anchor.diff:      (values (not (zerop (mem-ref flag* :int))) request)))
   
   (defun mpi-wait (request)
  +  "Blocks until REQUEST has been completed."
     (declare (type mpi-request request))
     (with-foreign-objects ((status* '(:struct mpi-status))
                            (request* 'mpi-request))
  
positive.code:     request))
  
  (defun mpi-waitall (&rest requests)
    (let ((n-requests (length requests)))
      (with-foreign-objects ((requests* 'mpi-request n-requests)
                             (statuses* '(:struct mpi-status) n-requests))
  
negative.code:          mpi-tag)))))
  
  (defun mpi-test (request)
    "Returns whether REQUEST has been completed.
  
  MPI makes a progress guarantee, such that repeated calls to MPI-TEST to a
  request whose matching operation has been issued will eventually succeed."
    (declare (type mpi-request request))
    (with-foreign-objects ((status* '(:struct mpi-status))
                           (flag* :int)
  