MPI_ISENDRECV(3)				     Open MPI					  MPI_ISENDRECV(3)

MPI_Isendrecv — Sends and receives a message.

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Isendrecv(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_Request *request)

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

   Fortran 2008 Syntax
	  USE mpi_f08
	  MPI_Isendrecv(sendbuf, sendcount, sendtype, dest, sendtag, recvbuf,
		  recvcount, recvtype, source, recvtag, comm, request, 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_Request) :: request
	      INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS
       • sendbuf: Initial address of send buffer (choice).

       • 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).

OUTPUT PARAMETERS
       • recvbuf: Initial address of receive buffer (choice).

       • request: Communication request (handle).

       • ierror: Fortran only: Error status (integer).

DESCRIPTION
       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. The two (source and destination)  are  possibly
       the  same.  This	 operation  is	useful	for  executing	a shift operation across a chain of processes. The
       send-receive operation 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.

       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_Isendrecv executes a non-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, and may
       have different lengths and datatypes.

       A non-blocking send-receive request can be determined to be completed by calling the MPI_Wait  <#mpi-wait>,
       MPI_Waitany  <#mpi-waitany>,  MPI_Test <#mpi-test>, or MPI_Testany <#mpi-testany> with the request returned
       by this function.

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>/MPI_Init_thread  <#mpi-init-thread>,
       after  MPI_Finalize  <#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	<#
       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>/MPI_Comm_spawn_multiple	<#
       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 <#mpi-abort> was called on that communicator. If called
	 on a window or file, acts as if MPI_Abort <#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	 <#mpi-comm-create-errhandler>	   then	    MPI_Comm_set_errhandler	<#
	 mpi-comm-set-errhandler>

       • MPI_File_create_errhandler	<#mpi-file-create-errhandler>	  then	   MPI_File_set_errhandler	<#
	 mpi-file-set-errhandler>

       • MPI_Session_create_errhandler	 <#mpi-session-create-errhandler>   then   MPI_Session_set_errhandler	<#
	 mpi-session-set-errhandler> or at MPI_Session_init <#mpi-session-init>

       • MPI_Win_create_errhandler	<#mpi-win-create-errhandler>	  then	    MPI_Win_set_errhandler	<#
	 mpi-win-set-errhandler>

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

       See the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>.

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

       See also:

	  • MPI_Isendrecv_replace <#mpi-isendrecv-replace>

	  • MPI_Sendrecv <#mpi-sendrecv>

	  • MPI_Sendrecv_replace <#mpi-sendrecv-replace>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026					  MPI_ISENDRECV(3)
