Completion routines

Completion Routines

• Two basic ways of checking on nonblocking sends and receives:
  call a wait routine that blocks until completion
  call a test routine that returns a flag to indicate if complete

  Use of nonblocking and completion routines allow computation and communication to be overlapped.

      mpi_wait (request_id, 
                return_status, ierr)
      mpi_test (request_id, flag,
                return_status, ierr)

  mpi_wait blocks until the communication is complete.

  mpi_test returns ``immediately'', and sets flag to true is the communication is complete.