acc_async_test– Test for completion of a specific asynchronous operation.
This function tests for completion of the asynchrounous operation specified
in arg. In C/C++, a non-zero value will be returned to indicate
the specified asynchronous operation has completed. While Fortran will return
true. If the asynchrounous operation has not completed, C/C++ returns
a zero and Fortran returns a
OpenACC specification v2.0, section 3.2.6.