sections.c revision 1.1.1.1.8.1 
1/* Copyright (C) 2005-2013 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
32static inline void
33gomp_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
68unsigned
69GOMP_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
106unsigned
107GOMP_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
133void
134GOMP_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
149void
150GOMP_sections_end (void)
151{
152  gomp_work_share_end ();
153}
154
155void
156GOMP_sections_end_nowait (void)
157{
158  gomp_work_share_end_nowait ();
159}
160