lib/omp-init.c

   1 /* Initialize OpenMP.
   2
   3    Copyright (C) 2017-2021 Free Software Foundation, Inc.
   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, or (at your option)
   8    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, see <https://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 #ifdef _OPENMP
  21
  22 /* Specification.  */
  23 # include <omp.h>
  24
  25 #endif
  26
  27 #include <stdlib.h>
  28
  29 #include "c-ctype.h"
  30
  31 #if defined _AIX
  32
  33 /* Parse OMP environment variables without dependence on OMP.
  34    Return 0 for invalid values.  */
  35 static unsigned long int
  36 parse_omp_threads (char const* threads)
  37 {
  38   unsigned long int ret = 0;
  39
  40   if (threads == NULL)
  41     return ret;
  42
  43   /* The OpenMP spec says that the value assigned to the environment variables
  44      "may have leading and trailing white space".  */
  45   while (*threads != '\0' && c_isspace (*threads))
  46     threads++;
  47
  48   /* Convert it from positive decimal to 'unsigned long'.  */
  49   if (c_isdigit (*threads))
  50     {
  51       char *endptr = NULL;
  52       unsigned long int value = strtoul (threads, &endptr, 10);
  53
  54       if (endptr != NULL)
  55         {
  56           while (*endptr != '\0' && c_isspace (*endptr))
  57             endptr++;
  58           if (*endptr == '\0')
  59             return value;
  60           /* Also accept the first value in a nesting level,
  61              since we can't determine the nesting level from env vars.  */
  62           else if (*endptr == ',')
  63             return value;
  64         }
  65     }
  66
  67   return ret;
  68 }
  69
  70 #endif
  71
  72 void
  73 openmp_init (void)
  74 {
  75   /* On AIX 7.2, in 32-bit mode, use of OpenMP on machines with 64 or 128
  76      processors makes the program fail with an error message
  77      "1587-120 SMP runtime library error. Memory allocation failed when creating thread number 62.".
  78      The workaround is to tell the OpenMP library to create fewer than 62
  79      threads.  This can be done through the OMP_THREAD_LIMIT environment
  80      variable.  */
  81 #if defined _AIX
  82   if (sizeof (long) == sizeof (int))
  83     {
  84       /* Ensure that OMP_THREAD_LIMIT has a value <= 32.  */
  85       unsigned long int omp_env_limit =
  86         parse_omp_threads (getenv ("OMP_THREAD_LIMIT"));
  87
  88       if (!(omp_env_limit > 0 && omp_env_limit <= 32))
  89         setenv ("OMP_THREAD_LIMIT", "32", 1);
  90     }
  91 #endif
  92 }