libgomp/doc/openacc-library-and-environment-variables.rst

   1 ..
   2   Copyright 1988-2022 Free Software Foundation, Inc.
   3   This is part of the GCC manual.
   4   For copying conditions, see the copyright.rst file.
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   6 OpenACC library and environment variables
   7 *****************************************
   8
   9 There are two environment variables associated with the OpenACC library
  10 that may be used to control the device type and device number:
  11 :envvar:`ACC_DEVICE_TYPE` and :envvar:`ACC_DEVICE_NUM`, respectively. These two
  12 environment variables can be used as an alternative to calling
  13 ``acc_set_device_num()``. As seen in the second use case, the device
  14 type and device number were specified using ``acc_set_device_num()``.
  15 If however, the aforementioned environment variables were set, then the
  16 call to ``acc_set_device_num()`` would not be required.
  17
  18 The use of the environment variables is only relevant when an OpenACC function
  19 is called prior to a call to ``cudaCreate()``. If ``cudaCreate()``
  20 is called prior to a call to an OpenACC function, then you must call
  21 ``acc_set_device_num()`` [#f1]_.
  22
  23 .. -
  24    OpenACC Profiling Interface
  25    -
  26
  27 .. [#f1] More complete information
  28   about :envvar:`ACC_DEVICE_TYPE` and :envvar:`ACC_DEVICE_NUM` can be found in
  29   sections 4.1 and 4.2 of the `OpenACC <https://www.openacc.org>`_
  30   Application Programming Interface”, Version 2.6.