mirror of
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96 lines
3 KiB
C
96 lines
3 KiB
C
/*
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* Copyright (c) 2003, 2007-14 Matteo Frigo
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* Copyright (c) 2003, 2007-14 Massachusetts Institute of Technology
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*
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*/
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/* openmp.c: thread spawning via OpenMP */
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#include "threads/threads.h"
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#if !defined(_OPENMP)
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#error OpenMP enabled but not using an OpenMP compiler
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#endif
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int X(ithreads_init)(void)
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{
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return 0; /* no error */
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}
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/* Distribute a loop from 0 to loopmax-1 over nthreads threads.
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proc(d) is called to execute a block of iterations from d->min
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to d->max-1. d->thr_num indicate the number of the thread
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that is executing proc (from 0 to nthreads-1), and d->data is
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the same as the data parameter passed to X(spawn_loop).
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This function returns only after all the threads have completed. */
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void X(spawn_loop)(int loopmax, int nthr, spawn_function proc, void *data)
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{
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int block_size;
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spawn_data d;
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int i;
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A(loopmax >= 0);
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A(nthr > 0);
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A(proc);
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if (!loopmax) return;
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/* Choose the block size and number of threads in order to (1)
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minimize the critical path and (2) use the fewest threads that
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achieve the same critical path (to minimize overhead).
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e.g. if loopmax is 5 and nthr is 4, we should use only 3
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threads with block sizes of 2, 2, and 1. */
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block_size = (loopmax + nthr - 1) / nthr;
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nthr = (loopmax + block_size - 1) / block_size;
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if (X(spawnloop_callback)) { /* user-defined spawnloop backend */
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spawn_data *sdata;
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STACK_MALLOC(spawn_data *, sdata, sizeof(spawn_data) * nthr);
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for (i = 0; i < nthr; ++i) {
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spawn_data *d = &sdata[i];
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d->max = (d->min = i * block_size) + block_size;
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if (d->max > loopmax)
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d->max = loopmax;
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d->thr_num = i;
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d->data = data;
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}
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X(spawnloop_callback)(proc, sdata, sizeof(spawn_data), nthr, X(spawnloop_callback_data));
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STACK_FREE(sdata);
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return;
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}
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#pragma omp parallel for private(d)
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for (i = 0; i < nthr; ++i) {
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d.max = (d.min = i * block_size) + block_size;
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if (d.max > loopmax)
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d.max = loopmax;
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d.thr_num = i;
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d.data = data;
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proc(&d);
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}
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}
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void X(threads_cleanup)(void)
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{
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}
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/* FIXME [Matteo Frigo 2015-05-25] What does "thread-safe"
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mean for openmp? */
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void X(threads_register_planner_hooks)(void)
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{
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}
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