[thirdparty/gcc.git] / libgomp / doc / openacc-library-and-environment-variables.rst

..
  Copyright 1988-2022 Free Software Foundation, Inc.
  This is part of the GCC manual.
  For copying conditions, see the copyright.rst file.

OpenACC library and environment variables
*****************************************

There are two environment variables associated with the OpenACC library
that may be used to control the device type and device number:
:envvar:`ACC_DEVICE_TYPE` and :envvar:`ACC_DEVICE_NUM`, respectively. These two
environment variables can be used as an alternative to calling
``acc_set_device_num()``. As seen in the second use case, the device
type and device number were specified using ``acc_set_device_num()``.
If however, the aforementioned environment variables were set, then the
call to ``acc_set_device_num()`` would not be required.

The use of the environment variables is only relevant when an OpenACC function
is called prior to a call to ``cudaCreate()``. If ``cudaCreate()``
is called prior to a call to an OpenACC function, then you must call
``acc_set_device_num()`` [#f1]_.

.. -
   OpenACC Profiling Interface
   -

.. [#f1] More complete information
  about :envvar:`ACC_DEVICE_TYPE` and :envvar:`ACC_DEVICE_NUM` can be found in
  sections 4.1 and 4.2 of the `OpenACC <https://www.openacc.org>`_
  Application Programming Interface”, Version 2.6.
Commit	Line	Data
c63539ff ML	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.
	5
	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>`_
3ed1b4ce	30	Application Programming Interface”, Version 2.6.