Non-blocking Routines
•Non-blocking routines return immediately .
•They do not wait for the actual arrival of the message nor for the sending protocols to be finished.
•The MPI library performs these tasks whenever it is able to with the user having no control.
•These routines are intrinsically unsafe as there is the danger that the application buffers may be modified by the program without ascertaining whether the non-blocking operation has been completed or not.
•Non-blocking routines allow communications and computations to overlap .