf_out
, 4, MPI_INT
, MPI_MAX
, cr
->mpi_comm_mysim
);
388 nth_min
= -buf_out
[0];
389 nth_max
= buf_out
[1];
390 nth_pme_min
= -buf_out
[2];
391 nth_pme_max
= buf_out
[3];
396 nth_min
= modth
.gnth
;
397 nth_max
= modth
.gnth
;
398 nth_pme_min
= modth
.gnth_pme
;
399 nth_pme_max
= modth
.gnth_pme
;
403 if (nth_max
== nth_min
)
405 GMX_LOG(mdlog
.warning
).appendTextFormatted(
406 "Using %d OpenMP thread%s %s",
407 nth_min
, nth_min
> 1 ? "s" : "",
408 cr
->nnodes
> 1 ? mpi_str
: "");
412 GMX_LOG(mdlog
.warning
).appendTextFormatted(
413 "Using %d - %d OpenMP threads %s",
414 nth_min
, nth_max
, mpi_str
);
417 if (bSepPME
&& (nth_pme_min
!= nth_min
|| nth_pme_max
!= nth_max
))
419 if (nth_pme_max
== nth_pme_min
)
421 GMX_LOG(mdlog
.warning
).appendTextFormatted(
422 "Using %d OpenMP thread%s %s for PME",
423 nth_pme_min
, nth_pme_min
> 1 ? "s" : "",
424 cr
->nnodes
> 1 ? mpi_str
: "");
428 GMX_LOG(mdlog
.warning
).appendTextFormatted(
429 "Using %d - %d OpenMP threads %s for PME",
430 nth_pme_min
, nth_pme_max
, mpi_str
);
433 GMX_LOG(mdlog
.warning
);
436 void gmx_omp_nthreads_init(const gmx::MDLogger
&mdlog
, t_commrec
*cr
,
437 int nthreads_hw_avail
,
438 int numRanksOnThisNode
,
439 int omp_nthreads_req
,
440 int omp_nthreads_pme_req
,
441 gmx_bool bThisNodePMEOnly
)
445 const bool bOMP
= GMX_OPENMP
;
447 bSepPME
= (thisRankHasDuty(cr
, DUTY_PP
) != thisRankHasDuty(cr
, DUTY_PME
));
449 manage_number_of_openmp_threads(mdlog
, cr
, bOMP
,
451 omp_nthreads_req
, omp_nthreads_pme_req
,
452 bThisNodePMEOnly
, numRanksOnThisNode
, bSepPME
);
454 /* Non-master threads have to wait for the OpenMP management to be
455 * done, so that code elsewhere that uses OpenMP can be certain
456 * the setup is complete. */
459 MPI_Barrier(cr
->mpi_comm_mysim
);
463 reportOpenmpSettings(mdlog
, cr
, bOMP
, bSepPME
);
466 int gmx_omp_nthreads_get(int mod
)
468 if (mod
< 0 || mod
>= emntNR
)
470 /* invalid module queried */
475 return modth
.nth
[mod
];
480 gmx_omp_nthreads_set(int mod
, int nthreads
)
482 /* Catch an attempt to set the number of threads on an invalid
484 GMX_RELEASE_ASSERT(mod
>= 0 && mod
< emntNR
, "Trying to set nthreads on invalid OpenMP module");
486 modth
.nth
[mod
] = nthreads
;