In SMPI, this depends on the message size, that is compared against two thresholds:
- if (size < :ref:`smpi/async-small-thresh <cfg=smpi/async-small-thresh>`) then
- MPI_Send returns immediately, even if the corresponding receive has not be issued yet.
-- if (:ref:`smpi/async-small-thresh <cfg=smpi/async-small-thresh>` < size < :ref:`smpi/send-is-detached-thresh <cfg=smpi/send-is-detached-thresh>`) then
- MPI_Send returns as soon as the corresponding receive has been issued. This is known as the eager mode.
+ MPI_Send returns immediately, and the message is sent even if the
+ corresponding receive has not be issued yet.
+- if (:ref:`smpi/async-small-thresh <cfg=smpi/async-small-thresh>` < size <
+ :ref:`smpi/send-is-detached-thresh <cfg=smpi/send-is-detached-thresh>`) then
+ MPI_Send also returns immediately, but SMPI waits for the corresponding
+ receive to be posted, in order to perform the communication operation. This is
+ known as the eager mode.
- if (:ref:`smpi/send-is-detached-thresh <cfg=smpi/send-is-detached-thresh>` < size) then
MPI_Send returns only when the message has actually been sent over the network. This is known as the rendez-vous mode.
