libgomp/sections.c

   1 /* Copyright (C) 2005, 2007, 2008, 2009 Free Software Foundation, Inc.
   2    Contributed by Richard Henderson <rth@redhat.com>.
   3
   4    This file is part of the GNU OpenMP Library (libgomp).
   5
   6    Libgomp is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3, or (at your option)
   9    any later version.
  10
  11    Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
  12    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  13    FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  14    more details.
  15
  16    Under Section 7 of GPL version 3, you are granted additional
  17    permissions described in the GCC Runtime Library Exception, version
  18    3.1, as published by the Free Software Foundation.
  19
  20    You should have received a copy of the GNU General Public License and
  21    a copy of the GCC Runtime Library Exception along with this program;
  22    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23    <http://www.gnu.org/licenses/>.  */
  24
  25 /* This file handles the SECTIONS construct.  */
  26
  27 #include "libgomp.h"
  28
  29
  30 /* Initialize the given work share construct from the given arguments.  */
  31
  32 static inline void
  33 gomp_sections_init (struct gomp_work_share *ws, unsigned count)
  34 {
  35   ws->sched = GFS_DYNAMIC;
  36   ws->chunk_size = 1;
  37   ws->end = count + 1;
  38   ws->incr = 1;
  39   ws->next = 1;
  40 }
  41
  42 /* This routine is called when first encountering a sections construct
  43    that is not bound directly to a parallel construct.  The first thread
  44    that arrives will create the work-share construct; subsequent threads
  45    will see the construct exists and allocate work from it.
  46
  47    COUNT is the number of sections in this construct.
  48
  49    Returns the 1-based section number for this thread to perform, or 0 if
  50    all work was assigned to other threads prior to this thread's arrival.  */
  51
  52 unsigned
  53 GOMP_sections_start (unsigned count)
  54 {
  55   struct gomp_thread *thr = gomp_thread ();
  56   long s, e, ret;
  57
  58   if (gomp_work_share_start (false))
  59     {
  60       gomp_sections_init (thr->ts.work_share, count);
  61       gomp_work_share_init_done ();
  62     }
  63
  64 #ifdef HAVE_SYNC_BUILTINS
  65   if (gomp_iter_dynamic_next (&s, &e))
  66     ret = s;
  67   else
  68     ret = 0;
  69 #else
  70   gomp_mutex_lock (&thr->ts.work_share->lock);
  71   if (gomp_iter_dynamic_next_locked (&s, &e))
  72     ret = s;
  73   else
  74     ret = 0;
  75   gomp_mutex_unlock (&thr->ts.work_share->lock);
  76 #endif
  77
  78   return ret;
  79 }
  80
  81 /* This routine is called when the thread completes processing of the
  82    section currently assigned to it.  If the work-share construct is
  83    bound directly to a parallel construct, then the construct may have
  84    been set up before the parallel.  In which case, this may be the
  85    first iteration for the thread.
  86
  87    Returns the 1-based section number for this thread to perform, or 0 if
  88    all work was assigned to other threads prior to this thread's arrival.  */
  89
  90 unsigned
  91 GOMP_sections_next (void)
  92 {
  93   long s, e, ret;
  94
  95 #ifdef HAVE_SYNC_BUILTINS
  96   if (gomp_iter_dynamic_next (&s, &e))
  97     ret = s;
  98   else
  99     ret = 0;
 100 #else
 101   struct gomp_thread *thr = gomp_thread ();
 102
 103   gomp_mutex_lock (&thr->ts.work_share->lock);
 104   if (gomp_iter_dynamic_next_locked (&s, &e))
 105     ret = s;
 106   else
 107     ret = 0;
 108   gomp_mutex_unlock (&thr->ts.work_share->lock);
 109 #endif
 110
 111   return ret;
 112 }
 113
 114 /* This routine pre-initializes a work-share construct to avoid one
 115    synchronization once we get into the loop.  */
 116
 117 void
 118 GOMP_parallel_sections_start (void (*fn) (void *), void *data,
 119                               unsigned num_threads, unsigned count)
 120 {
 121   struct gomp_team *team;
 122
 123   num_threads = gomp_resolve_num_threads (num_threads, count);
 124   team = gomp_new_team (num_threads);
 125   gomp_sections_init (&team->work_shares[0], count);
 126   gomp_team_start (fn, data, num_threads, team);
 127 }
 128
 129 /* The GOMP_section_end* routines are called after the thread is told
 130    that all sections are complete.  This first version synchronizes
 131    all threads; the nowait version does not.  */
 132
 133 void
 134 GOMP_sections_end (void)
 135 {
 136   gomp_work_share_end ();
 137 }
 138
 139 void
 140 GOMP_sections_end_nowait (void)
 141 {
 142   gomp_work_share_end_nowait ();
 143 }