src/gromacs/timing/walltime_accounting.cpp

   1 /*
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   4  * Copyright (c) 2013, The GROMACS development team.
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  36 #include "gmxpre.h"
  37
  38 #include "walltime_accounting.h"
  39
  40 #include "config.h"
  41
  42 #include <ctime>
  43
  44 #ifdef HAVE_UNISTD_H
  45 #include <unistd.h>
  46 #endif
  47 #ifdef HAVE_SYS_TIME_H
  48 #include <sys/time.h>
  49 #endif
  50
  51 #include "gromacs/utility/basedefinitions.h"
  52 #include "gromacs/utility/smalloc.h"
  53
  54 /* TODO in future: convert gmx_walltime_accounting to a class,
  55  * resolve who should have responsibility for recording the number of
  56  * steps done, consider whether parts of finish_time, print_perf,
  57  * wallcycle_print belong in this module.
  58  *
  59  * If/when any kind of task parallelism is implemented (even OpenMP
  60  * regions simultaneously assigned to different tasks), consider
  61  * whether this data structure (and/or cycle counters) should be
  62  * maintained on a per-OpenMP-thread basis. */
  63
  64 /*! \brief Manages caching wall-clock time measurements for
  65  * simulations */
  66 typedef struct gmx_walltime_accounting {
  67     //! Seconds since the epoch recorded at the start of the simulation
  68     double          start_time_stamp;
  69     //! Seconds since the epoch recorded at the start of the simulation for this thread
  70     double          start_time_stamp_per_thread;
  71     //! Total seconds elapsed over the simulation
  72     double          elapsed_time;
  73     //! Total seconds elapsed over the simulation running this thread
  74     double          elapsed_time_over_all_threads;
  75     /*! \brief Number of OpenMP threads that will be launched by this
  76      * MPI rank.
  77      *
  78      * This is used to scale elapsed_time_over_all_threads so
  79      * that any combination of real MPI, thread MPI and OpenMP (even
  80      * mdrun -ntomp_pme) processes/threads would (when run at maximum
  81      * efficiency) return values such that the sum of
  82      * elapsed_time_over_all_threads over all threads was constant
  83      * with respect to parallelism implementation. */
  84     int             numOpenMPThreads;
  85     //! Set by integrators to report the amount of work they did
  86     gmx_int64_t     nsteps_done;
  87 } t_gmx_walltime_accounting;
  88
  89 /*! \brief Calls system timing routines (e.g. clock_gettime) to get
  90  * the (fractional) number of seconds elapsed since the epoch when
  91  * this thread was executing.
  92  *
  93  * This can be used to measure system load. This can be unreliable if
  94  * threads migrate between sockets. If thread-specific timers are not
  95  * supported by the OS (e.g. if the OS is not POSIX-compliant), this
  96  * function is implemented by gmx_gettime. */
  97 static double gmx_gettime_per_thread();
  98
  99 // TODO In principle, all this should get protected by checks that
 100 // walltime_accounting is not null. In practice, that NULL condition
 101 // does not happen, and future refactoring will likely enforce it by
 102 // having the gmx_walltime_accounting_t object be owned by the runner
 103 // object. When these become member functions, existence will be
 104 // guaranteed.
 105
 106 gmx_walltime_accounting_t
 107 walltime_accounting_init(int numOpenMPThreads)
 108 {
 109     gmx_walltime_accounting_t walltime_accounting;
 110
 111     snew(walltime_accounting, 1);
 112     walltime_accounting->start_time_stamp            = 0;
 113     walltime_accounting->start_time_stamp_per_thread = 0;
 114     walltime_accounting->elapsed_time                = 0;
 115     walltime_accounting->nsteps_done                 = 0;
 116     walltime_accounting->numOpenMPThreads            = numOpenMPThreads;
 117
 118     return walltime_accounting;
 119 }
 120
 121 void
 122 walltime_accounting_destroy(gmx_walltime_accounting_t walltime_accounting)
 123 {
 124     sfree(walltime_accounting);
 125 }
 126
 127 void
 128 walltime_accounting_start(gmx_walltime_accounting_t walltime_accounting)
 129 {
 130     walltime_accounting->start_time_stamp            = gmx_gettime();
 131     walltime_accounting->start_time_stamp_per_thread = gmx_gettime_per_thread();
 132     walltime_accounting->elapsed_time                = 0;
 133     walltime_accounting->nsteps_done                 = 0;
 134 }
 135
 136 void
 137 walltime_accounting_end(gmx_walltime_accounting_t walltime_accounting)
 138 {
 139     double now, now_per_thread;
 140
 141     now            = gmx_gettime();
 142     now_per_thread = gmx_gettime_per_thread();
 143
 144     walltime_accounting->elapsed_time                  = now - walltime_accounting->start_time_stamp;
 145     walltime_accounting->elapsed_time_over_all_threads = now_per_thread - walltime_accounting->start_time_stamp_per_thread;
 146     /* For thread-MPI, the per-thread CPU timer makes this just
 147      * work. For OpenMP threads, the per-thread CPU timer measurement
 148      * needs to be multiplied by the number of OpenMP threads used,
 149      * under the current assumption that all regions ever opened
 150      * within a process are of the same size, and each thread should
 151      * keep one core busy.
 152      */
 153     walltime_accounting->elapsed_time_over_all_threads *= walltime_accounting->numOpenMPThreads;
 154 }
 155
 156 double
 157 walltime_accounting_get_current_elapsed_time(gmx_walltime_accounting_t walltime_accounting)
 158 {
 159     return gmx_gettime() - walltime_accounting->start_time_stamp;
 160 }
 161
 162 double
 163 walltime_accounting_get_elapsed_time(gmx_walltime_accounting_t walltime_accounting)
 164 {
 165     return walltime_accounting->elapsed_time;
 166 }
 167
 168 double
 169 walltime_accounting_get_elapsed_time_over_all_threads(gmx_walltime_accounting_t walltime_accounting)
 170 {
 171     return walltime_accounting->elapsed_time_over_all_threads;
 172 }
 173
 174 double
 175 walltime_accounting_get_start_time_stamp(gmx_walltime_accounting_t walltime_accounting)
 176 {
 177     return walltime_accounting->start_time_stamp;
 178 }
 179
 180 gmx_int64_t
 181 walltime_accounting_get_nsteps_done(gmx_walltime_accounting_t walltime_accounting)
 182 {
 183     return walltime_accounting->nsteps_done;
 184 }
 185
 186 void
 187 walltime_accounting_set_nsteps_done(gmx_walltime_accounting_t   walltime_accounting,
 188                                     gmx_int64_t                 nsteps_done)
 189 {
 190     walltime_accounting->nsteps_done = nsteps_done;
 191 }
 192
 193 double
 194 gmx_gettime()
 195 {
 196 #if defined HAVE_CLOCK_GETTIME && _POSIX_TIMERS >= 0 && !(defined __bgq__ && defined __clang__)
 197     /* Mac and Windows do not support this. For added fun, Windows
 198      * defines _POSIX_TIMERS without actually providing the
 199      * implementation. The BlueGene/Q CNK only supports gettimeofday,
 200      * and bgclang doesn't provide a fully functional implementation
 201      * for clock_gettime (unlike xlc). */
 202     struct timespec t;
 203     double          seconds;
 204
 205     clock_gettime(CLOCK_REALTIME, &t);
 206     seconds = static_cast<double>(t.tv_sec) + 1e-9*t.tv_nsec;
 207
 208     return seconds;
 209 #elif defined HAVE_GETTIMEOFDAY
 210     // Note that gettimeofday() is deprecated by POSIX, but since Mac
 211     // and Windows do not yet support POSIX, we are still stuck.
 212     // Also, this is the only supported API call on Bluegene/Q.
 213     struct timeval t;
 214     double         seconds;
 215
 216     gettimeofday(&t, NULL);
 217     seconds = static_cast<double>(t.tv_sec) + 1e-6*t.tv_usec;
 218
 219     return seconds;
 220 #else
 221     double  seconds;
 222
 223     seconds = time(NULL);
 224
 225     return seconds;
 226 #endif
 227 }
 228
 229 static double
 230 gmx_gettime_per_thread()
 231 {
 232 #if defined HAVE_CLOCK_GETTIME && _POSIX_THREAD_CPUTIME >= 0
 233     struct timespec t;
 234     double          seconds;
 235
 236     clock_gettime(CLOCK_THREAD_CPUTIME_ID, &t);
 237     seconds = static_cast<double>(t.tv_sec) + 1e-9*t.tv_nsec;
 238
 239     return seconds;
 240 #else
 241     return gmx_gettime();
 242 #endif
 243 }