libgomp/sections.c

   1 /* Copyright (C) 2005, 2007 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     gomp_sections_init (thr->ts.work_share, count);
  63
  64   if (gomp_iter_dynamic_next_locked (&s, &e))
  65     ret = s;
  66   else
  67     ret = 0;
  68
  69   gomp_mutex_unlock (&thr->ts.work_share->lock);
  70
  71   return ret;
  72 }
  73
  74 /* This routine is called when the thread completes processing of the
  75    section currently assigned to it.  If the work-share construct is
  76    bound directly to a parallel construct, then the construct may have
  77    been set up before the parallel.  In which case, this may be the
  78    first iteration for the thread.
  79
  80    Returns the 1-based section number for this thread to perform, or 0 if
  81    all work was assigned to other threads prior to this thread's arrival.  */
  82
  83 unsigned
  84 GOMP_sections_next (void)
  85 {
  86   struct gomp_thread *thr = gomp_thread ();
  87   long s, e, ret;
  88
  89   gomp_mutex_lock (&thr->ts.work_share->lock);
  90   if (gomp_iter_dynamic_next_locked (&s, &e))
  91     ret = s;
  92   else
  93     ret = 0;
  94   gomp_mutex_unlock (&thr->ts.work_share->lock);
  95
  96   return ret;
  97 }
  98
  99 /* This routine pre-initializes a work-share construct to avoid one
 100    synchronization once we get into the loop.  */
 101
 102 void
 103 GOMP_parallel_sections_start (void (*fn) (void *), void *data,
 104                               unsigned num_threads, unsigned count)
 105 {
 106   struct gomp_work_share *ws;
 107
 108   num_threads = gomp_resolve_num_threads (num_threads);
 109   if (gomp_dyn_var && num_threads > count)
 110     num_threads = count;
 111
 112   ws = gomp_new_work_share (false, num_threads);
 113   gomp_sections_init (ws, count);
 114   gomp_team_start (fn, data, num_threads, ws);
 115 }
 116
 117 /* The GOMP_section_end* routines are called after the thread is told
 118    that all sections are complete.  This first version synchronizes
 119    all threads; the nowait version does not.  */
 120
 121 void
 122 GOMP_sections_end (void)
 123 {
 124   gomp_work_share_end ();
 125 }
 126
 127 void
 128 GOMP_sections_end_nowait (void)
 129 {
 130   gomp_work_share_end_nowait ();
 131 }