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/* Copyright (C) 2007-2022 Free Software Foundation, Inc.
Contributed by Danny Smith <>
This file is part of the GNU Offloading and Multi Processing Library
Libgomp is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, 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 General Public License for
more details.
Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.
You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<>. */
/* This file contains system specific routines related to counting
online processors and dynamic load balancing. It is expected that
a system may well want to write special versions of each of these.
The following implementation uses win32 API routines. */
#include "libgomp.h"
#include <windows.h>
/* Count the CPU's currently available to this process. */
static unsigned int
count_avail_process_cpus ()
DWORD_PTR process_cpus;
DWORD_PTR system_cpus;
if (GetProcessAffinityMask (GetCurrentProcess (),
&process_cpus, &system_cpus))
unsigned int count;
for (count = 0; process_cpus != 0; process_cpus >>= 1)
if (process_cpus & 1)
return count;
return 1;
/* At startup, determine the default number of threads. It would seem
this should be related to the number of cpus available to the process. */
gomp_init_num_threads (void)
gomp_global_icv.nthreads_var = count_avail_process_cpus ();
/* When OMP_DYNAMIC is set, at thread launch determine the number of
threads we should spawn for this team. FIXME: How do we adjust for
load average on MS Windows? */
gomp_dynamic_max_threads (void)
unsigned int n_onln = count_avail_process_cpus ();
unsigned int nthreads_var = gomp_icv (false)->nthreads_var;
return n_onln > nthreads_var ? nthreads_var : n_onln;
omp_get_num_procs (void)
return count_avail_process_cpus ();
ialias (omp_get_num_procs)