libgomp/sections.c

   1 /* Copyright (C) 2005, 2007, 2008, 2009, 2010 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 + 1L;
  38   ws->incr = 1;
  39   ws->next = 1;
  40 #ifdef HAVE_SYNC_BUILTINS
  41   /* Prepare things to make each iteration faster.  */
  42   if (sizeof (long) > sizeof (unsigned))
  43     ws->mode = 1;
  44   else
  45     {
  46       struct gomp_thread *thr = gomp_thread ();
  47       struct gomp_team *team = thr->ts.team;
  48       long nthreads = team ? team->nthreads : 1;
  49
  50       ws->mode = ((nthreads | ws->end)
  51                   < 1UL << (sizeof (long) * __CHAR_BIT__ / 2 - 1));
  52     }
  53 #else
  54   ws->mode = 0;
  55 #endif
  56 }
  57
  58 /* This routine is called when first encountering a sections construct
  59    that is not bound directly to a parallel construct.  The first thread
  60    that arrives will create the work-share construct; subsequent threads
  61    will see the construct exists and allocate work from it.
  62
  63    COUNT is the number of sections in this construct.
  64
  65    Returns the 1-based section number for this thread to perform, or 0 if
  66    all work was assigned to other threads prior to this thread's arrival.  */
  67
  68 unsigned
  69 GOMP_sections_start (unsigned count)
  70 {
  71   struct gomp_thread *thr = gomp_thread ();
  72   long s, e, ret;
  73
  74   if (gomp_work_share_start (false))
  75     {
  76       gomp_sections_init (thr->ts.work_share, count);
  77       gomp_work_share_init_done ();
  78     }
  79
  80 #ifdef HAVE_SYNC_BUILTINS
  81   if (gomp_iter_dynamic_next (&s, &e))
  82     ret = s;
  83   else
  84     ret = 0;
  85 #else
  86   gomp_mutex_lock (&thr->ts.work_share->lock);
  87   if (gomp_iter_dynamic_next_locked (&s, &e))
  88     ret = s;
  89   else
  90     ret = 0;
  91   gomp_mutex_unlock (&thr->ts.work_share->lock);
  92 #endif
  93
  94   return ret;
  95 }
  96
  97 /* This routine is called when the thread completes processing of the
  98    section currently assigned to it.  If the work-share construct is
  99    bound directly to a parallel construct, then the construct may have
 100    been set up before the parallel.  In which case, this may be the
 101    first iteration for the thread.
 102
 103    Returns the 1-based section number for this thread to perform, or 0 if
 104    all work was assigned to other threads prior to this thread's arrival.  */
 105
 106 unsigned
 107 GOMP_sections_next (void)
 108 {
 109   long s, e, ret;
 110
 111 #ifdef HAVE_SYNC_BUILTINS
 112   if (gomp_iter_dynamic_next (&s, &e))
 113     ret = s;
 114   else
 115     ret = 0;
 116 #else
 117   struct gomp_thread *thr = gomp_thread ();
 118
 119   gomp_mutex_lock (&thr->ts.work_share->lock);
 120   if (gomp_iter_dynamic_next_locked (&s, &e))
 121     ret = s;
 122   else
 123     ret = 0;
 124   gomp_mutex_unlock (&thr->ts.work_share->lock);
 125 #endif
 126
 127   return ret;
 128 }
 129
 130 /* This routine pre-initializes a work-share construct to avoid one
 131    synchronization once we get into the loop.  */
 132
 133 void
 134 GOMP_parallel_sections_start (void (*fn) (void *), void *data,
 135                               unsigned num_threads, unsigned count)
 136 {
 137   struct gomp_team *team;
 138
 139   num_threads = gomp_resolve_num_threads (num_threads, count);
 140   team = gomp_new_team (num_threads);
 141   gomp_sections_init (&team->work_shares[0], count);
 142   gomp_team_start (fn, data, num_threads, team);
 143 }
 144
 145 /* The GOMP_section_end* routines are called after the thread is told
 146    that all sections are complete.  This first version synchronizes
 147    all threads; the nowait version does not.  */
 148
 149 void
 150 GOMP_sections_end (void)
 151 {
 152   gomp_work_share_end ();
 153 }
 154
 155 void
 156 GOMP_sections_end_nowait (void)
 157 {
 158   gomp_work_share_end_nowait ();
 159 }