MPIRecv

MPI_Recv is a blocking point-to-point receive operation in the Message Passing Interface (MPI). It receives a message that matches the specified source, tag, and communicator and stores the data in a user-provided buffer. The call blocks until a matching message is available or an error occurs.

Signature

int MPI_Recv(void *buf, int count, MPI_Datatype datatype, int source, int tag, MPI_Comm comm, MPI_Status *status);

Parameters

- buf: pointer to the receive buffer where data will be stored.

- count: number of elements of datatype to receive.

- datatype: MPI datatype describing the data in buf.

- source: rank of the sending process or MPI_ANY_SOURCE to accept from any source.

- tag: message tag or MPI_ANY_TAG to accept any tag.

- comm: communicator containing the communicating processes.

- status: MIDI_Status object that returns information about the received message (source, tag, and count). Use MPI_STATUS_IGNORE to skip retrieving status.

Behavior and semantics

MPI_Recv blocks until a message that matches the specified source, tag, and communicator arrives. The received data is placed into the provided buffer. Information about the actual source and tag can be obtained from status if MPI_ANY_SOURCE or MPI_ANY_TAG were used, typically via status.MPI_SOURCE and status.MPI_TAG; the number of received elements can be retrieved with MPI_Get_count. The receive must have a buffer large enough to hold the incoming message; otherwise an error may occur. The operation participates in the standard MPI message matching rules, which include buffering and queueing according to communicator, source, and tag.

Related topics

Non-blocking variant: MPI_Irecv, which posts a non-blocking receive and completes later via MPI_Wait or MPI_Test. MPI_Recv is the counterpart that completes only after a message has been received.