nd these will be discussed in the next section.

   Once the call to 'acc_set_device_num()' has completed, other OpenACC
functions can be called as seen with multiple calls being made to
'acc_copyin()'.  In addition, calls can be made to functions in the
CUBLAS library.  In the use case a call to 'cublasCreate()' is made
subsequent to the calls to 'acc_copyin()'.  As seen in the previous use
case, a call to 'cublasCreate()' initializes the CUBLAS library and
allocates the hardware resources on the host and the device.  However,
since the device has already been allocated, 'cublasCreate()' will only
initialize the CUBLAS library and allocate the appropriate hardware
resources on the host.  The context that was created as part of the
OpenACC initialization is shared with the CUBLAS library, similarly to
the first use case.

         dev = 0;

         acc_set_device_num(dev, acc_device_nvidia);

         /* Copy the first set to the device */
         d_X = acc_copyin(&h_X[0], N * sizeof (float));
         if (d_X == NULL)
         {
             fprintf(stderr, "copyin error h_X\n");
             exit(EXIT_FAILURE);
         }

         /* Copy the second set to the device */
         d_Y = acc_copyin(&h_Y1[0], N * sizeof (float));
         if (d_Y == NULL)
         {
             fprintf(stderr, "copyin error h_Y1\n");
             exit(EXIT_FAILURE);
         }

         /* Create the handle */
         s = cublasCreate(&h);
         if (s != CUBLAS_STATUS_SUCCESS)
         {
             fprintf(stderr, "cublasCreate failed %d\n", s);
             exit(EXIT_FAILURE);
         }

         /* Perform saxpy using CUBLAS library function */
         s = cublasSaxpy(h, N, &alpha, d_X, 1, d_Y, 1);
         if (s != CUBLAS_STATUS_SUCCESS)
         {
             fprintf(stderr, "cublasSaxpy failed %d\n", s);
             exit(EXIT_FAILURE);
         }

         /* Copy the results from the device */
         acc_memcpy_from_device(&h_Y1[0], d_Y, N * sizeof (float));

                              Use Case 2

8.4 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:
'ACC_DEVICE_TYPE' and '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()'(2)

   ---------- Footnotes ----------

   (1) See section 2.26, "Interactions with the CUDA Driver API" in
"CUDA Runtime API", Version 5.5, and section 2.27, "VDPAU
Interoperability", in "CUDA Driver API", TRM-06703-001, Version 5.5, for
additional information on library interoperability.

   (2) More complete information about 'ACC_DEVICE_TYPE' and
'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.