MPI_ISENDRECV_REPLACE(3)

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💅 MPI_ISENDRECV_REPLACE — Open MPI, section 3 🎀

okay bestie, sit down, hydrate, and let me tell you about the absolute icon of a function that is MPI_Isendrecv_replace ✨

real talk: it sends and receives a message using a single buffer. one buffer. both jobs. main character energy honestly 👑

🔧 SYNTAX

C Syntax

#include <mpi.h>

int MPI_Isendrecv_replace(void *buf, int count, MPI_Datatype datatype,
    int dest, int sendtag, int source, int recvtag, MPI_Comm comm,
    MPI_Request *request)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_ISENDRECV_REPLACE(BUF, COUNT, DATATYPE, DEST, SENDTAG, SOURCE,
        RECVTAG, COMM, REQUEST, IERROR)
    <type>    BUF(*)
    INTEGER    COUNT, DATATYPE, DEST, SENDTAG
    INTEGER    SOURCE, RECVTAG, COMM
    INTEGER    REQUEST, IERROR

Fortran 2008 Syntax

USE mpi_f08
MPI_Isendrecv_replace(buf, count, datatype, dest, sendtag, source, recvtag,
        comm, request, ierror)
    TYPE(*), DIMENSION(..) :: buf
    INTEGER, INTENT(IN) :: count, dest, sendtag, source, recvtag
    TYPE(MPI_Datatype), INTENT(IN) :: datatype
    TYPE(MPI_Comm), INTENT(IN) :: comm
    TYPE(MPI_Request) :: request
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror

🔁 INPUT/OUTPUT PARAMETER

  • buf — the initial address of the send and receive buffer. yes she does both, it's giving multitasking 💖 (choice)

📥 INPUT PARAMETERS

  • count — number of elements in the send and receive buffer (integer)
  • datatype — type of elements to send and receive (handle)
  • dest — rank of destination (integer)
  • sendtag — send message tag (integer)
  • source — rank of source (integer)
  • recvtag — receive message tag (integer)
  • comm — communicator (handle)

📤 OUTPUT PARAMETERS

  • request — communication request (handle)
  • ierror — Fortran only: error status (integer)

🌈 DESCRIPTION

so the non-blocking send-receive operations combine in one call the sending of a message to one destination and the receiving of another message, from another process. one call. two jobs. slay 🫶

the two (source and destination) are possibly the same, so don't freak out if you see yourself in the mirror there.

a send-receive operation is useful for executing a shift operation across a chain of processes 💫 And bestie, it can be used in conjunction with the functions described in the “Process Topologies” chapter of the MPI Standard in order to perform shifts on various logical topologies. also, a send-receive operation is useful for implementing remote procedure calls. iykyk.

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. it's mutual, it's open, it's a healthy relationship 💜

MPI_Isendrecv_replace executes a non-blocking send and receive. The same buffer is used both for the send and for the receive, so that the message sent is replaced by the message received. yes bestie, same buffer, out with the old, in with the new 🦋

and how do you know when it's done? a non-blocking send-receive request can be determined to be completed by calling the MPI_Wait, MPI_Waitany, MPI_Test, or MPI_Testany with the request returned by this function. periodt. 💅

💀 ERRORS

ngl the error section is long but it's important, so we're reading all of it. no skipping 🍓

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. like, no promises bestie, this is real 💀

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.

See also:

  • MPI_Isendrecv
  • MPI_Sendrecv
  • MPI_Sendrecv_replace
2003-2026, The Open MPI Community

and that's the whole page, bestie 🥰 you ate. go forth and shift those processes across your chain, you iconic little communicator 👑

© 2003-2026, The Open MPI Community — and this cutie was written down on Sep 10, 2026, stamped into section 3 of the Open MPI manual 🌸 mwah, see u next manpage 💖

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