lib/nproc.h

   1 /* Detect the number of processors.
   2
   3    Copyright (C) 2009-2024 Free Software Foundation, Inc.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    This file 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 Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Glen Lenker and Bruno Haible.  */
  19
  20 /* Allow the use in C++ code.  */
  21 #ifdef __cplusplus
  22 extern "C" {
  23 #endif
  24
  25 /* A "processor" in this context means a thread execution unit, that is either
  26    - an execution core in a (possibly multi-core) chip, in a (possibly multi-
  27      chip) module, in a single computer, or
  28    - a thread execution unit inside a core
  29      (hyper-threading, see <https://en.wikipedia.org/wiki/Hyper-threading>).
  30    Which of the two definitions is used, is unspecified.  */
  31
  32 enum nproc_query
  33 {
  34   NPROC_ALL,                 /* total number of processors */
  35   NPROC_CURRENT,             /* processors available to the current process */
  36   NPROC_CURRENT_OVERRIDABLE  /* likewise, but overridable through the
  37                                 OMP_NUM_THREADS environment variable */
  38 };
  39
  40 /* Return the total number of processors.  The result is guaranteed to
  41    be at least 1.  */
  42 extern unsigned long int num_processors (enum nproc_query query);
  43
  44 #ifdef __cplusplus
  45 }
  46 #endif /* C++ */