MPI Point-to-Point Communication Modes

Send Modes	MPI function	Completion Condition
Synchronous send	MPI_Ssend	only completes when the receive has completed
Buffered send	MPI_Bsend	always completes (unless an error occurs) irrespective of the receiver
**Standard send	MPI_Send	message sent (receive state unknown)
Ready send	MPI_Rsend	may be used only when the a matching receive has already been posted

Receive Mode	MPI function	Completion Condition
Receive	MPI_Recv	Complete when a message has arrived

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Blocking and Non-blocking Communication

• blocking send or receive
• call does not return until the operation has been completed
• allows you to know when it is safe to use the data received or reuse the data sent
• non-blocking send or receive
• call returns immediately without knowing if the operation has been completed
• allows you to overlap other computation while testing for the operation to be completed
• less possibility of deadlocking code
• used with MPI_Wait or MPI_Test
  

Type of Commmunication	MPI Function
blocking send	MPI_Send
non-blocking send	MPI_Isend
blocking receive	MPI_Recv
non-blocking receive	MPI_Irecv