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### 5.18 `acc_present_or_copyin` – If the data is not present on the device, allocate device memory and copy from host memory.

Description

  This function tests if the host data specifed by a and of length len is present or not. If it is not present, then device memory will be allocated and the host memory copied. The device address of the newly allocated device memory is returned.

  In Fortran, two (2) forms are supported. In the first form, a specifies a contiguous array section. The second form a specifies a variable or array element and len specifies the length in bytes.

C/C++:

  Prototype: | `void *acc_present_or_copyin(h_void *a, size_t len);`
  Prototype: | `void *acc_pcopyin(h_void *a, size_t len);`

Fortran:

  Interface: | `subroutine acc_present_or_copyin(a)`
  | `type, dimension(:[,:]...) :: a`
  Interface: | `subroutine acc_present_or_copyin(a, len)`
  | `type, dimension(:[,:]...) :: a`
  | `integer len`
  Interface: | `subroutine acc_pcopyin(a)`
  | `type, dimension(:[,:]...) :: a`
  Interface: | `subroutine acc_pcopyin(a, len)`
  | `type, dimension(:[,:]...) :: a`
  | `integer len`

Reference:

  OpenACC specification v2.0, section 3.2.18.