1 /*
2 * Copyright (c) 2003, 2007-14 Matteo Frigo
3 * Copyright (c) 2003, 2007-14 Massachusetts Institute of Technology
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
18 *
19 */
20
21 /* openmp.c: thread spawning via OpenMP */
22
23 #include "threads/threads.h"
24
25 #if !defined(_OPENMP)
26 #error OpenMP enabled but not using an OpenMP compiler
27 #endif
28
X(ithreads_init)29 int X(ithreads_init)(void)
30 {
31 return 0; /* no error */
32 }
33
34 /* Distribute a loop from 0 to loopmax-1 over nthreads threads.
35 proc(d) is called to execute a block of iterations from d->min
36 to d->max-1. d->thr_num indicate the number of the thread
37 that is executing proc (from 0 to nthreads-1), and d->data is
38 the same as the data parameter passed to X(spawn_loop).
39
40 This function returns only after all the threads have completed. */
X(spawn_loop)41 void X(spawn_loop)(int loopmax, int nthr, spawn_function proc, void *data)
42 {
43 int block_size;
44 spawn_data d;
45 int i;
46
47 A(loopmax >= 0);
48 A(nthr > 0);
49 A(proc);
50
51 if (!loopmax) return;
52
53 /* Choose the block size and number of threads in order to (1)
54 minimize the critical path and (2) use the fewest threads that
55 achieve the same critical path (to minimize overhead).
56 e.g. if loopmax is 5 and nthr is 4, we should use only 3
57 threads with block sizes of 2, 2, and 1. */
58 block_size = (loopmax + nthr - 1) / nthr;
59 nthr = (loopmax + block_size - 1) / block_size;
60
61 if (X(spawnloop_callback)) { /* user-defined spawnloop backend */
62 spawn_data *sdata;
63 STACK_MALLOC(spawn_data *, sdata, sizeof(spawn_data) * nthr);
64 for (i = 0; i < nthr; ++i) {
65 spawn_data *d = &sdata[i];
66 d->max = (d->min = i * block_size) + block_size;
67 if (d->max > loopmax)
68 d->max = loopmax;
69 d->thr_num = i;
70 d->data = data;
71 }
72 X(spawnloop_callback)(proc, sdata, sizeof(spawn_data), nthr, X(spawnloop_callback_data));
73 STACK_FREE(sdata);
74 return;
75 }
76
77 #pragma omp parallel for private(d)
78 for (i = 0; i < nthr; ++i) {
79 d.max = (d.min = i * block_size) + block_size;
80 if (d.max > loopmax)
81 d.max = loopmax;
82 d.thr_num = i;
83 d.data = data;
84 proc(&d);
85 }
86 }
87
X(threads_cleanup)88 void X(threads_cleanup)(void)
89 {
90 }
91
92 /* FIXME [Matteo Frigo 2015-05-25] What does "thread-safe"
93 mean for openmp? */
X(threads_register_planner_hooks)94 void X(threads_register_planner_hooks)(void)
95 {
96 }
97