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() 1.