source: trunk/sys/libgomp/parallel.c @ 1

Last change on this file since 1 was 1, checked in by alain, 5 years ago

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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 (bare) PARALLEL construct.  */
26
27#include <gomp/libgomp.h>
28#include <limits.h>
29
30
31/* Determine the number of threads to be launched for a PARALLEL construct.
32   This algorithm is explicitly described in OpenMP 3.0 section 2.4.1.
33   SPECIFIED is a combination of the NUM_THREADS clause and the IF clause.
34   If the IF clause is false, SPECIFIED is forced to 1.  When NUM_THREADS
35   is not present, SPECIFIED is 0.  */
36
37unsigned
38gomp_resolve_num_threads (unsigned specified, unsigned count)
39{
40  struct gomp_thread *thread = gomp_thread();
41  struct gomp_task_icv *icv;
42  unsigned threads_requested, max_num_threads, num_threads;
43  unsigned long remaining;
44
45  icv = gomp_icv (false);
46
47  if (specified == 1)
48    return 1;
49  else if (thread->ts.active_level >= 1 && !icv->nest_var)
50    return 1;
51  else if (thread->ts.active_level >= gomp_max_active_levels_var)
52    return 1;
53
54  /* If NUM_THREADS not specified, use nthreads_var.  */
55  if (specified == 0)
56    threads_requested = icv->nthreads_var;
57  else
58    threads_requested = specified;
59
60  max_num_threads = threads_requested;
61
62  /* If dynamic threads are enabled, bound the number of threads
63     that we launch.  */
64  if (icv->dyn_var)
65    {
66      unsigned dyn = gomp_dynamic_max_threads ();
67      if (dyn < max_num_threads)
68        max_num_threads = dyn;
69
70      /* Optimization for parallel sections.  */
71      if (count && count < max_num_threads)
72        max_num_threads = count;
73    }
74
75  /* ULONG_MAX stands for infinity.  */
76  if (__builtin_expect (gomp_thread_limit_var == ULONG_MAX, 1)
77      || max_num_threads == 1)
78    return max_num_threads;
79
80#ifdef HAVE_SYNC_BUILTINS
81  do
82    {
83      remaining = gomp_remaining_threads_count;
84      num_threads = max_num_threads;
85      if (num_threads > remaining)
86        num_threads = remaining + 1;
87    }
88  while (__sync_val_compare_and_swap (&gomp_remaining_threads_count,
89                                      remaining, remaining - num_threads + 1)
90         != remaining);
91#else
92  gomp_mutex_lock (&gomp_remaining_threads_lock);
93  num_threads = max_num_threads;
94  remaining = gomp_remaining_threads_count;
95  if (num_threads > remaining)
96    num_threads = remaining + 1;
97  gomp_remaining_threads_count -= num_threads - 1;
98  gomp_mutex_unlock (&gomp_remaining_threads_lock);
99#endif
100
101  return num_threads;
102}
103
104void
105GOMP_parallel_start (void (*fn) (void *), void *data, unsigned num_threads)
106{
107  num_threads = gomp_resolve_num_threads (num_threads, 0);
108  gomp_team_start (fn, data, num_threads, gomp_new_team (num_threads));
109}
110
111void
112GOMP_parallel_end (void)
113{
114  if (__builtin_expect (gomp_thread_limit_var != ULONG_MAX, 0))
115    {
116      struct gomp_thread *thr = gomp_thread ();
117      struct gomp_team *team = thr->ts.team;
118      if (team && team->nthreads > 1)
119        {
120#ifdef HAVE_SYNC_BUILTINS
121          __sync_fetch_and_add (&gomp_remaining_threads_count,
122                                1UL - team->nthreads);
123#else
124          gomp_mutex_lock (&gomp_remaining_threads_lock);
125          gomp_remaining_threads_count -= team->nthreads - 1;
126#endif
127        }
128    }
129  gomp_team_end ();
130}
131
132
133/* The public OpenMP API for thread and team related inquiries.  */
134
135int
136omp_get_num_threads (void)
137{
138  struct gomp_team *team = gomp_thread ()->ts.team;
139  return team ? team->nthreads : 1;
140}
141
142int
143omp_get_thread_num (void)
144{
145  return gomp_thread ()->ts.team_id;
146}
147
148/* This wasn't right for OpenMP 2.5.  Active region used to be non-zero
149   when the IF clause doesn't evaluate to false, starting with OpenMP 3.0
150   it is non-zero with more than one thread in the team.  */
151
152int
153omp_in_parallel (void)
154{
155  return gomp_thread ()->ts.active_level > 0;
156}
157
158int
159omp_get_level (void)
160{
161  return gomp_thread ()->ts.level;
162}
163
164int
165omp_get_ancestor_thread_num (int level)
166{
167  struct gomp_team_state *ts = &gomp_thread ()->ts;
168  if (level < 0 || level > (int)ts->level)
169    return -1;
170  for (level = ts->level - level; level > 0; --level)
171    ts = &ts->team->prev_ts;
172  return ts->team_id;
173}
174
175int
176omp_get_team_size (int level)
177{
178  struct gomp_team_state *ts = &gomp_thread ()->ts;
179  if (level < 0 || level > (int)ts->level)
180    return -1;
181  for (level = ts->level - level; level > 0; --level)
182    ts = &ts->team->prev_ts;
183  if (ts->team == NULL)
184    return 1;
185  else
186    return ts->team->nthreads;
187}
188
189int
190omp_get_active_level (void)
191{
192  return gomp_thread ()->ts.active_level;
193}
194
195ialias (omp_get_num_threads)
196ialias (omp_get_thread_num)
197ialias (omp_in_parallel)
198ialias (omp_get_level)
199ialias (omp_get_ancestor_thread_num)
200ialias (omp_get_team_size)
201ialias (omp_get_active_level)
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