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+/* Copyright (C) 2005 Free Software Foundation, Inc.
+ Contributed by Richard Henderson <rth@redhat.com>.
+
+ This file is part of the GNU OpenMP Library (libgomp).
+
+ Libgomp is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
+ more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with libgomp; see the file COPYING.LIB. If not, write to the
+ Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ MA 02110-1301, USA. */
+
+/* As a special exception, if you link this library with other files, some
+ of which are compiled with GCC, to produce an executable, this library
+ does not by itself cause the resulting executable to be covered by the
+ GNU General Public License. This exception does not however invalidate
+ any other reasons why the executable file might be covered by the GNU
+ General Public License. */
+
+/* This file contains routines for managing work-share iteration, both
+ for loops and sections. */
+
+#include "libgomp.h"
+#include <stdlib.h>
+
+
+/* This function implements the STATIC scheduling method. The caller should
+ iterate *pstart <= x < *pend. Return zero if there are more iterations
+ to perform; nonzero if not. Return less than 0 if this thread had
+ received the absolutely last iteration. */
+
+int
+gomp_iter_static_next (long *pstart, long *pend)
+{
+ struct gomp_thread *thr = gomp_thread ();
+ struct gomp_team *team = thr->ts.team;
+ struct gomp_work_share *ws = thr->ts.work_share;
+ unsigned long nthreads = team ? team->nthreads : 1;
+
+ if (thr->ts.static_trip == -1)
+ return -1;
+
+ /* Quick test for degenerate teams and orphaned constructs. */
+ if (nthreads == 1)
+ {
+ *pstart = ws->next;
+ *pend = ws->end;
+ thr->ts.static_trip = -1;
+ return ws->next == ws->end;
+ }
+
+ /* We interpret chunk_size zero as "unspecified", which means that we
+ should break up the iterations such that each thread makes only one
+ trip through the outer loop. */
+ if (ws->chunk_size == 0)
+ {
+ unsigned long n, q, i;
+ unsigned long s0, e0;
+ long s, e;
+
+ if (thr->ts.static_trip > 0)
+ return 1;
+
+ /* Compute the total number of iterations. */
+ s = ws->incr + (ws->incr > 0 ? -1 : 1);
+ n = (ws->end - ws->next + s) / ws->incr;
+ i = thr->ts.team_id;
+
+ /* Compute the "zero-based" start and end points. That is, as
+ if the loop began at zero and incremented by one. */
+ q = n / nthreads;
+ q += (q * nthreads != n);
+ s0 = q * i;
+ e0 = s0 + q;
+ if (e0 > n)
+ e0 = n;
+
+ /* Notice when no iterations allocated for this thread. */
+ if (s0 >= e0)
+ {
+ thr->ts.static_trip = 1;
+ return 1;
+ }
+
+ /* Transform these to the actual start and end numbers. */
+ s = (long)s0 * ws->incr + ws->next;
+ e = (long)e0 * ws->incr + ws->next;
+
+ *pstart = s;
+ *pend = e;
+ thr->ts.static_trip = (e0 == n ? -1 : 1);
+ return 0;
+ }
+ else
+ {
+ unsigned long n, s0, e0, i, c;
+ long s, e;
+
+ /* Otherwise, each thread gets exactly chunk_size iterations
+ (if available) each time through the loop. */
+
+ s = ws->incr + (ws->incr > 0 ? -1 : 1);
+ n = (ws->end - ws->next + s) / ws->incr;
+ i = thr->ts.team_id;
+ c = ws->chunk_size;
+
+ /* Initial guess is a C sized chunk positioned nthreads iterations
+ in, offset by our thread number. */
+ s0 = (thr->ts.static_trip * nthreads + i) * c;
+ e0 = s0 + c;
+
+ /* Detect overflow. */
+ if (s0 >= n)
+ return 1;
+ if (e0 > n)
+ e0 = n;
+
+ /* Transform these to the actual start and end numbers. */
+ s = (long)s0 * ws->incr + ws->next;
+ e = (long)e0 * ws->incr + ws->next;
+
+ *pstart = s;
+ *pend = e;
+
+ if (e0 == n)
+ thr->ts.static_trip = -1;
+ else
+ thr->ts.static_trip++;
+ return 0;
+ }
+}
+
+
+/* This function implements the DYNAMIC scheduling method. Arguments are
+ as for gomp_iter_static_next. This function must be called with ws->lock
+ held. */
+
+bool
+gomp_iter_dynamic_next_locked (long *pstart, long *pend)
+{
+ struct gomp_thread *thr = gomp_thread ();
+ struct gomp_work_share *ws = thr->ts.work_share;
+ long start, end, chunk, left;
+
+ start = ws->next;
+ if (start == ws->end)
+ return false;
+
+ chunk = ws->chunk_size * ws->incr;
+ left = ws->end - start;
+ if (ws->incr < 0)
+ {
+ if (chunk < left)
+ chunk = left;
+ }
+ else
+ {
+ if (chunk > left)
+ chunk = left;
+ }
+ end = start + chunk;
+
+ ws->next = end;
+ *pstart = start;
+ *pend = end;
+ return true;
+}
+
+
+#ifdef HAVE_SYNC_BUILTINS
+/* Similar, but doesn't require the lock held, and uses compare-and-swap
+ instead. Note that the only memory value that changes is ws->next. */
+
+bool
+gomp_iter_dynamic_next (long *pstart, long *pend)
+{
+ struct gomp_thread *thr = gomp_thread ();
+ struct gomp_work_share *ws = thr->ts.work_share;
+ long start, end, nend, chunk, incr;
+
+ start = ws->next;
+ end = ws->end;
+ incr = ws->incr;
+ chunk = ws->chunk_size * incr;
+
+ while (1)
+ {
+ long left = end - start;
+ long tmp;
+
+ if (start == end)
+ return false;
+
+ if (incr < 0)
+ {
+ if (chunk < left)
+ chunk = left;
+ }
+ else
+ {
+ if (chunk > left)
+ chunk = left;
+ }
+ nend = start + chunk;
+
+ tmp = __sync_val_compare_and_swap (&ws->next, start, nend);
+ if (__builtin_expect (tmp == start, 1))
+ break;
+
+ start = tmp;
+ }
+
+ *pstart = start;
+ *pend = nend;
+ return true;
+}
+#endif /* HAVE_SYNC_BUILTINS */
+
+
+/* This function implements the GUIDED scheduling method. Arguments are
+ as for gomp_iter_static_next. This function must be called with the
+ work share lock held. */
+
+bool
+gomp_iter_guided_next_locked (long *pstart, long *pend)
+{
+ struct gomp_thread *thr = gomp_thread ();
+ struct gomp_work_share *ws = thr->ts.work_share;
+ struct gomp_team *team = thr->ts.team;
+ unsigned long nthreads = team ? team->nthreads : 1;
+ unsigned long n, q;
+ long start, end;
+
+ if (ws->next == ws->end)
+ return false;
+
+ n = (ws->end - ws->next) / ws->incr;
+ q = (n + nthreads - 1) / nthreads;
+
+ if (q < ws->chunk_size)
+ q = ws->chunk_size;
+ if (q > n)
+ q = n;
+
+ start = ws->next;
+ end = start + q * ws->incr;
+
+ ws->next = end;
+ *pstart = start;
+ *pend = end;
+ return true;
+}
+
+#ifdef HAVE_SYNC_BUILTINS
+/* Similar, but doesn't require the lock held, and uses compare-and-swap
+ instead. Note that the only memory value that changes is ws->next. */
+
+bool
+gomp_iter_guided_next (long *pstart, long *pend)
+{
+ struct gomp_thread *thr = gomp_thread ();
+ struct gomp_work_share *ws = thr->ts.work_share;
+ struct gomp_team *team = thr->ts.team;
+ unsigned long nthreads = team ? team->nthreads : 1;
+ long start, end, nend, incr;
+ unsigned long chunk_size;
+
+ start = ws->next;
+ end = ws->end;
+ incr = ws->incr;
+ chunk_size = ws->chunk_size;
+
+ while (1)
+ {
+ unsigned long n, q;
+ long tmp;
+
+ if (start == end)
+ return false;
+
+ n = (end - start) / ws->incr;
+ q = (n + nthreads - 1) / nthreads;
+
+ if (q < chunk_size)
+ q = chunk_size;
+ if (q > n)
+ q = n;
+
+ nend = start + q * incr;
+
+ tmp = __sync_val_compare_and_swap (&ws->next, start, nend);
+ if (__builtin_expect (tmp == start, 1))
+ break;
+
+ start = tmp;
+ }
+
+ *pstart = start;
+ *pend = nend;
+ return true;
+}
+#endif /* HAVE_SYNC_BUILTINS */
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