Send Modes

blocking

does not return until the message data and envelope have been safely stored away so that the sender is free to access and overwrite the send buffer

standard

$\,$

• unspecified as to buffering
• can be started regardless of the state of the receiver
• unspecified as to locality: it may or may not complete depending on or regardless of the state of the receiver
• MPI_Send

buffered

$\,$

• can be started regardless of the state of the receiver
• is local, i.e., its completion is independent of the state of the receiver
• MPI_Bsend

synchronous

$\,$

• can be started whether or not a matching receive was posted
• is non-local: completes only if a matching receive is posted
• MPI_Ssend

ready

$\,$

• can be started only when the matching receive has been posted - otherwise an error is returned.
• completes regardless of whether the message has been fully received.
• MPI_Rsend