libgomp/doc/openacc-runtime-library-routines/accpresentorcreate.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.
   5
   6 .. _acc_present_or_create:
   7
   8 acc_present_or_create -- If the data is not present on the device, allocate device memory and map it to host memory.
   9 ********************************************************************************************************************
  10
  11 Description
  12   This function tests if the host data specified by :samp:`{a}` and of length
  13   :samp:`{len}` is present or not. If it is not present, then device memory
  14   will be allocated and mapped to host memory. In C/C++, the device address
  15   of the newly allocated device memory is returned.
  16
  17   In Fortran, two (2) forms are supported. In the first form, :samp:`{a}` specifies
  18   a contiguous array section. The second form :samp:`{a}` specifies a variable or
  19   array element and :samp:`{len}` specifies the length in bytes.
  20
  21   Note that ``acc_present_or_create`` and ``acc_pcreate`` exist for
  22   backward compatibility with OpenACC 2.0; use :ref:`acc_create` instead.
  23
  24 C/C++:
  25   .. list-table::
  26
  27      * - *Prototype*:
  28        - ``void *acc_present_or_create(h_void *a, size_t len)``
  29      * - *Prototype*:
  30        - ``void *acc_pcreate(h_void *a, size_t len)``
  31
  32 Fortran:
  33   .. list-table::
  34
  35      * - *Interface*:
  36        - ``subroutine acc_present_or_create(a)``
  37      * -
  38        - ``type, dimension(:[,:]...) :: a``
  39      * - *Interface*:
  40        - ``subroutine acc_present_or_create(a, len)``
  41      * -
  42        - ``type, dimension(:[,:]...) :: a``
  43      * -
  44        - ``integer len``
  45      * - *Interface*:
  46        - ``subroutine acc_pcreate(a)``
  47      * -
  48        - ``type, dimension(:[,:]...) :: a``
  49      * - *Interface*:
  50        - ``subroutine acc_pcreate(a, len)``
  51      * -
  52        - ``type, dimension(:[,:]...) :: a``
  53      * -
  54        - ``integer len``
  55
  56 Reference:
  57   :openacc:`2.6`, section
  58   3.2.21.