303 lines
8.2 KiB
C
303 lines
8.2 KiB
C
/* Copyright (C) 2005-2018 Free Software Foundation, Inc.
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Contributed by Richard Henderson <rth@redhat.com>.
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This file is part of the GNU Offloading and Multi Processing Library
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(libgomp).
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Libgomp is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3, or (at your option)
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any later version.
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Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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/* This file handles the (bare) PARALLEL construct. */
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#include "libgomp.h"
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#include <limits.h>
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/* Determine the number of threads to be launched for a PARALLEL construct.
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This algorithm is explicitly described in OpenMP 3.0 section 2.4.1.
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SPECIFIED is a combination of the NUM_THREADS clause and the IF clause.
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If the IF clause is false, SPECIFIED is forced to 1. When NUM_THREADS
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is not present, SPECIFIED is 0. */
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unsigned
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gomp_resolve_num_threads (unsigned specified, unsigned count)
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{
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struct gomp_thread *thr = gomp_thread ();
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struct gomp_task_icv *icv;
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unsigned threads_requested, max_num_threads, num_threads;
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unsigned long busy;
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struct gomp_thread_pool *pool;
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icv = gomp_icv (false);
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if (specified == 1)
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return 1;
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else if (thr->ts.active_level >= 1 && !icv->nest_var)
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return 1;
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else if (thr->ts.active_level >= gomp_max_active_levels_var)
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return 1;
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/* If NUM_THREADS not specified, use nthreads_var. */
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if (specified == 0)
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threads_requested = icv->nthreads_var;
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else
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threads_requested = specified;
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max_num_threads = threads_requested;
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/* If dynamic threads are enabled, bound the number of threads
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that we launch. */
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if (icv->dyn_var)
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{
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unsigned dyn = gomp_dynamic_max_threads ();
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if (dyn < max_num_threads)
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max_num_threads = dyn;
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/* Optimization for parallel sections. */
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if (count && count < max_num_threads)
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max_num_threads = count;
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}
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/* UINT_MAX stands for infinity. */
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if (__builtin_expect (icv->thread_limit_var == UINT_MAX, 1)
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|| max_num_threads == 1)
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return max_num_threads;
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/* The threads_busy counter lives in thread_pool, if there
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isn't a thread_pool yet, there must be just one thread
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in the contention group. If thr->team is NULL, this isn't
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nested parallel, so there is just one thread in the
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contention group as well, no need to handle it atomically. */
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pool = thr->thread_pool;
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if (thr->ts.team == NULL || pool == NULL)
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{
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num_threads = max_num_threads;
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if (num_threads > icv->thread_limit_var)
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num_threads = icv->thread_limit_var;
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if (pool)
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pool->threads_busy = num_threads;
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return num_threads;
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}
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#ifdef HAVE_SYNC_BUILTINS
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do
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{
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busy = pool->threads_busy;
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num_threads = max_num_threads;
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if (icv->thread_limit_var - busy + 1 < num_threads)
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num_threads = icv->thread_limit_var - busy + 1;
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}
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while (__sync_val_compare_and_swap (&pool->threads_busy,
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busy, busy + num_threads - 1)
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!= busy);
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#else
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gomp_mutex_lock (&gomp_managed_threads_lock);
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num_threads = max_num_threads;
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busy = pool->threads_busy;
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if (icv->thread_limit_var - busy + 1 < num_threads)
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num_threads = icv->thread_limit_var - busy + 1;
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pool->threads_busy += num_threads - 1;
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gomp_mutex_unlock (&gomp_managed_threads_lock);
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#endif
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return num_threads;
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}
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void
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GOMP_parallel_start (void (*fn) (void *), void *data, unsigned num_threads)
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{
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num_threads = gomp_resolve_num_threads (num_threads, 0);
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gomp_team_start (fn, data, num_threads, 0, gomp_new_team (num_threads));
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}
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void
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GOMP_parallel_end (void)
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{
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struct gomp_task_icv *icv = gomp_icv (false);
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if (__builtin_expect (icv->thread_limit_var != UINT_MAX, 0))
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{
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struct gomp_thread *thr = gomp_thread ();
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struct gomp_team *team = thr->ts.team;
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unsigned int nthreads = team ? team->nthreads : 1;
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gomp_team_end ();
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if (nthreads > 1)
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{
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/* If not nested, there is just one thread in the
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contention group left, no need for atomicity. */
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if (thr->ts.team == NULL)
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thr->thread_pool->threads_busy = 1;
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else
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{
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#ifdef HAVE_SYNC_BUILTINS
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__sync_fetch_and_add (&thr->thread_pool->threads_busy,
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1UL - nthreads);
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#else
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gomp_mutex_lock (&gomp_managed_threads_lock);
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thr->thread_pool->threads_busy -= nthreads - 1;
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gomp_mutex_unlock (&gomp_managed_threads_lock);
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#endif
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}
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}
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}
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else
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gomp_team_end ();
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}
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ialias (GOMP_parallel_end)
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void
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GOMP_parallel (void (*fn) (void *), void *data, unsigned num_threads, unsigned int flags)
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{
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num_threads = gomp_resolve_num_threads (num_threads, 0);
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gomp_team_start (fn, data, num_threads, flags, gomp_new_team (num_threads));
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fn (data);
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ialias_call (GOMP_parallel_end) ();
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}
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bool
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GOMP_cancellation_point (int which)
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{
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if (!gomp_cancel_var)
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return false;
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struct gomp_thread *thr = gomp_thread ();
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struct gomp_team *team = thr->ts.team;
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if (which & (GOMP_CANCEL_LOOP | GOMP_CANCEL_SECTIONS))
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{
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if (team == NULL)
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return false;
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return team->work_share_cancelled != 0;
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}
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else if (which & GOMP_CANCEL_TASKGROUP)
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{
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if (thr->task->taskgroup && thr->task->taskgroup->cancelled)
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return true;
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/* FALLTHRU into the GOMP_CANCEL_PARALLEL case,
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as #pragma omp cancel parallel also cancels all explicit
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tasks. */
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}
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if (team)
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return gomp_team_barrier_cancelled (&team->barrier);
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return false;
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}
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ialias (GOMP_cancellation_point)
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bool
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GOMP_cancel (int which, bool do_cancel)
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{
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if (!gomp_cancel_var)
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return false;
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if (!do_cancel)
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return ialias_call (GOMP_cancellation_point) (which);
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struct gomp_thread *thr = gomp_thread ();
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struct gomp_team *team = thr->ts.team;
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if (which & (GOMP_CANCEL_LOOP | GOMP_CANCEL_SECTIONS))
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{
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/* In orphaned worksharing region, all we want to cancel
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is current thread. */
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if (team != NULL)
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team->work_share_cancelled = 1;
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return true;
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}
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else if (which & GOMP_CANCEL_TASKGROUP)
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{
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if (thr->task->taskgroup && !thr->task->taskgroup->cancelled)
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{
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gomp_mutex_lock (&team->task_lock);
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thr->task->taskgroup->cancelled = true;
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gomp_mutex_unlock (&team->task_lock);
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}
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return true;
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}
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team->team_cancelled = 1;
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gomp_team_barrier_cancel (team);
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return true;
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}
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/* The public OpenMP API for thread and team related inquiries. */
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int
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omp_get_num_threads (void)
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{
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struct gomp_team *team = gomp_thread ()->ts.team;
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return team ? team->nthreads : 1;
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}
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int
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omp_get_thread_num (void)
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{
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return gomp_thread ()->ts.team_id;
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}
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/* This wasn't right for OpenMP 2.5. Active region used to be non-zero
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when the IF clause doesn't evaluate to false, starting with OpenMP 3.0
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it is non-zero with more than one thread in the team. */
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int
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omp_in_parallel (void)
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{
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return gomp_thread ()->ts.active_level > 0;
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}
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int
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omp_get_level (void)
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{
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return gomp_thread ()->ts.level;
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}
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int
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omp_get_ancestor_thread_num (int level)
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{
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struct gomp_team_state *ts = &gomp_thread ()->ts;
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if (level < 0 || level > ts->level)
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return -1;
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for (level = ts->level - level; level > 0; --level)
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ts = &ts->team->prev_ts;
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return ts->team_id;
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}
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int
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omp_get_team_size (int level)
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{
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struct gomp_team_state *ts = &gomp_thread ()->ts;
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if (level < 0 || level > ts->level)
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return -1;
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for (level = ts->level - level; level > 0; --level)
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ts = &ts->team->prev_ts;
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if (ts->team == NULL)
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return 1;
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else
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return ts->team->nthreads;
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}
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int
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omp_get_active_level (void)
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{
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return gomp_thread ()->ts.active_level;
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}
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ialias (omp_get_num_threads)
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ialias (omp_get_thread_num)
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ialias (omp_in_parallel)
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ialias (omp_get_level)
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ialias (omp_get_ancestor_thread_num)
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ialias (omp_get_team_size)
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ialias (omp_get_active_level)
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