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748086b7 | 1 | /* Copyright (C) 2005, 2008, 2009 Free Software Foundation, Inc. |
a68ab351 JJ |
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 | |
748086b7 JJ |
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. | |
a68ab351 JJ |
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 | |
748086b7 | 13 | FOR A PARTICULAR PURPOSE. See the GNU General Public License for |
a68ab351 JJ |
14 | more details. |
15 | ||
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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/>. */ | |
a68ab351 JJ |
24 | |
25 | /* This file contains routines for managing work-share iteration, both | |
26 | for loops and sections. */ | |
27 | ||
28 | #include "libgomp.h" | |
29 | #include <stdlib.h> | |
30 | ||
31 | typedef unsigned long long gomp_ull; | |
32 | ||
33 | /* This function implements the STATIC scheduling method. The caller should | |
34 | iterate *pstart <= x < *pend. Return zero if there are more iterations | |
35 | to perform; nonzero if not. Return less than 0 if this thread had | |
36 | received the absolutely last iteration. */ | |
37 | ||
38 | int | |
39 | gomp_iter_ull_static_next (gomp_ull *pstart, gomp_ull *pend) | |
40 | { | |
41 | struct gomp_thread *thr = gomp_thread (); | |
42 | struct gomp_team *team = thr->ts.team; | |
43 | struct gomp_work_share *ws = thr->ts.work_share; | |
44 | unsigned long nthreads = team ? team->nthreads : 1; | |
45 | ||
46 | if (thr->ts.static_trip == -1) | |
47 | return -1; | |
48 | ||
49 | /* Quick test for degenerate teams and orphaned constructs. */ | |
50 | if (nthreads == 1) | |
51 | { | |
52 | *pstart = ws->next_ull; | |
53 | *pend = ws->end_ull; | |
54 | thr->ts.static_trip = -1; | |
55 | return ws->next_ull == ws->end_ull; | |
56 | } | |
57 | ||
58 | /* We interpret chunk_size zero as "unspecified", which means that we | |
59 | should break up the iterations such that each thread makes only one | |
60 | trip through the outer loop. */ | |
61 | if (ws->chunk_size_ull == 0) | |
62 | { | |
63 | gomp_ull n, q, i, s0, e0, s, e; | |
64 | ||
65 | if (thr->ts.static_trip > 0) | |
66 | return 1; | |
67 | ||
68 | /* Compute the total number of iterations. */ | |
69 | if (__builtin_expect (ws->mode, 0) == 0) | |
70 | n = (ws->end_ull - ws->next_ull + ws->incr_ull - 1) / ws->incr_ull; | |
71 | else | |
72 | n = (ws->next_ull - ws->end_ull - ws->incr_ull - 1) / -ws->incr_ull; | |
73 | i = thr->ts.team_id; | |
74 | ||
75 | /* Compute the "zero-based" start and end points. That is, as | |
76 | if the loop began at zero and incremented by one. */ | |
77 | q = n / nthreads; | |
78 | q += (q * nthreads != n); | |
79 | s0 = q * i; | |
80 | e0 = s0 + q; | |
81 | if (e0 > n) | |
82 | e0 = n; | |
83 | ||
84 | /* Notice when no iterations allocated for this thread. */ | |
85 | if (s0 >= e0) | |
86 | { | |
87 | thr->ts.static_trip = 1; | |
88 | return 1; | |
89 | } | |
90 | ||
91 | /* Transform these to the actual start and end numbers. */ | |
92 | s = s0 * ws->incr_ull + ws->next_ull; | |
93 | e = e0 * ws->incr_ull + ws->next_ull; | |
94 | ||
95 | *pstart = s; | |
96 | *pend = e; | |
97 | thr->ts.static_trip = (e0 == n ? -1 : 1); | |
98 | return 0; | |
99 | } | |
100 | else | |
101 | { | |
102 | gomp_ull n, s0, e0, i, c, s, e; | |
103 | ||
104 | /* Otherwise, each thread gets exactly chunk_size iterations | |
105 | (if available) each time through the loop. */ | |
106 | ||
107 | if (__builtin_expect (ws->mode, 0) == 0) | |
108 | n = (ws->end_ull - ws->next_ull + ws->incr_ull - 1) / ws->incr_ull; | |
109 | else | |
110 | n = (ws->next_ull - ws->end_ull - ws->incr_ull - 1) / -ws->incr_ull; | |
111 | i = thr->ts.team_id; | |
112 | c = ws->chunk_size_ull; | |
113 | ||
114 | /* Initial guess is a C sized chunk positioned nthreads iterations | |
115 | in, offset by our thread number. */ | |
116 | s0 = (thr->ts.static_trip * (gomp_ull) nthreads + i) * c; | |
117 | e0 = s0 + c; | |
118 | ||
119 | /* Detect overflow. */ | |
120 | if (s0 >= n) | |
121 | return 1; | |
122 | if (e0 > n) | |
123 | e0 = n; | |
124 | ||
125 | /* Transform these to the actual start and end numbers. */ | |
126 | s = s0 * ws->incr_ull + ws->next_ull; | |
127 | e = e0 * ws->incr_ull + ws->next_ull; | |
128 | ||
129 | *pstart = s; | |
130 | *pend = e; | |
131 | ||
132 | if (e0 == n) | |
133 | thr->ts.static_trip = -1; | |
134 | else | |
135 | thr->ts.static_trip++; | |
136 | return 0; | |
137 | } | |
138 | } | |
139 | ||
140 | ||
141 | /* This function implements the DYNAMIC scheduling method. Arguments are | |
142 | as for gomp_iter_ull_static_next. This function must be called with | |
143 | ws->lock held. */ | |
144 | ||
145 | bool | |
146 | gomp_iter_ull_dynamic_next_locked (gomp_ull *pstart, gomp_ull *pend) | |
147 | { | |
148 | struct gomp_thread *thr = gomp_thread (); | |
149 | struct gomp_work_share *ws = thr->ts.work_share; | |
150 | gomp_ull start, end, chunk, left; | |
151 | ||
152 | start = ws->next_ull; | |
153 | if (start == ws->end_ull) | |
154 | return false; | |
155 | ||
156 | chunk = ws->chunk_size_ull; | |
157 | left = ws->end_ull - start; | |
158 | if (__builtin_expect (ws->mode & 2, 0)) | |
159 | { | |
160 | if (chunk < left) | |
161 | chunk = left; | |
162 | } | |
163 | else | |
164 | { | |
165 | if (chunk > left) | |
166 | chunk = left; | |
167 | } | |
168 | end = start + chunk; | |
169 | ||
170 | ws->next_ull = end; | |
171 | *pstart = start; | |
172 | *pend = end; | |
173 | return true; | |
174 | } | |
175 | ||
176 | ||
177 | #if defined HAVE_SYNC_BUILTINS && defined __LP64__ | |
178 | /* Similar, but doesn't require the lock held, and uses compare-and-swap | |
179 | instead. Note that the only memory value that changes is ws->next_ull. */ | |
180 | ||
181 | bool | |
182 | gomp_iter_ull_dynamic_next (gomp_ull *pstart, gomp_ull *pend) | |
183 | { | |
184 | struct gomp_thread *thr = gomp_thread (); | |
185 | struct gomp_work_share *ws = thr->ts.work_share; | |
186 | gomp_ull start, end, nend, chunk; | |
187 | ||
188 | end = ws->end_ull; | |
189 | chunk = ws->chunk_size_ull; | |
190 | ||
191 | if (__builtin_expect (ws->mode & 1, 1)) | |
192 | { | |
193 | gomp_ull tmp = __sync_fetch_and_add (&ws->next_ull, chunk); | |
194 | if (__builtin_expect (ws->mode & 2, 0) == 0) | |
195 | { | |
196 | if (tmp >= end) | |
197 | return false; | |
198 | nend = tmp + chunk; | |
199 | if (nend > end) | |
200 | nend = end; | |
201 | *pstart = tmp; | |
202 | *pend = nend; | |
203 | return true; | |
204 | } | |
205 | else | |
206 | { | |
207 | if (tmp <= end) | |
208 | return false; | |
209 | nend = tmp + chunk; | |
210 | if (nend < end) | |
211 | nend = end; | |
212 | *pstart = tmp; | |
213 | *pend = nend; | |
214 | return true; | |
215 | } | |
216 | } | |
217 | ||
218 | start = ws->next_ull; | |
219 | while (1) | |
220 | { | |
221 | gomp_ull left = end - start; | |
222 | gomp_ull tmp; | |
223 | ||
224 | if (start == end) | |
225 | return false; | |
226 | ||
227 | if (__builtin_expect (ws->mode & 2, 0)) | |
228 | { | |
229 | if (chunk < left) | |
230 | chunk = left; | |
231 | } | |
232 | else | |
233 | { | |
234 | if (chunk > left) | |
235 | chunk = left; | |
236 | } | |
237 | nend = start + chunk; | |
238 | ||
239 | tmp = __sync_val_compare_and_swap (&ws->next_ull, start, nend); | |
240 | if (__builtin_expect (tmp == start, 1)) | |
241 | break; | |
242 | ||
243 | start = tmp; | |
244 | } | |
245 | ||
246 | *pstart = start; | |
247 | *pend = nend; | |
248 | return true; | |
249 | } | |
250 | #endif /* HAVE_SYNC_BUILTINS */ | |
251 | ||
252 | ||
253 | /* This function implements the GUIDED scheduling method. Arguments are | |
254 | as for gomp_iter_ull_static_next. This function must be called with the | |
255 | work share lock held. */ | |
256 | ||
257 | bool | |
258 | gomp_iter_ull_guided_next_locked (gomp_ull *pstart, gomp_ull *pend) | |
259 | { | |
260 | struct gomp_thread *thr = gomp_thread (); | |
261 | struct gomp_work_share *ws = thr->ts.work_share; | |
262 | struct gomp_team *team = thr->ts.team; | |
263 | gomp_ull nthreads = team ? team->nthreads : 1; | |
264 | gomp_ull n, q; | |
265 | gomp_ull start, end; | |
266 | ||
267 | if (ws->next_ull == ws->end_ull) | |
268 | return false; | |
269 | ||
270 | start = ws->next_ull; | |
271 | if (__builtin_expect (ws->mode, 0) == 0) | |
272 | n = (ws->end_ull - start) / ws->incr_ull; | |
273 | else | |
274 | n = (start - ws->end_ull) / -ws->incr_ull; | |
275 | q = (n + nthreads - 1) / nthreads; | |
276 | ||
277 | if (q < ws->chunk_size_ull) | |
278 | q = ws->chunk_size_ull; | |
279 | if (q <= n) | |
280 | end = start + q * ws->incr_ull; | |
281 | else | |
282 | end = ws->end_ull; | |
283 | ||
284 | ws->next_ull = end; | |
285 | *pstart = start; | |
286 | *pend = end; | |
287 | return true; | |
288 | } | |
289 | ||
290 | #if defined HAVE_SYNC_BUILTINS && defined __LP64__ | |
291 | /* Similar, but doesn't require the lock held, and uses compare-and-swap | |
292 | instead. Note that the only memory value that changes is ws->next_ull. */ | |
293 | ||
294 | bool | |
295 | gomp_iter_ull_guided_next (gomp_ull *pstart, gomp_ull *pend) | |
296 | { | |
297 | struct gomp_thread *thr = gomp_thread (); | |
298 | struct gomp_work_share *ws = thr->ts.work_share; | |
299 | struct gomp_team *team = thr->ts.team; | |
300 | gomp_ull nthreads = team ? team->nthreads : 1; | |
301 | gomp_ull start, end, nend, incr; | |
302 | gomp_ull chunk_size; | |
303 | ||
304 | start = ws->next_ull; | |
305 | end = ws->end_ull; | |
306 | incr = ws->incr_ull; | |
307 | chunk_size = ws->chunk_size_ull; | |
308 | ||
309 | while (1) | |
310 | { | |
311 | gomp_ull n, q; | |
312 | gomp_ull tmp; | |
313 | ||
314 | if (start == end) | |
315 | return false; | |
316 | ||
317 | if (__builtin_expect (ws->mode, 0) == 0) | |
318 | n = (end - start) / incr; | |
319 | else | |
320 | n = (start - end) / -incr; | |
321 | q = (n + nthreads - 1) / nthreads; | |
322 | ||
323 | if (q < chunk_size) | |
324 | q = chunk_size; | |
325 | if (__builtin_expect (q <= n, 1)) | |
326 | nend = start + q * incr; | |
327 | else | |
328 | nend = end; | |
329 | ||
330 | tmp = __sync_val_compare_and_swap (&ws->next_ull, start, nend); | |
331 | if (__builtin_expect (tmp == start, 1)) | |
332 | break; | |
333 | ||
334 | start = tmp; | |
335 | } | |
336 | ||
337 | *pstart = start; | |
338 | *pend = nend; | |
339 | return true; | |
340 | } | |
341 | #endif /* HAVE_SYNC_BUILTINS */ |