MPI_SENDRECV(3)

💌 MPI_Sendrecv — sends and receives a message 💌

okay bestie, welcome to the Open MPI manual page for MPI_Sendrecv — the one-call send-and-receive combo that's basically the group-chat "u up?" of point-to-point communication. ✨ It sends a message and receives a message in one move, and yes, every detail below is staying exactly where it belongs. 🫶

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✨ SYNTAX ✨

🧸 C Syntax

          #include <mpi.h>

          int MPI_Sendrecv(const void *sendbuf, int sendcount, MPI_Datatype sendtype,
               int dest, int sendtag, void *recvbuf, int recvcount,
               MPI_Datatype recvtype, int source, int recvtag,
               MPI_Comm comm, MPI_Status *status)

🧵 Fortran Syntax

          USE MPI
          ! or the older form: INCLUDE 'mpif.h'
          MPI_SENDRECV(SENDBUF, SENDCOUNT, SENDTYPE, DEST, SENDTAG,
                       RECVBUF, RECVCOUNT, RECVTYPE, SOURCE, RECVTAG, COMM,
                       STATUS, IERROR)
               <type>  SENDBUF(*), RECVBUF(*)
               INTEGER SENDCOUNT, SENDTYPE, DEST, SENDTAG
               INTEGER RECVCOUNT, RECVTYPE, SOURCE, RECVTAG, COMM
               INTEGER STATUS(MPI_STATUS_SIZE), IERROR

🦋 Fortran 2008 Syntax

          USE mpi_f08
          MPI_Sendrecv(sendbuf, sendcount, sendtype, dest, sendtag, recvbuf,
                       recvcount, recvtype, source, recvtag, comm, status, ierror)
               TYPE(*), DIMENSION(..), INTENT(IN) :: sendbuf
               TYPE(*), DIMENSION(..) :: recvbuf
               INTEGER, INTENT(IN) :: sendcount, dest, sendtag, recvcount, source,
               recvtag
               TYPE(MPI_Datatype), INTENT(IN) :: sendtype, recvtype
               TYPE(MPI_Comm), INTENT(IN) :: comm
               TYPE(MPI_Status) :: status
               INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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🎀 INPUT PARAMETERS 🎀

• sendbuf — initial address of send buffer (choice). This is where the stuff you're sending starts. 💅
• sendcount — number of elements to send (integer).
• sendtype — type of elements in send buffer (handle).
• dest — rank of destination (integer).
• sendtag — send tag (integer).
• recvcount — maximum number of elements to receive (integer).
• recvtype — type of elements in receive buffer (handle).
• source — rank of source (integer).
• recvtag — receive tag (integer).
• comm — communicator (handle).

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💖 OUTPUT PARAMETERS 💖

• recvbuf — initial address of receive buffer (choice).
• status — status object (status). This refers to the receive operation.
• ierror — Fortran only: Error status (integer).

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🌸 DESCRIPTION 🌸

okay so here's the vibe: a send-receive operation smooshes two things into one call — it sends a message to one destination and receives another message from another process. The two ranks (source and destination) are possibly the same, so don't assume they have to be different. 💅

This is a whole mood for executing a shift operation across a chain of processes. If you use blocking sends and receives for that kind of shift, you have to order them correctly (for example: even processes send, then receive; odd processes receive first, then send) so you don't create cyclic dependencies that may lead to deadlock. 💀 When a send-receive operation is used, the communication subsystem takes care of these issues for you. You can also pair it with the functions described in the “Process Topologies” chapter in the MPI Standard to perform shifts on various logical topologies. And it's useful for implementing remote procedure calls, too. ✨

A message sent by a send-receive operation can be received by a regular receive operation or probed by a probe operation; a send-receive operation can receive a message sent by a regular send operation. 👀

MPI_Sendrecv executes a blocking send and receive operation. Both send and receive use the same communicator, but possibly different tags. The send buffer and receive buffers must be disjoint — no overlap, bestie — and may have different lengths and datatypes. 🎀

If your application does not need to examine the status field, you can save resources by using the predefined constant MPI_STATUS_IGNORE as a special value for the status argument. 🫶

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🚨 ERRORS 🚨

Almost all MPI routines return an error value; C routines as the return result of the function and Fortran routines in the last argument.

Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before MPI_Init/MPI_Init_thread, after MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/MPI_Comm_spawn_multiple. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions. 🚨

Open MPI includes three predefined error handlers that can be used:

• MPI_ERRORS_ARE_FATAL — causes the program to abort all connected MPI processes. 💀
• MPI_ERRORS_ABORT — an error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if MPI_Abort was called on that communicator. If called on a window or file, acts as if MPI_Abort was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process.
• MPI_ERRORS_RETURN — returns an error code to the application.

MPI applications can also implement their own error handlers by calling:

• MPI_Comm_create_errhandler then MPI_Comm_set_errhandler
• MPI_File_create_errhandler then MPI_File_set_errhandler
• MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init
• MPI_Win_create_errhandler then MPI_Win_set_errhandler

Note that MPI does not guarantee that an MPI program can continue past an error. 😭

See the MPI man page for a full list of MPI error codes.

See the Error Handling section of the MPI-3.1 standard for more information.

Note that per the “Return Status” section in the “Point-to-Point Communication” chapter in the MPI Standard, MPI errors on messages received by MPI_Sendrecv do not set the status.MPI_ERROR field in the returned status. The error code is always passed to the back-end error handler and may be passed back to the caller through the return value of MPI_Sendrecv if the back-end error handler returns it. The pre-defined MPI error handler MPI_ERRORS_RETURN exhibits this behavior, for example. 👀

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👀 SEE ALSO 👀

• MPI_Sendrecv_replace

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📜 COPYRIGHT 📜

2003-2026, The Open MPI Community

and that's the whole page, bestie — Open MPI's MPI_Sendrecv(3), dated Sep 11, 2026. mwah 💖