libgomp/sections.c

   1 /* Copyright (C) 2005, 2007, 2008 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 Lesser General Public License as published by
   8    the Free Software Foundation; either version 2.1 of the License, or
   9    (at your option) 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 Lesser General Public License for
  14    more details.
  15
  16    You should have received a copy of the GNU Lesser General Public License
  17    along with libgomp; see the file COPYING.LIB.  If not, write to the
  18    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  19    MA 02110-1301, USA.  */
  20
  21 /* As a special exception, if you link this library with other files, some
  22    of which are compiled with GCC, to produce an executable, this library
  23    does not by itself cause the resulting executable to be covered by the
  24    GNU General Public License.  This exception does not however invalidate
  25    any other reasons why the executable file might be covered by the GNU
  26    General Public License.  */
  27
  28 /* This file handles the SECTIONS construct.  */
  29
  30 #include "libgomp.h"
  31
  32
  33 /* Initialize the given work share construct from the given arguments.  */
  34
  35 static inline void
  36 gomp_sections_init (struct gomp_work_share *ws, unsigned count)
  37 {
  38   ws->sched = GFS_DYNAMIC;
  39   ws->chunk_size = 1;
  40   ws->end = count + 1;
  41   ws->incr = 1;
  42   ws->next = 1;
  43 }
  44
  45 /* This routine is called when first encountering a sections construct
  46    that is not bound directly to a parallel construct.  The first thread
  47    that arrives will create the work-share construct; subsequent threads
  48    will see the construct exists and allocate work from it.
  49
  50    COUNT is the number of sections in this construct.
  51
  52    Returns the 1-based section number for this thread to perform, or 0 if
  53    all work was assigned to other threads prior to this thread's arrival.  */
  54
  55 unsigned
  56 GOMP_sections_start (unsigned count)
  57 {
  58   struct gomp_thread *thr = gomp_thread ();
  59   long s, e, ret;
  60
  61   if (gomp_work_share_start (false))
  62     {
  63       gomp_sections_init (thr->ts.work_share, count);
  64       gomp_work_share_init_done ();
  65     }
  66
  67 #ifdef HAVE_SYNC_BUILTINS
  68   if (gomp_iter_dynamic_next (&s, &e))
  69     ret = s;
  70   else
  71     ret = 0;
  72 #else
  73   gomp_mutex_lock (&thr->ts.work_share->lock);
  74   if (gomp_iter_dynamic_next_locked (&s, &e))
  75     ret = s;
  76   else
  77     ret = 0;
  78   gomp_mutex_unlock (&thr->ts.work_share->lock);
  79 #endif
  80
  81   return ret;
  82 }
  83
  84 /* This routine is called when the thread completes processing of the
  85    section currently assigned to it.  If the work-share construct is
  86    bound directly to a parallel construct, then the construct may have
  87    been set up before the parallel.  In which case, this may be the
  88    first iteration for the thread.
  89
  90    Returns the 1-based section number for this thread to perform, or 0 if
  91    all work was assigned to other threads prior to this thread's arrival.  */
  92
  93 unsigned
  94 GOMP_sections_next (void)
  95 {
  96   long s, e, ret;
  97
  98 #ifdef HAVE_SYNC_BUILTINS
  99   if (gomp_iter_dynamic_next (&s, &e))
 100     ret = s;
 101   else
 102     ret = 0;
 103 #else
 104   struct gomp_thread *thr = gomp_thread ();
 105
 106   gomp_mutex_lock (&thr->ts.work_share->lock);
 107   if (gomp_iter_dynamic_next_locked (&s, &e))
 108     ret = s;
 109   else
 110     ret = 0;
 111   gomp_mutex_unlock (&thr->ts.work_share->lock);
 112 #endif
 113
 114   return ret;
 115 }
 116
 117 /* This routine pre-initializes a work-share construct to avoid one
 118    synchronization once we get into the loop.  */
 119
 120 void
 121 GOMP_parallel_sections_start (void (*fn) (void *), void *data,
 122                               unsigned num_threads, unsigned count)
 123 {
 124   struct gomp_team *team;
 125
 126   num_threads = gomp_resolve_num_threads (num_threads, count);
 127   team = gomp_new_team (num_threads);
 128   gomp_sections_init (&team->work_shares[0], count);
 129   gomp_team_start (fn, data, num_threads, team);
 130 }
 131
 132 /* The GOMP_section_end* routines are called after the thread is told
 133    that all sections are complete.  This first version synchronizes
 134    all threads; the nowait version does not.  */
 135
 136 void
 137 GOMP_sections_end (void)
 138 {
 139   gomp_work_share_end ();
 140 }
 141
 142 void
 143 GOMP_sections_end_nowait (void)
 144 {
 145   gomp_work_share_end_nowait ();
 146 }