1  /* Detect the number of processors.
       2  
       3     Copyright (C) 2009-2023 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++ */